Lupins and alliums are classic cottage garden plants for May – their contrasting shapes work beautifully together Image: Shutterstock
May is a fabulous time in the garden – fresh spring foliage is injected with colour from early herbaceous perennials, tulips give way to alliums and iris, whilst numerous flowering shrubs such as rhododendrons, viburnum and weigela launch into bloom and the air is perfumed with lilacs. At the end of the month the world’s greatest flower show returns at Chelsea, inspiring gardeners for another busy season.
To keep up with your garden tasks, turn to my jobs to do in May blog . But before you roll you sleeves up and get stuck in, let’s have a look at some of this month’s best plants!
Lilac ‘Palibin’ (Syringa meyeri ‘Palibin’)
Lilac ‘Palibin’ Image: Canva
This dwarf lilac is an old cultivar dating from around the early 1900s where it was already a popular garden plant in China before its discovery by Western collectors. ‘Palibin’ is quite different from the large and domineering common lilac. Slow growing, it will take up to 10 years to reach its maximum height and spread of 1.5 metres but will flower in abundance at an early age, making a perfect specimen for a container or small border. It lends itself to growing as a standard or bush form. Unlike the large, heart-shaped leaves of common lilacs, ‘Palibin’ has small, delicate, slightly leathery oval leaves which give it added value throughout the season. In spring, deep purple buds open to lavender-pinkish airy panicles. The individual flowers are small but numerous and intensely scented.
Clematis macropetala
Clematis macropetala Image: Canva
It’s easy to be seduced by the large, showy flowers of later clematis, but the early varieties have exquisitely delicate blooms, are a valuable source of nectar for pollinating insects emerging from hibernation and don’t require any routine pruning. The nodding, semi-double blooms of Clematis macropetalaare borne in abundance and make an exceptionally dainty feature scrambling up a wall or trellis.
Geum ‘Totally Tangerine’
Geum ‘Totally Tangerine’ Image: Thompson & Morgan
Geums are valuable perennials for their early flowering and I love the way their ruffled flowers hover on long stems, dancing in the breeze. ‘Totally Tangerine’ wins my vote for the best variety. It is extremely long flowering and after its main May/June performance it continues to produce more flower buds below the earlier spent flowers. The flowers are sterile and so they don’t waste energy on seeding or demand dead-heading. The blooms are not a brash orange but a soft-apricot with subtle variations in tone. This means that they are easily combined with absolutely any colour – although they look especially stunning with purple alliums.
Aquilegia ‘Nora Barlow,
Aquilegia ‘Nora Barlow’ Shutterstock
Aquilegias are one of those happy plants which look incredibly delicate but are as tough as old boots, growing in sun or shade and in any soil type. Their nodding flowers are held on long, graceful stems above a mound of feathery foliage. They don’t take up too much space and can be easily dotted in between other perennials to fill gaps. ‘Nora Barlow’ is an old variety with fully double flowers flushed red, pink and white. If allowed, it will throw up seedlings which will generally come true.
Astrantia major ‘Moulin Rouge’
Astrantia ‘Moulin Rouge’ Image: Sempra
A perfect partner for aquilegias, and equally well-behaved, are astrantias. If you haven’t grown astrantias before then you are missing out. The flowers of Astrantia ‘Moulin Rouge’ are distinctive from other flowering perennials. This is not plant which shouts for attention, but deserves close appreciation of its intricately detailed flowerheads, with maroon papery bracts surrounding a central pincushion. The deeply lobed leaves are also a handsome feature. Prefers a rich, moist soil.
Rhododendron ‘Blue Tit’
Rhododendron ‘Blue Tit’ Image: Morley Nurseries
May is the time to visit woodland gardens when showy rhododendrons are out in force. These large specimens may be beyond the scope of most of us, but we can still enjoy the dwarf varieties. Rhododendron ‘Blue Tit’ is smothered in masses of clear, violet-blue flowers and is perfect for acid borders in sun or partial shade or as a feature in spring containers. Its dark, evergreen leaves provide useful background foliage for the rest of the season.
Annelise Brilli is the Horticultural Copywriter for Thompson and Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.
Zinnia varieties come in deliciously fruity shades Image: Canva
I’m an unabashed lover of zinnias. There is something about the luminosity of their colours and their unique shape – a ruff of stiff petals surrounding a central cone which is crowned with star-shaped golden florets – which I find irresistible. But when I mention zinnias so many people shake their heads and say they have no end of trouble growing them from seed. But they’re actually easy. All you need to do is observe one simple rule!
How to grow zinnias
Zinnias like this ‘Purple Prince’ are members of the daisy family. The centre of the flower is composed of hundreds of tiny, golden, star-shaped florets. These tiny flowers open from the outside towards the centre, forming a raised central cone encircled by stiff petals. Image: Canva
Zinnias come from Mexico. They are hot season plants which loathe chilly days and nights as well as fluctuations in temperature between the two. As they are half-hardy annuals, many people sow them in February or March, thinking that they need a long growing season and that they will get ahead by sowing them early. What actually results is sad-looking seedlings which just sit and sulk. Before long their leaves curl up in disgust and go brown with botrytis (grey mould) infection.
