Nasturtium lessons

October 11th, 2019 | Plant Talk with Graham Rice | 0 Comments

Nasturtium 'Bloody Mary'

This year has been the Year of The Nasturtium! We’ve had marigolds and sunflowers and cosmos, most annuals are going to get a turn, and next year it’s rudbeckia. But we learned something important from growing nasturtiums this year.

Well, I say we learned something… It’s more that we were reminded of two things that we knew all along: pests can destroy the display and the leaves tend to hide the flowers.

The best nasturtiums I ever grew were in pots, long ago, when we could buy an insecticide to mix into the compost and which was taken up by the roots. I never saw a blackfly or a caterpillar on my nasturtiums all summer. Now, like so many effective but harmful sprays, it’s no longer available – and quite right too. Organic treatments can be very effective, but you have to keep at it.

Also, at both the Mr F trials and at the display at the RHS Garden at Hyde Hall, the leaves overwhelmed the flowers. This happens when the stalks on the leaves grow longer than the stalks on the flowers, so the leaves are held higher.

In general, modern varieties tend to have shorter leaf stalks than older varieties so the flowers are more likely to be prominent. But the key is to avoid overfeeding, or any feeding at all! Never use Miracle-Gro or other general plant foods as it encourages too much growth. Next year I’m going to try old, exhausted potting compost without any nutrients and, if I feed my nasturtiums at all, I’m going to use tomato food which doesn’t encourage leafy growth.

Varieties? Try this year’s newcomer, ‘Bloody Mary’ (above), and any of the Tip Top Series – they all tend to hold the flowers above the leaves.

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Is one of our best known gardening writers. A graduate of the Royal Botanic Gardens, Kew, Graham was previously Gardening Correspondent of The Observer.
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