Diary one – Sweet pea: the ‘root’ of success

As we gardeners know, there are many correct ways to do almost everything.  However, whether experienced or amateur, we are guilty of carrying on unquestioningly, just because that’s how we’ve always done it. We all get into habits over the years, but it often pays to question why we blindly follow the gardening advice passed down through the generations.

I hope that by reading the reports of my technical trials you will gain some helpful tips and alternative ways of growing some of the exciting varieties we offer at Thompson & Morgan.

Diary One – Sweet pea: the ‘root’ of success

Diary One – Sweet pea: The ‘Root’ of Success

Sweet pea seedlings in the Root Trainer

With the best will in the world, transplanting seedlings can be difficult to carry out in a prudent manner without damaging the delicate root system. How do we know how well our precious seedlings will cope with the unnatural movement from their nursery haven into the final container?

At the trials site I was interested in how the home gardener can overcome this problem. The best solution is to buy pre-germinated sweet pea plugs with a strong tap root. Of course you may pay a premium for such a quality plant, but would the higher price mean in terms of overall plant quality?

The trial was pretty simple and has produced some staggering results to date.


Sweet pea ‘Sweet Dreams’, selected for its outstanding fragrance, exhibition standard blooms and superb growing performance, was sown in a standard 40mm cell tray and again in our  Root Trainer plug.

Four weeks after germination plugs were potted on to their final position. Containers with a 36cm diameter and a support structure were used. Five plants of each plug type were planted into two separate pots using a good compost and general fertiliser. The plants were maintained in a sunny position and controlled water and feeding regimes were used to ensure an unbiased trial across the two pots.


Just two weeks after sowing it was clear that the extra space and form of the Root Trainer had resulted in a more vigorous root system. The seedlings were fuller and the roots double the length (plant on left).

All images in this report show a fair comparison of root trainer against standard plug. Both plug formats were sown on the same day and kept in the same environment throughout the trial.

Diary One – Sweet pea: The ‘Root’ of Success

Root comparison – Root Trainer on the left, standard plug on the right

The Root Trainer could be easily opened up for me to check on the development, great for the less patient gardener amongst us! It was clear to see by week 4 that the sweet pea’s natural tap root structure had benefited from the extra leg room of the Root Trainer plug!

Diary One – Sweet pea: The ‘Root’ of Success

Comparison of root lengths

With such overwhelming results, I was keen to get the plants into their final pots and continue to record the height and bloom count as the weeks continued.

11 weeks after germination…

Although both plugs grew away successfully the Root Trainer clearly provided the best start (shown below).  The Root Trainer format reigned supremely over the standard plug. An obvious difference in overall habit, with several more stems which held the sweetly scented flowers. The height at week 11 was 110cm, twice the height of the standard 40mm plug.

Diary One – Sweet pea: The ‘Root’ of Success

19th June – standard plug (left), Root Trainer (right)

Diary One – Sweet pea: The ‘Root’ of Success

19th June – standard plug (left), Root Trainer (right)


Bloom count up to  1 July 2013

Sweet pea ‘Sweet Dreams’ – height: 1.8m (6’), spread: 30cm (12”). Supplied cell-raised with an average of 5 sweet pea plants per cell. Pinched and ready for planting straight out.






Diary One – Sweet pea: The ‘Root’ of Success

The results after 11 weeks


Wishing you a bountiful summer, happy gardening!

Pin It on Pinterest