Ipomea (Morning Glory) are similar in this regard. They resent fluctuations in day and night time temperatures and like it warm throughout the day and night. Expose them to cool nights and they soon develop sickly white patches on their leaves.
Not all zinnias are jazzy, they also come in delicate pink and peach shades such as this charming ‘Zinderella Peach’ which features a large ruffled centre. Image: Thompson & Morgan
To grow zinnias successfully from seed, always delay sowing until the end of April or first week of May. It may seem late but the seedlings will germinate very quickly – within one to two weeks – and will grow on strongly. Seeds sown earlier will still be flailing whilst later ones rapidly catch up and overtake them.
Sow one or two seeds into separate modules filled with free-draining seed compost. They resent root disturbance and so modules are the best method. You can sow them direct outdoors but I find indoor sowing more successful as slugs love the seedlings. If you sow 2 seeds per plug and both come up then carefully remove the weaker seedling whilst holding the other good seedling in place by pressing your finger alongside it.
I sowed these Zinnia on the 1st May and by the end of June they were strong healthy plants with good roots systems which were ready to go into their final planting positions Image: Annelise Brilli
Once the roots of your zinnia seedlings have filled their plugs, pot them on into larger pots – I use 9cm ones. Don’t bury the stem deeper in its new pot – this reduces the chances of stem rot. The timing of potting up is crucial. Too early and the plugs won’t drop neatly out of their modules. This will disturb the roots and put a check on their growth. Too late and your seedlings will become pot bound. Pot bound seedlings fail to recover, remaining permanently stunted for the rest of the growing season.
When your seedlings are a few inches tall, pinch out the growing tips to encourage bushy plants. As soon as the root system has comfortably filled up the pot and is just beginning to poke out of the drainage holes, they are ready to plant out. Again – don’t leave it until they are pot-bound! If you sow them late April to early May, then they’ll be ready to plant out at the end of June by which time all risk of frost will have passed. Plant them into freely-draining soil in a sunny position about 23-30cm apart. Water them well afterwards. The large-flowered varieties may require staking.
Zinnias as cut flowers
Zinnias make long lasting cut flowers Image: Shutterstock
Zinnias make fabulous cut flowers. They have long, sturdy stems and long-lasting blooms. The single coloured varieties make excellent matches for the jewelled hues of snapdragons (antirrhinums), salvias, dahlias and salpiglossis.
Zinnias in the veg garden
Image: Canva
Zinnias look at home in the veg garden, providing welcome pops of colour amongst leafy vegetables and associating well with other potager annuals such as sunflowers. The single flowered varieties are also attractive to beneficial insects such as hoverflies.
Single varieties of zinnia attract plenty of pollinators Image: Shutterstock
Zinnias in borders and containers
Zinnia ‘Red Spider’ has smaller, finer flowers Image: Shutterstock
Zinnias bring intense colour in late summer and autumn and are good for filling gaps in borders or extending displays after most perennials have finished. They also lend themselves to hot-themed tropical borders alongside the luxurious purple leaves of the castor oil plant (Ricinus communis), dahlias and cannas.
Compact varieties such as ‘Red Spider’ are also available. These have smaller, more delicate flowers which are good candidates for edging borders and associate well with ornamental grasses. Zinnias also perform well in container displays alongside other summer bedding.
Combine zinnias with other hardy and half hardy annuals to make gorgeous vase displays. Here they are displayed with Antirrhinums (Snapdragon), marigolds, Celosia cristata, Rudbeckia and Ageratum Image: Shutterstock
Problems
Zinnias like it hot and dry and will succumb to grey mould if it is wet and humid. There isn’t much to be done about this except keep your fingers crossed and hope for a good summer!
Take a look at our selection of zinnia seeds and get sowing now. They will hold their dazzling flowers through summer and autumn, providing zingy colour when everything else looks drab. Keep dead-heading them and you will get armfuls of colourful blooms for indoor displays too. You can find lots more ideas for your summer garden over on our summer flowers hub page.
Annelise Brilli is the Horticultural Copywriter for Thompson and Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.
The garden is really racing ahead and it’s a job to keep up with it. Getting on with tasks now will enhance your summer displays, but don’t forget to give yourself some time to relax outside and just enjoy it!
Bedding
Summer bedding is perfect for plugging gaps in borders Image: Shutterstock
Spring bedding will be fading and it’s time to switch to summer varieties. If you live in cold parts of the UK and you don’t have a greenhouse or cold frame then you will need to resist the temptation to buy these frost-tender plants too early. Tender bedding plants need to be gradually acclimatised to outdoor conditions after purchase, but you can save yourself the hassle with our Garden Ready plants which have already been hardened off for you. Our pre-planted hanging baskets are also great time-savers.
Greenhouse
Open up the doors and vents in your greenhouse as much as possible Image: Canva
It can get really hot in the greenhouse so ventilate it as much as possible. Invest in a maximum /minimum thermometer and keep an eye on temperatures. Ideally, you don’t want them to climb above 80 °F or 26 °C. When a greenhouse gets too hot plants stop growing, become stressed and succumb to pests and disease. Aphids, whiteflies and red spider mite will quickly take hold and multiple rapidly in these high temperatures.
