A bare stone path or terrace can look very austere, but most have a few crevices and cracks that can accommodate low-growing plants that aren’t trip hazards. While a small niche may look unattractive to use, the paving provides a cool and damp area that's often perfect for small alpines, or sun-loving and compact herbs.
The most important thing is the aspect. If it’s sunny, most of the plants in the open are likely to have silvery or aromatic foliage. If it’s shady though, it won’t be suitable for silvers, and it will be a struggle to find things to grow there. If it's very shady try ferns and ivies, but seek expert advice form Fibrex Nurseries - www.fibrex.co.uk.
When planting, buy small young plants and gently strip off most of the compost and squeeze them carefully into the crack, in a position where footfall isn’t going to crush them. Give them a water, top dress with grit, and then let them get on with it on the basis that some will and some won’t. This is easiest to do in March and April and there are plenty of inexpensive alpines on sale then.
Suitable plants for crevices
1. Dianthus squarrosus
Many small pinks can be accommodated in a crevice, or crack. This Russian dianthus has mats of blue-grey leaves and scented single white flowers.
2. Androsace sarmentosa 'Sherriffii'
Strong and easy with rosettes topped with pink flowers in April and May.
3. Aubrieta deltoidea
This garden favourite does well in walls and in crevices, although it does need a yearly shearing after flowering to keep it tidy. There are pink, red and purple forms.
4. Arenaria alvacariensis
This forms a green dome of tight foliage, with small white flowers in late spring. Easy and hardy.
5. Thymus serphyllum
Lots of thymes make good crevice plants and there are many named form of this species. Go for smaller-leaved forms with dark foliage and pick flowers, because these show up well. However ‘Silver Posie’ (a variegated pale-pink thyme) and lemon thyme (Thymus citriodorus) could also be used.
6. Helianthemum nummularia
Rock roses can also thrive in paving, but the greyer-leaved ones are softer-stemmed and more prostrate. 'Wisley Primrose' and 'Cornish Cream' are both excellent. Cut back after flowering.
7. Saxifraga 'Southside Seedling'
An easy saxifrage with sprays white flowers, each petal marked in dark red. Put it somewhere away from feet as the flowers can reach 30 cm (12 in).
8. Erigeron karvinskianus
This tiny little daisy will self-seed once planted and, in dry gardens, the flowers will develop crimson tints. Packets of seeds can be sprinkled in crevices.
9. Valerian - Centranthus lecoqii
Valerian will and does self-seed, but this Moroccan valerian is a soft lilac-pink and not as aggressive as others. It's fully hardy, but only suitable for out-of-the-way places because it’s tall. (up to 1m)
10. Alchemilla mollis
The lime-green froth looks good in early summer, but do tidy it well after flowering - unless you want it to self-seed a lot.
11. Dierama pulcherrimum
The tall angel’s fishing rod loves to self-seed in a moist crack, although it can reach a metre in height so you may have to manage it and position it. Put its feet in the shade.