Plantsman’s favourites Hans Kramer, co-owner of the highly respected Dutch nursery De Hessenhof, selects his favourite plants for May
There’s a wealth of plants that look good in May, but how to pick the best? Hans Kramer selects his favourites
Crambe grandiflora
This rarely grown Caucasian species is the perfect mix between the tall C. cordifolia and the low C. maritima. I can never understand why such a good plant is found only in the wild. At the end of May the first flowers start to open and you can smell the unmistakable scent of rapeseed, although this is sweeter. The inflorescence is a wide multi-branched umbel with hundreds of white flowers, bigger than in C. cordifolia, with soft yellow centres. Seed is easily set and sometimes it germinates en masse in spring. Height 1.2m. Growing conditions Good fertile soil, preferably alkaline. A sunny spot. Hardiness RHS H7. Origin Caucasus. Season of interest Late spring.
Delphinium trolliifolium
I’ve tried many delphiniums, but none grow as easily as this one. It’s the first delphinium to flower here and most years the brilliant, deep-blue purple flowers start to appear at the end of April. They bloom in widely spaced inflorescences and the large, shiny, deeply incised leaves provide a good backdrop. The plant likes to grow informally between shrubs or other spring plants, such as wood anemones, where it will seed around, so don’t be too tidy. By August everything is gone and the claw-like tubers stay safe in the ground until next year. Height 60cm. Growing conditions Humus-rich soil, dry in summer is no problem. Part shade. Hardiness RHS H7. Origin American pacific northwest. Season of interest Late spring.
Polystichum setiferum Green Lace (= ‘Gracillimum’)
An American visitor to our nursery once described this magnificent fern as ‘dynamite’, and he was right. The fronds of this rare cultivar, a selected seedling of ‘Pulcherrimum Bevis’, are extremely fine, almost thread-like, and yet they remain green throughout winter. Old plants can grow to almost one metre across, but this will take years. You can’t propagate from spores or bulbils – the only way is by division. But once you have it, you can be sure you’ll have it for your whole lifetime. Height 70cm. Growing conditions Not too dry, alkaline is no problem. Part shade to full shade. Hardiness RHS H7. Origin Europe. Season of interest Year round.