In an overheated greenhouse small seedlings can be frazzled incredibly quickly. Seedlings which have just been pricked out are especially vulnerable and it’s important to have a cool, shady spot for them somewhere. Cool down your greenhouse and protect your seedlings by painting some greenhouse shading on the glass. I tend to paint shading onto one side of my greenhouse, which I use for seedlings, but leave the other side for my sun-loving succulents. The other way to cool an over-heating greenhouse is by ‘damping down.’ This simply means flooding the floor with water which will cool the greenhouse quickly by evaporation.
Feeding
New trees and shrubs will appreciate a spring feed with granular fertiliser Image: Shutterstock
Container plants
At this time of the year winter rains have washed a lot of nitrogen out of the soil and plants may start to look hungry and exhibit yellow leaves. Specimens which have been permanently growing in containers will have used up all the nutrients in their compost and can struggle to put on new, leafy growth. Top dress them with a balanced fertiliser which includes trace elements such as Vitax Q4.
Bedding
When potting up seasonal containers and hanging baskets, professional gardeners always incorporate slow-release fertilisers into the compost. This saves an enormous amount of time on applying liquid fertilisers. Liquid feeds can be useful as a top up but are more wasteful as much of the feed simply drains out of the pot. They also tend to result in inconsistent feeding, promoting surges of soft, sappy growth. Try using a controlled release product such as Incredibloom instead – it will continue to feed your plants for about 7 months.
Roses
Feed hungry roses with a proprietary rose feed now. These contain high levels of potassium to promote flowering.
Pelargoniums (Geranium)
Pelargoniums will also benefit from a flower-boosting high potash feed. Avoid giving them nitrogenous feeds, which will encourage the production of leaves over flowers and create soft growth which is more vulnerable to fungal diseases.
Plant supports & ties
Tall plants like Delphiniums are best supported early on Shutterstock
Herbaceous borders
Plants are growing rapidly and it’s important to get them supported as quickly as you can. If you are like me, you probably tell yourself this every year, promise to do it next weekend, and then, before you know it, the plants have shot up, the first rain storm hits and everything falls over into a mess! It’s a wise idea to purchase some supports early on so you can avoid getting yourself into this pickle.
Climbers
All your other climbers, such as climbing roses and clematis, will need regular tying in. Sweet peas left to trail along the ground not only grow poorly but are targets for slugs and snails so tie them onto their canes or obelisks early on. I prefer natural jute twine as it’s biodegradable and blends in unobtrusively. Tie the twine in a figure of 8 allowing room for the plant stems to expand. I like to put the string around the plant stem first and then wind it around the support twice. That way you can hide your knots on the back of the support and the tie won’t slide up and down.
Watering
New trees and shrubs should be ‘puddled in’ on planting and watered frequently during dry weather Shutterstock
Springs have become increasingly dry and the recent weather has been warm but windy. This combination of high aerial temperatures and wind really licks the moisture out of plants and can quickly desiccate them.
Before you plant new plants, soak the root ball by plunging them into a bucket of water. After planting, water them regularly in dry weather. It is best to give plants a generous soak at longer intervals rather than frequent but sparse watering which only encourages surface rooting. Once the root balls of containerised plants have dried out underground they tend to repel water and can remain surprisingly dry after watering attempts, so aim to keep them moist.
Pruning
Cut out a proportion of the old stems from early spring flowering shrubs such as this Ribes (flowering currant) Image: Annelise Brilli
Early spring-flowering shrubs
Prune established spring- flowering shrubs such as forsythia, Ribes (flowering currant), Spiraea ‘Arguta’ (bridal wreath), Exochorda (pearl bush) and Kerria japonica. These shrubs flower on growth produced in the previous year and so they need to pruned immediately after flowering.
You can take out up to one third of the oldest stems, cutting them back to a shoot/bud near the base. Pruning out the oldest stems will encourage the formation of new ones so that the wood is continually renewed. With Kerria japonica you can cut back all the previously flowered stems.
You can also trim back the top of stems to keep them tidy but bear in mind that these shrubs have an arching habit which you don’t want to ruin. Always try to prune them back to a convenient shoot lower down rather than leaving stubs.
Japanese Quince
Chaenomeles (Japanese quince) has a twiggy rather than arching habit. Shorten the new growths to encourage the formation of lots of short, flowering spurs.
Evergreen shrubs
Inspect evergreen shrubs and prune out any frost damage.
Pyracantha
Wall trained pyracanthas can be pruned back now, reducing outward-facing shoots to a few inches and removing completely any shoots growing into the wall. This will inevitably remove some flowers but it will promote the formation of short spurs which will become crowded with future flower buds and berries.
Dahlias, cannas and other tender perennials
Dahlia tubers should be shooting well by now Image: Shutterstock
Harden off your tender plants which you have been overwintering in a frost-free place. Plant them out when all danger of frost has passed. This is always a gamble but generally you should be safe by the end of the month.
If you don’t see signs of growth on your tender perennials don’t give up on them too soon -they are slow into growth. All the top growth of tender Salvias may completely die off but don’t throw them away in haste – many varieties will re-sprout from the base.
