Dig It – April Tips from the Secret Gardener

Rockery

You might not associate a garden rockery with butterflies and moths but actually the hot and dry microhabitat, with well-drained soil, can offer conditions suitable for some great nectar plants. The rocks can also provide butterflies with warm places to bask in the sun. 

Garden butterflies that have been spotted so far this year, and are in need of nectar, include Small Tortoiseshell, Peacock, Red Admiral, Comma, Brimstone and the Small, Large and Green-veined Whites. There are also plenty of garden moths starting to appear – in the daytime Humming-bird Hawk-moth could be seen. At night, the following could come to light: March Moth, Dotted Border, Hebrew Character, Common Quaker and Herald. 

If you have a sunny rockery then there are many plants, such as alpines, that you could add to provide a source of nectar over the next few months. The following suggestions all like well-drained soil in full sun and are available in garden centres now.  

Common Rock-rose Helianthemum nummularium

This is a low-growing, evergreen shrub, with saucer-shaped, yellow flowers from June to September that likes sunny chalk grassland, cliffs and rocks. Its sun-loving nature is reflected in the name Helianthemum, which is from the Greek helios meaning sun and anthemon meaning flower, as the flowers open in sunlight.

In the wild it can be a foodplant for caterpillars of the Brown Argus, Northern Brown Argus, Silver-studded Blue and Green Hairstreak butterflies and for moth caterpillars such as the Wood Tiger and Annulet. 

Many garden cultivars have been developed from this native plant, with flowers ranging from white through yellow to deep red. Examples include Helianthemum ‘The Bride’ which has a profusion of pure white, yellow-centred, flowers on vigorous, evergreen, silver-grey carpeting mounds. Helianthemum ‘Wisley Pink’ has pale pink, orange centred flowers from late spring to mid-summer.

Rosy-flowered Rock-cress Arabis blepharophylla ‘Spring Charm’

Scented, large, glowing pink flowers occur from early to late spring, above mat-forming rosettes of dark green foliage. Having the Royal Horticultural Society’s Award of Garden Merit indicates that this variety is worth growing in your garden. It is in the cabbage family, which is loved by white butterflies - the native Hairy Rock-cress Arabis hirsuta can be used as a foodplant by Orange-tip butterfly caterpillars. 

Perennial Candytuft Iberis sempervirens 

This is also in the cabbage family and has masses of pure white flower heads from mid-spring to early summer, on an evergreen bushlet of 30cm height. 

Border Carnation Dianthus caryophyllus ‘Sunflor Vivre’ or ‘Sunflor Charmy’

Stunning pink flowers on 15cm stems, over evergreen foliage, create an eye-catching display throughout the summer. 

Thyme Thymus spp. 

These herbs, with aromatic leaves, form an evergreen cushion with pink flowers.

Thymus Worfield Gardens has variegated leaves with red new growth and is 10cm-high. Pink flowers occur from late spring to mid-summer. 

Other nectar plants for rockeries include Aubretia Aubrieta spp., Saxifrage Saxifraga kabashiana, Cowslip Primula veris, Thrift Ameria maritima and Mexican fleabane Erigeron karvinskianus. 

Although the plants like well-drained soil they will need to be watered well before planting and until established. Remember to deadhead to prolong flowering and there should be a lovely show of blooms over the next few months for you and the butterflies.

 

Happy Gardening! 

The Secret Gardener