‘What do I do with this?’ my friend asked as we stood looking at his rose garden, a miserable, dull collection of stunted bushes, edged by stones. ‘Rip it out!’ I said, ‘and build a rock garden!’
And so we did. We re-laid the stones to create little planting bays, refurbished the soil with gritty compost, planted with alpine plants and top-dressed with gravel. The result gave pleasure throughout the year, as there is always something of interest in a rock garden.
Rock gardens can hold so much variety in a small space because the plants are all dwarf or compact forms. Structure for winter interest is created with tiny conifers such as Juniperus communis ‘Compressa’, which will never grow large. If you have ericaceous soil, the tiny-leaved Rhododendron impeditum and Pieris ‘Little Heath’ will give green leaves all year in addition to their flowers. Other miniature trees can add to the structure: Salix x boydii with soft, grey-green leaves gives catkins in spring, Acer palmatum ‘Red Pygmy’ looks glorious in summer and Sorbus reducta bears big heads of pink fruit on its short branched stems.
Once the structure is in, the fun starts. Choose little alpine plants to fill each bay. If you have lots of space then Phlox, campanulas and geraniums can cover the ground – but make sure to choose alpine forms, not large herbaceous kinds. Some Dianthus can give wonderful scent, dwarf Aster alpinus will flower for ages and plants such as Chiastophyllum oppositifolium will drape gracefully over a rock edge. Some plants will give you a double show. Pulsatillas have beautiful hanging heads of flowers in early summer and then later on they are magnificent, with their soft, fluffy seed heads blowing in the wind.
Then for the icing on the cake – the bulbs. Because these take up little floor space – they will pop up, flower, then their leaves will shrivel away – you can have them in addition to the dwarf plants. Start with snowdrops and crocuses, but one of the loveliest in spring is the pale blue Scilla mischtschenkoana ‘Tubergeniana’. Follow these with dwarf Narcissus such as ‘Baby Moon’ and dainty tulips such as Tulipa humilis. Bulbs are not just for spring. In autumn, Colchicum pusillum – one of the naked ladies, as they flower without any leaves – or the brilliant sunshine-yellow Sternbergia lutea mean that the colour just keeps going. There is even a snowdrop that comes out in October, Galanthus reginae-olgae, so there are always surprises.
If you want a really contemporary look make a crevice garden. This is made from thin pieces of rock standing on edge, very close together. It can be free standing or in a raised bed or a large trough. I like thin pieces of natural stone, split down the strata of the rock, but broken paving slabs or slates or tiles can be used as well – whatever will merge best with the style of your garden. A crevice garden needs really small plants, tucked into the cracks between the slices of rock and then topped with gravel or little chips of stone. Androsace, saxifrages, gentians, Silene, Sempervivum and Sedum will all do well – and you can tuck lots of plants into the crevices.
Even if you only have a balcony you can still have a rock garden. Troughs and old sinks are ideal, but you can have fun with any container that has good drainage. I have seen old loos, cans, worn-out boots and rope pots all transformed by the rosettes of sempervivums or saxifrages growing round a few pieces of stone. A friend living in a camper van was jealous of our rock garden – so I built him one in the glove compartment of his van; everyone can have a rock garden!
A sunny open position is best for a rock garden – but if you have a shady damp place you will need to choose different plants such as baby hostas, ferns and little primulas.
Don’t just plonk rocks on heaps of soil. Set the stones in so they slope back slightly so the rain drains back into the border.
Don’t plant too deep. Leave the plants proud by 3 cm so you can top-dress with gravel. This suppresses the weeds and conserves moisture.