Chelsea Chop
The Chelsea Flower Show is a reminder to do the ‘Chelsea Chop’ Image: Shutterstock
Enjoy the Chelsea Flower Show which runs from 24-28th May this year, and use it as a reminder to try out a pruning technique called ‘The Chelsea Chop’.
If you want to keep your herbaceous perennials shorter, sturdier and more compact, you can chop them back by up to a half in late May or early June. This pruning technique will produce plants with shorter, self-supporting stems and more (but usually smaller) flowers. Not all perennials will respond to this treatment but those which do include: Asters, Echinacea (coneflower), Helianthus x laetiflorus (perennial sunflower), Hylotelephium (Sedum), Monarda (Bergamot), Nepeta (Catmint), phlox and rudbeckia.
Seed sowing
Sow flowering annuals in rows the same way as you would with vegetables Image: Canva
The soil is lovely and warm now and hardy annuals can be sown directly into the ground. Rake the soil well to make a fine tilth and sow them in rows. Sowing in rows makes it much easier to distinguish between your flower seedlings and weed seedlings. Once the seedlings have grown and you have thinned them out, you won’t notice that you originally sowed them in straight lines.
Thin out/pot on any annuals sown earlier.
It’s a bit late now to sow most tender annuals – best to buy them as ready-grown plugs.
Biennials such as Wallflower ‘Scarlet Bedder’ can be sown this month Image: Canva
Don’t forget to sow biennials for next years bedding plants. Wallflowers like the sumptuous ‘Scarlet Bedder’ and dainty forget-me-nots will make fabulous partners for next year’s tulips. Pansies sown now will provide vibrant colour in the winter, whilst Bellis perennis ‘Pomponette’ will grace window boxes and border edges with bright pom poms next spring. For cut flowers, you can’t beat clove-scented Sweet Williams (Dianthus barbatus).
Foxgloves are cottage garden staples and great for bees Image: Canva
If you are looking for some flowers for the wildlife garden, foxgloves will provide plenty of food for foraging bees. They should be sown now on the surface of trays of fine compost or in a patch of spare ground. The tiny seeds are like dust and shouldn’t be covered – they won’t come up if you do! Sweet Rocket (Hesperis matronalis) will also attract pollinating insects with its sweetly fragrant blooms.
Lawns
A drop spreader is a useful tool for fertilising large lawns Image: Shutterstock
Fertilise
Apply spring fertiliser to lawns. If you only have a small to medium family lawn ecofective Lawn Feed is an organic treatment which will treat up to 150 square metres and is safe for pets and children. For large lawns, Sportsmaster Spring & Summer is a high nitrogen, slow-release formula which you can use all growing season.
Try to keep your use of weedkillers to a minimum. Remove deep weeds by hand or spot treat them. If you are going to resort to chemicals, it is much more effective to use a separate fertiliser followed by a weedkiller product, such as Weedol, rather than a combined treatment. Fertilising first boosts the grass in its competition with the weeds, enabling it to quickly grow into gaps after treatment. Meanwhile the weeds will put out more leafy growth, which will absorb more weedkiller.
Mow
Keep mowing your grass every week, gradually reducing the height of cut as the weather gets warmer. Better still – stop mowing and weedkilling altogether! And join in with No Mow May – see below.
Pest control
Avoid using chemical pesticides which are not only harmful to your enemies but also your garden allies such as this aphid-munching ladybird larva Image: Canva
All this warm weather means that pests are rapidly multiplying. Use environmentally friendly sprays such as ecofective Bug & Mildew Control to keep on top of aphids, black fly and red spider mite.
Whitefly in greenhouses can quickly become a real problem, so introduce the parasitic wasp, Encarsia formosa, before pest populations build up.
Treat roses with a preventative anti-fungicidal spray before blackspot, rust and mildew take hold.
Clematis
Keep tying in clematis but use natural twine, which biodegrades, rather than this plastic coated wire. Image: Shutterstock
Regularly tie in clematis to its support.
Clematis montana does not need regular pruning but if it’s getting out of hand in a confined space you can trim it back now and remove any dead or diseased growth.
Plant propagation
Softwood cuttings should be about 3-5 inches (7.5-12.5cm) long Image: Canva
Take softwood cuttings from hardy perennials, shrubs and tender perennials such as pelargoniums and osteospermums. Although softwood cuttings should be pliable, the very softest growth will often wilt quickly and is less successful. Wait until the material has firmed up slightly and gives a little snap when you bend it.
Once they have finished flowering, cut back and divide spring flowering perennials such as Pulmonaria (lungwort), Doronicum (leopard’s bane), Brunnera (Siberian bugloss) and primulas.
Rock plants
If you don’t prune aubretia after flowering it will become straggly and bare at the base Image: Shutterstock
Spring flowering rock plants such as alyssum, arabis and aubretia should be cut back hard now to keep them trim and tidy.
Early spring bulbs & flowers
Dead head tulips and daffodils so that they don’t waste energy on developing seed. Image: Annelise Brilli
Continue dead-heading daffodils and tulips but leave the foliage intact for at least 6 weeks after flowering. It is not worth doing this to ‘bedding’ tulips, which decline after the first year, but some tulips, such as Darwin hybrids, are reliably perennial and will continue to flower again next year.
Once the foliage is yellow, lift congested daffodils which didn’t flower well this year and replant them.
