Planting a rainbow

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They look a bit like small foxgloves, but penstemons have a lot more going for them, particularly colour.

Not for them just purple or perhaps white; no, these perennials have played long and hard in the artist’s palette and the result is anything from pure white through pinks and blues to aubergine. Which goes a long way to explaining why penstemons are such big favourites.

They are vigorous, mostly frost-hardy and come in both evergreen and semi-evergreen forms, and their abundance of bell-shaped flowers make for an eye-catching display in July to August. And bees adore them for their plentiful supply of nectar.

They are at their best in herbaceous borders but there’s nothing to stop anyone from growing them where the sun shines and the soil is fertile and well-drained.

Even heavy clay can be persuaded to house them – just incorporate plenty of well-rotted material and add a few handfuls of coarse grit to encourage decent drainage.

The best way to make sure penstemons keep flowering is to dead-head regularly, and it’s equally important to prune them annually to stop them from growing woody and lank.

In early May, when the worst of winter has, hopefully, gone, trim them back. When new shoots appear at the base, remove the old flower spikes and take a few cuttings because there is one major problem with penstemons – they have a bad habit of disappearing. One year they flower wonderfully; the next, there is no sign of them. So, a few cuttings in reserve can be used to fill the gap.

In autumn, cut back established plants by about a third, leaving some foliage to provide protection from ice and snow.

To give plants the best start to a new growing season apply a balanced, general-purpose fertiliser in spring and then add a hefty mulch because penstemons are greedy feeders.

There are numerous named varieties on offer – if your preference is for red, then take a look at ‘Chester Scarlet’; ‘Alice Hindley’ produces lilac-blue blooms; ‘Burgundy’ has, not surprisingly, intense burgundy blooms. And if you want something a little more delicate, then ‘Apple Blossom’ has lovely white-throated pink flowers.

The majority of plants grow to 18in in height, although some will top 24in, and ‘Burgundy’ and a few others can better even that.