Iris Pumila and Iris Stylosa.—We mention two out of the many beautiful Irises suitable for a rockery. Try to get the variety of Pumila called Cœrulea, a lovely sky-blue. Stylosa is the scented Iris that flowers in winter. It likes sun and shelter, and dry, hard ground. It must be manured.
Lithospermum Prostratum.—If we were only allowed one rock plant out of all there are, we would choose this one. It flowers nearly all the year round in some parts of England, and its blue is as vivid as the blue of a Gentian. If you can plant it so that its roots can tuck themselves under a big rock as they grow, so much the better. We have transplanted a big plant of it successfully, but we did it in fear and trembling, as it is said to hate disturbance. You had better not try to divide it. It can only be increased by cuttings, and they are not at all easy to strike.
Phlox Setacea.—This is one of several varieties of dwarf Phloxes that are useful for edgings and rockeries. They must have sun and well-drained soil, or they damp off.
Speedwell: Veronica Repens.—There are many varieties and sizes of Veronica. Some make big garden shrubs. The one we recommend here is a tiny trailing plant, with small pale blue flowers. It increases at a great rate, and is easily divided. Slugs like it, but do not make headway against it in many gardens. It makes a pretty dwarf edging amongst stones, as it creeps amongst them, and partly covers them.
“THE ROAD TO ROME.”
The Sedums, Saxifrages, and House-leeks, or Sempervivums, are all suitable for rockeries. Some kinds of Sedums, or Stonecrops, grow wild in our hedges. You should get Sedum Spectabile, the Japanese Stonecrop, which bears large heads of pink flowers in August. There are many widely differing varieties of Saxifrage, or Rockfoil; for instance, Muscoides, the Mossy Saxifrage, makes a plump, low cushion of green moss on your rockery; Sarmentosa is the well-known weed, Mother of Thousands; Umbrosa is London Pride. Some have large leaves and pink flowers; some send up pyramids of white flowers from tufts of silvery leaves. You must grow one or two at a time, and get to know them by degrees. Sempervivums are those little green rosettes you see spreading in clumps on old roofs and walls. One of the most fascinating is Sempervivum Arachnoideum, the Cobweb House-leek. It covers itself with a curious white down that looks like a spider’s web. They like a dry sandy part of the rock garden, and full exposure to the sun.
Besides these plants, you should put a few bulbs in your rockery. Some of the very small Daffodils, Narcissus Minimus or Bulbocodium look charming coming up through a mossy carpet of Arenaria Balearica, for instance. You could also have some Snowdrops, some Siberian Squills, some autumn Crocuses, some Fritillaries, and some Dog’s Tooth Violets (Erythronium Dens Canis). We much prefer the English names for flowers, but it is often necessary to give both, so that you should recognize it in the catalogues. We heard of someone who sent to the other end of England for a plant advertised as Tussilago Fragrans, or the Winter Heliotrope, and she was much disappointed to receive a bit of the common Coltsfoot, that was an obnoxious weed in her own garden. Someone else sent for Hieracium Aurantiacum, which certainly sounds a first-class name; but she did not want a bit of the orange Hawkweed, as it had established itself more firmly than she wished in her rock garden already, and had to be kept in bounds with a spade.
We have not given you separate lists for a sunny and a shady rock garden, because we shall tell you a little in another chapter about plants that like shade. You must have some Primroses, Polyanthuses, and Auriculas on your rockery, and though they like the sun in spring, the more delicate kinds need some shelter from the hot summer sun. Try to get Primula rosea, the hardy rose-coloured Himalayan Primrose, and Primula Cashmeriana, a Primrose that sends up heads of mauve flowers on a fat stalk. Both need much moisture. Then, the Japanese Primroses are very handsome, and seed themselves when once established; and Sieboldi, with its many varieties, is easily increased, either by seed sown in spring or by division of the roots.
Now we have chosen just a few flowers for your rock garden, and with every word we write others come and look at us reproachfully, saying, ‘Why are we left out?’ We see neat little tufts of Thrift, or Sea-pink, and hanging sheets of white-flowered Cerastium, Anemones of sorts, Alpine Violas, Forget-me-nots, Hepaticas, Gentians, the finer Columbines, and shrubs of various kinds and sizes. But we have only had one aim in writing this chapter, and that was to lead you just one step towards the rock garden you must make for yourself when you are older. Then you must get yourself ‘Wall and Water Gardens,’ by Gertrude Jekyll, and ‘My Rock Garden,’ by Reginald Farrar, two books that will teach you all that books can about this most fascinating side of garden craft. But from the first one we should like to quote a short passage that tells you how a wise gardener supplements what he learns from books by his own qualities of patience and observation.