Fading spring bulbs which you want to keep for next season can be lifted and transplanted elsewhere to make space for summer bedding. Feed all your spring bulbs now, preferably with a low nitrogen, high potash feed.
Pulmonaria (lungwort) and Brunnera (Siberian bugloss) invariably get mildew at this time of the year. Simply cut all the foliage off and give them a good water and they will reward you with healthy new foliage.
Wildlife Gardening
Plants such as this Calendula (pot marigold) are important sources of food for foraging insects Canva
Gently clear the pond of pond weed leaving the debris on the side so pond creatures can easily crawl back in.
“Join legions of gardeners and say “no” to the mow this May to help our bees, butterflies, wildlife and us!” says Plantlife. You don’t have to do much. Nothing in fact. Just relax in a garden armchair and let the wild flowers in your garden provide a feast for hungry pollinators. You might be amazed at what pops up in your lawn when you stop mowing. Instead of telling yourself that there’s nothing you can do to help the planet, do just this one simple thing and help to reverse the drastic decline in our insect populations.
Annelise Brilli is the Horticultural Copywriter for Thompson and Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.
The sight of tender shoots pushing through warming spring soil lifts the heart of every gardener. After weeks of anticipation the garden is finally moving. We rush to the greenhouse and start frantically sowing, gleefully admiring trays brimming with new seedlings. Hoes and rakes are joyfully unleashed from dark sheds, the soil is tilled, seeds are scattered. At the end of the day, as sunlight rakes across our tired but satisfied brows, visions of perfect lettuces, juicy peas and drifts of flowering annuals dance before our eyes. Spring – the season of optimism!
But behind that optimism is a hidden anxiety. There is something nasty lurking under the leaf litter at the back of your mind. And suddenly, in one damp night, swathes of innocent baby seedlings are ruthlessly massacred, eager buds nipped off in their prime, precious young shoots ripped to shreds. Yes! Those monstrous molluscs have returned: Slugs and snails.
Spring into action against slugs and snails
These seedlings are soft and leggy and provide excellent fodder for slugs and snails Image: Canva
As temperatures rise, slugs and snails emerge from hibernation where the ability to super-cool their bodies has protected them from freezing. Meanwhile, generations of eggs laid in the autumn are busy hatching throughout April and May. All of these animals emerge with raging appetites and, as the spring garden serves up a banquet of soft and succulent food, who can blame them for gorging at the feast?
From 1 April 2022 it is now illegal to sell and use metaldehyde slug pellets. So, whether you like it or not, this particular weapon can no longer be part of your armoury against the gardener’s number one enemy. British gardeners have been using some 650 billion slug pellets per year – and there is no doubt about it – they worked. Sadly, they worked rather too well. Only a small amount of metaldehyde is needed to poison or kill non-target animals and as the pellets included a bait, every animal which occupies your garden – birds, frogs, toads, newts, hedgehogs, slow worms, mice, even your pets – was at risk.
The good news is that there are many alternative and safe slug and snail deterrents. But which actually work? Being prepared in advance of the enemy is crucial – so let’s examine the options – both silly and sensible – and whilst we’re at it, take a closer look at these much-maligned molluscs, delving into dark, damp corners to uncover some of their slimy secrets.
Hand to hand combat
Some gardeners are more ruthless than others! Image: Shutterstock
Post-war gardeners were made of stern stuff. My mum would pluck a slug from the ground, confront it eyeball to eyestalk and then abruptly slice it in two with her secateurs. I don’t count myself as a squeamish gardener, but this is a bit too much for my stomach. Neither am I that fond of her other strategy: the nightly ritual of slug-stalking with a salt cellar which the following morning would leave hazardous pools of slug-gloop along the path awaiting my young unshod feet.
I am however partial to the satisfying scrunch of crushing snails beneath my boot. But I confess to being a cowardly killer, as I prefer not to look too closely at my victims as they flinch under my boot. As well as their eyes, snails have light sensing cells dispersed all over their outer skin which enables them to quickly react to the hovering shadow of a murderous hand or boot. Other suggested molluscan murder methods include collecting them all in a bucket. Exactly what you do with your bucket of slugs and snails afterwards I do not know or care to contemplate.
Slugs lay up to 200 eggs per square metre Image: Shutterstock
Are these methods effective? Well, they certainly satisfy the gardener’s thirst for revenge. But do they make any significant dent in the population of molluscs which are busy consuming your garden? The problem is, although you may not find these molluscs attractive, they find each other positively irresistible. Both slugs and snails are hermaphrodite, which is a distinct advantage for such slow animals that might otherwise have difficulty bumping into the ‘right’ partner; and both enjoy very elaborate courtship rituals which can go on for hours. In fact, gastropods have voracious appetites for love as well as food and can boast of very adventurous sex lives, so adventurous that the next time I look a snail in the eye both of us might blush. All this romance means that the average garden has 20,000 slugs and lay as many as 200 eggs per cubic metre. So I’m afraid you may have won the battle, but the slugs have definitely won the war.
