It’s biennial time again.
As our Aquilegias, Digitalis, Erysimums and Myosotis finish flowering, it is time once again to sow next year’s new ones to ensure that we get as good, if not better, display as this year.
This biennial cycle goes on in our gardens almost without us noticing it, as various plants self-seed in the quieter corners of our gardens. Plants such as forget-me-nots (Myosotis) can pop up almost anywhere if we leave the parent plants to seed in May and June. This happens in the wild as well, with plants such as hedge garlic/jack-by-the-hedge (Alliaria petiolata) seeding themselves at this time of year in the bottoms of farm hedges – the seeds then germinate before winter, surviving the harsh winter weather as young plants that then flower in spring/early summer. The parent plants die as they drop their seed.
So, what can you sow now that are grown as biennials? The starting point is to look for the letters HB at the beginning of the description of the plant. Sow Aquilegias cultivars now and watch out for a stunning display in May and early June – I like the look of ‘Green Apples’ and ‘Firecracker’ as interesting variations on the normal range of colours. Bellis ‘Pomponette Mixed’, although actually a perennial, is normally grown as a biennial and looks fabulous in the spring garden and in containers. It is loved by bees as well so we all win!
For something a little unusual, try Cabbage ‘Northern Lights Mixed’ with various foliage colours to delight you and your friends. If you leave them in until early summer they will flower and the yellow flowers are edible – yummy!! Dianthus barbatus, more commonly known as Sweet William, gives a stunning display in early to mid summer and there are a number of wonderful cultivars to choose from. Foxgloves (Digitalis) have come a long way in recent years from their biennial wild relatives and the range of colours and forms is worth studying, from ‘Excelsior Hybrids’ up to 1.5 metres to ‘Silver Cub’ at only 60cm high.
Pansies and Violas are amongst of the most popular winter and spring flowering plants for containers in our gardens and, although they are classified as perennials, we do tend to grow them as biennials. The flowers are edible as well as colourful and one of my all-time favourites is ‘Majestic Giants’ with flowers up to 10cm across. Wallflowers (Erysimums) are one of the more traditional biennial plants used by local authorities and larger public gardens for spectacular spring displays. Try ‘Tom Thumb Mixed’ for an easy to manage cultivar with a wide range of flower colours from yellows to rusts and reds. It works well in a container because it only reaches 20cm high.
Some plants can be nudged into a biennial life-cycle just by changing the sowing dates. Plants such as Calendula, Limnanthes and Nigella can be sown directly into the garden in late September, will germinate quickly in the warm soil and will then overwinter as young plants, flowering in April and May for instead of June, July and August. These plants are normally sold as hardy annuals for direct spring sowing. Give it a try and surprise yourself and your neighbours.
Whatever you grow now for your winter and spring garden, enjoy the surprises that these wonderful plants can give you.
I have worked in horticulture for the past 49 years and have become more involved with and concerned about the environmental impact that our profession has had on the world. I am married with 2 grown up children and 4 wonderful grandchildren. My first book, ‘The Yorkshire Organic Gardener’ was published in November 2018. I am Vice Chair of the Chartered Institute of Horticulture’s Young Horticulturist of the Year competition and am also the CIH Northern Branch Regional Organiser for the competition.
Recipient of 2021 RHS Harlow Carr medal for services to horticulture in the North of England.