Create a slug zone
Slugging it out with a bucket load of slugs is not for the faint hearted Image: Shutterstock
One suggestion I have come across on the internet is to ‘deliberately attract slugs’ to an area of your garden away from your target plants and then to go out and collect them at night. Gardeners World suggests “using something they’re attracted to – old veg leaves, dried cat food, bread rolls, oats or bran”. To me, this sounds like a very good way of attracting rats as well as molluscs and given that rats have a considerable speed advantage, I suspect that both slugs, snails and the gardener are likely to end up disappointed by the results.
It also raises the same tricky problem encountered above – what do you do with your bucketful of slugs and snails? One traditional solution has been to lob them over the neighbour’s fence. If you are having a boundary dispute with your neighbour this will probably give considerable satisfaction, until that is, those cunning slugs and snails find their way home. Unfortunately, scientists have discovered that snails are equipped with a homing instinct. This means they need to be hurled at least 20 metres away to ensure they won’t find their way back – a feat which would require the arms of an Olympic shot putter.
I’m left with a sinking feeling that this project is doomed to backfire – the neighbour is enjoying a garden freed of slugs, snails and rats whilst I’m saddled with a bucketful of slimy slugs and snails and a cold walk in the night to dispose of them.
Beer Traps
Research by Garden Organic found that slugs enjoy beer but turned their tentacles up at red and white wines, Cava, cider, orange squash and water Image: Shutterstock
Beer traps are a well-known traditional slug and snail deterrent but they are a method which I definitely can’t advocate. Slugs and snails can sniff out fermenting beer from long distances and will be attracted to your boozy garden often without actually drowning in the beer, so you are likely to end up with a bigger population of molluscs than you started with. Meanwhile, a host of other beneficial insects will also be attracted to your traps and meet a sticky end. Personally I think it’s a waste of beer. Let’s move on!
Disappointingly, natural home-made barriers such as wood ash are less than useless on slugs and snails Image: Shutterstock
Sorry, but all of these methods are perfectly useless. This is because slugs and snails are equipped with a super power: slime! Acting as both an adhesive and a lubricant, this slime has miraculous elastic properties and the ability to change its consistency when pressure is applied. Get slug slime on your skin and you will find it a devil to wash off due to its supreme stickiness and impressive ability to hold water. Scientists have even taken inspiration from slug slime to develop medical glues which will bond wet tissues and stem bleeding. Even hedgehogs find slug slime troublesome to deal with. This video by Julia from The Hedgehog Diaries shows a hedgehog de-sliming its slug meal by rolling it on the ground!
Dr Hodgson of Exeter University has discovered that snails use up to 30 percent of their energy in slime production and reports that ‘snails move in convoys, piggy-backing on the slime of other snails to conserve energy’. Slime not only assists movement but is also designed to prevent injury when molluscs move over rough surfaces. Their sublime slime means that slugs and snails can happily glide across razor blades and they will be laughing off your puny human efforts to deter them with mere eggshells.
Slime is a super power! But wool pellets are an effective weapon Image: Shutterstock
Put aside your eggshells and coffee grounds and try wool pellets instead. If you find wool jumpers itchy, then so do slugs! Wool fibres are highly hygroscopic, meaning they absorb moisture. This, plus natural sands and grits in the wool and salts from sweaty sheep, sucks up slime and causes irritation to the slugs so they crawl off in search of easier food.
After placing them around the base of the plant the pellets are thoroughly watered. This causes them swell and bind together forming a dense matt which isn’t disturbed by wind or rain. Although wool pellets are quite pricey the mat will last for up to 12 months and has the bonus of acting as a mulch which will supress weeds and retain moisture, breaking down naturally in the soil to slowly release nutrients.
I planted out a lot of sunflower seedlings last year and tired of watching each one being felled by marauding molluscs I tried wool pellets. I’m pleased to report that they were a resounding success. They need to be piled up in a wide, thick barrier ( at least 4inches (10cm) wide and a few inches deep) so are good for protecting individual specimens such as hostas, delphiniums, sweet peas and lupins but not so useful for long rows of seedlings.
Grazers is available as a concentrate or a ready-to-use spray Image: Thompson & Morgan
Grazers offer a range of organic pest-deterrents in a liquid form which are based on calcium, with different formulations tailored to different pests. I’ve certainly had success using Grazers to deter rabbits and pigeons, so their slug and snail formula looks a promising bet. What I have found is that for Grazers to be successful you need to apply it thoroughly and repeat spray at intervals. How often you need to re-apply will largely depend on rainfall, time of year and growth rates so it varies from several days to a few weeks. Fast growing young plants with soft tissues which are subject to heavy spring rains will need more frequent applications. If you are only treating one or two plants then a handheld sprayer is fine but keen gardeners would be well to invest in a pressure sprayer for this task. This allows you to make up a tank of mix and then grab it and speedily spray your vulnerable plants whenever required.
The calcium contained in Grazers is absorbed through plant leaves and stems into plant cells. It doesn’t kill slugs and snails but makes plant tissues distasteful so they will seek other food sources. It takes a little while for the calcium to be absorbed and moved through the plant, so if you are transplanting vulnerable young plants from the greenhouse to their outdoor positions, it’s a good idea to treat them with Grazers for a few days prior to doing so. Price wise, Grazers is a relatively economic option, but it obviously requires more labour than putting down wool pellets. However, it’s better suited to large areas of crops or ornamentals.
A note on gastropod grazing habits
Not for nothing are slugs and snails known as ‘gastropods’ – literally an ‘eating foot’. These animals have evolved into highly efficient munching machines and they are not easily put off their meals. Grazers is the only commercial product which makes plant tissues distasteful to them. Both slugs and snails are equipped with a ribbon-like tongue called a radula which is covered in thousands of tiny teeth, neatly arranged in rows. In fact, the garden snail has about 14,000 teeth! By grinding the radula against its horny jaw, the slug or snail rasps at its food. This causes the ragged abrasion of plant surfaces which is characteristic of slug and snail damage. It also enables them to grind their way through tougher foods like your potato tubers. They may lose a few teeth in the process, but new ones quickly regrow in their place. Once past the mouth food enters a holding bay or ‘crop’ so slugs and snails can happily ‘eat on the run’, bolting down your entire tray of seedlings, rapidly followed by seconds and pudding before retreating beneath the tray to digest dinner at leisure, in the dark and hidden from predators.
Organic-approved slug pellets
Even organic-approved slug pellets should be used sparingly, not like this! Image: Shutterstock
What’s in organic slug pellets and how do they work?
Numerous brands of organic-approved slug pellets are available including:
All of these products are based on ferric (iron) phosphate which is bound to a cereal-flour based bait. Iron phosphate affects the metabolism of calcium in the gut of slugs and snails causing them to stop feeding and die within three to six days. Any uneaten pellets will slowly break down releasing phosphate and iron which will be taken up by plants as nutrients.
Effect on earthworms
These pellets are harmless to mammals but there is one downside – they can be harmful to earthworms. As well as ferric phosphate, the pellets contain chelating agents which are toxic to earthworms that consume them, causing them to feed less, lose weight and die. The power of humble earthworms in maintaining a healthy soil ecosystem is not something to be casually dismissed, so it is essential that gardeners use these pellets responsibly.
Application
I wince when I see people pour gluts of pellets all over the place as this really isn’t necessary – the pellets are baited and so will attract slugs and snails to them. These molluscs are equipped with incredibly sensitive taste and smell organs in their lips and tentacles which can detect minute chemical traces in their environment. Slugs and snails find potential mates by sniffing out and following mucus trails and will back track along their own scented trails to find their way home. So, if you are going to use organic slug pellets, do so sparingly, just using 4 or 5 in an area the size of an A4 piece of paper.
Nematodes: a slug’s nemesis
Magnified image of a nematode worm Image: Canva
What are nematodes and how do they work?
Professional gardeners have been using living organisms to control pests, known as ‘biological control’, for many years. They are now readily available to amateur gardeners, and if you haven’t tried them yet then you are definitely missing a trick! Nematodes are microscopic worms which are naturally present in the soil and act as parasites on other living organisms. The great thing about them is that they are host-specific and so non-target species are left unharmed.
Slugs infected by nematodes develop a swollen mantle Image: Ion Colino – http://areitzsoroa.blogspot.co.uk/2010_12_05_archive.html, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=55026740
There are nematodes for a whole range of pests and they all have distinctly unpronounceable and forgettable names. Phasmarhabditis hermaphrodita is the one for slugs, conveniently sold under the moniker ‘Nemaslug’. These tiny worms with a big name are certainly the slugs nemesis. They enter the slugs body through its breathing pore, multiplying rapidly and causing them to develop a swollen mantle. The sick slug immediately goes off its food and often remains underground. So, although it takes between 7 to 21 days for it to keel over and die, damage to your precious plants is immediately reduced. Once the slug dies the nematodes tuck in and feed off its remains. They go on to produce another generation of hungry slug-killers which travel through the soil to hunt down new slug hosts.
Application and timing
Nemaslug is effective but it must be applied correctly and timing is crucial. The sachet containing the nematodes is mixed into water and applied onto the soil using a watering can or garden hose applicator. The soil temperature needs to be consistently above 5°C but you also want to apply it as early as possible in the spring to catch the first generation of young slugs before they turn into larger adults which are more resistant to infection. One application provides up to 6 weeks of control so, several applications are needed during the growing season. As Nemaslug is a live product with a shelf life, (it has to be stored in a refrigerator on receipt), the packet includes a small calendar to record applications and remind you when to order your next batch.
Good against slugs but not snails
Nematodes attack all slugs but are not very effective on snails, such as these attractive brown-lipped ones Image: Canva
Nemaslug is effective on all pest slug species and grey field slugs are especially susceptible which is good news as they are the most damaging of all garden slugs. However, if snails are your biggest enemy then Nemaslug won’t be much use. Although nematodes can kill snails, they tend to evade infection due to their largely surface-dwelling nature.
Being ugly, slimy and homeless, slugs have few fans, and seem to come in for the most blame. Meanwhile the snail, with its ingenious and pretty armour, its shy ‘peak a boo’ behaviour and the fact that the shell provides a convenient and dry hand hold for curious humans, has a slighter cuter reputation. However, of the 30 plus species of slugs in Britain, only 4 are really garden pests feeding off living plant material, the remainder prefer munching on dead organic matter. If you have a limey soil, point the finger of blame at snails instead. They prefer calcareous soils which provide the necessary calcium to build their shells.
Not so effective on heavy soils
Nemaslug is more effective in freely draining soils than heavy clays, as these allow nematodes to easily move about and find their hosts.
Harmless to earthworms
Nemaslug has the advantage over organic pellets in that it continues to work well in wet weather and numerous experiments have demonstrated that it is completely harmless to earthworms along with insects and other organisms.
Slug and snail control: A military strategy
Use a combination of methods
In the war against slugs and snails it pays to have a co-ordinated strategy, employing all of your cultural, chemical and physical controls to defeat these resilient garden adversaries. Don’t rely on just one of the methods above, which all have their advantages and disadvantages, but use them in tandem. Use an early application of nematodes to protect vulnerable root crops, such as potatoes, across a wide area of ground. Apply Grazers to leafy veg such as brassicas. Meanwhile, protect your ornamentals with Ferric phosphate and wool pellets.
Grow your seedlings on
Grow seedlings on until they have reached a reasonable size and their stem and leaf tissues have toughened up a bit before planting them out. Greenhouses can quickly get too hot in spring sunshine even when the ambient temperature is cold. Seedlings raised in excessively warm conditions grow very soft and leggy – perfect food for slugs and snails. Ventilate your greenhouse as much as possible to keep temperatures at a reasonable level and harden off seedlings in a slug-protected area (see below) before they go outside.
Concentrate your efforts
Pay especial attention to your nursery areas where seedlings and young plants are placed and concentrate your efforts on these zones, using Ferric phosphate pellets sparingly to protect them. Reduce any hiding places in these areas by keeping them tidy and removing debris and leaves. Pay attention to crop margins which are adjacent to nearby cover such as hedges or long grass.
Check your seed trays
Slugs and snails love to hide beneath seed trays and pots so check underneath them everyday.
Don’t use high nitrogen fertilisers too much
Slugs and snails will go for soft juicy growth which is exactly what high nitrogen fertilisers promote. Aim instead for slow, steady growth. Where necessary use organic slow-release fertilisers or specialised feeds such as Chempak Low Nitrogen (good for firming up vegetables and vulnerable plants such as lupins and delphiniums), or Chempak High Potash (to encourage flowering rather than leaf and stem growth).
Water in the morning
This will enable the ground and foliage to dry out before foraging molluscs come out at night.
Be vigilant during wet weather
After every bout of rain check and renew your slug and snail defences where necessary.
Encourage wildlife
Slugs and snails are a necessary part of a thriving ecosystem. Look after your allies in the war against them Image: Shutterstock
All of the animals listed below eat slugs and snails, so it makes sense to recruit them as your allies. Our wildlife gardening guides provide plenty of tips for encouraging them into your garden.
Hedgehogs
frogs
toads
newts
slowworms
birds
ground beetles
centipedes
shrews
mice
Avoid the plants most vulnerable to slugs and snails
Sluggish gardeners who don’t have the energy for a war against gastropods may prefer to avoid susceptible plants such as these delphiniums Image: Canva
If slug and snail warfare isn’t your thing, then don’t bother with the plants listed below :
Beans
Celery
Clematis
Dahlia
Delphinium
Doronicum
Gerbera
Helenium
Hollyhock
Hosta
Hyacinth
Lettuce
Lilies
Lupin
Pansy
Peas
Potato
Primula
Soloman’s Seal
Sweet peas
Tulips
Slugs and snails are here to stay!
Molluscs have been around for 500 million years, which has given them ample opportunity to perfect the art of annoying gardeners Image: Canva
There is no way of completely eradicating slugs and snails and if we could, our gardens would be in a terrible mess. Slugs and snails are primary consumers, munching through organic matter, fungi and algae and making it available to smaller organisms. Without them, we would literally be surrounded by rubbish. Think of them as one of nature’s dustmen, indiscriminate but efficient. They also form an important part of the garden eco-system, providing food for all sorts of animals. Concentrate your efforts on young seedlings and the most vulnerable plants, and accept that slugs and snails will always love your garden as much as you do!
Annelise Brilli is the Horticultural Copywriter for Thompson and Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.
Get out into gardens now and enjoy the spring performance of magnolias in full bloom Image: Magnolia ‘Red Lucky’ (Standard) from Thompson & Morgan
Cossetted within their velveteen coats, the buds of magnolia trees are just beginning to unfurl their voluptuous, vase-like blooms and wow crowds with a spectacular spring performance. If you’ve ever gasped in awe at a magnolia in full bloom but dismissed them as too difficult to grow yourself, then think again. Modern cultivars are increasingly versatile and reliable, with many being suitable for smaller gardens and even container growing.
Annelise Brilli is the Horticultural Copywriter for Thompson and Morgan. Annelise caught the gardening bug from her mother, whose tiny backyard was crammed with a huge collection of plants. As an adult, she had a career change into horticulture, gaining a training apprenticeship with the National Trust at Powis Castle Garden in Welshpool. She went on to work in a range of private and public gardens, later running a garden design and maintenance business. She is passionate about sustainable gardening and has developed her own wildlife-friendly garden which she has opened as part of Macmillan Coastal Garden Trail.
Recent Comments