M-Z of Rock Plants and Alpines
A real miniature, M. monanthos makes a prostrate creeping tuffet of green, studded with dainty, yellowin late spring. However, this only happens if it has the exceedingly sharp that it likes best, so plant in sandy .
For a long flowering period, the mat-forming N. repens is hard to better. It is not altogether hardy, so plant in sheltered spots or give the underground, creeping roots some winter mulch protection and it will repay you with masses of brilliant white flowers.
The gentian blue flowers on dark, wiry stems make O. cappadocica very desirable in the rock garden. It likes moisture and part shade to do well. O. verna has paler blue flowers and larger foliage.
Ononis fruticosa is a deciduous shrub that looks like a bristle brush because of its finely divided, hairy leaves. It carries its bold clumps of lavender-pink on flowers during summer and likes good drainage in a sunny position. Gravel mulching.
O. dictamnus is commonly known as Cretan dittany and was a favourite windowsill plant in old cottages. ‘Kent Beauty’ makes a prostrate plant and is covered during summer in the characteristic fragrant, oval leaves of the oreganos. The flowers are quite showy with papery pink bracts like the flounces of a tulle ballgown. It is not hardy, so best grown in a pot to over-winter in the alpine house. O. rotundifolium is a hardy little shrub which has showy, green bracts disguising the pale pink flowers, which cover the shrub throughout the summer.
The species O. adenophylla makes clumps of grey-green clover leaves and lipstick-pink flowers in early spring; it also increases easily from the tiny bulblets that form around the base of the mother bulb. Another good species worth trying is O. enneaphylla, also known as scurvy grass. It makes wonderful silvery-grey leaves and pearly-pink flowers. Both species do best in full sun and need good drainage.
Papaver alpinum is a delicate little thing, short-lived but free-seeding. It makes a clump of grey leaves over which the papery, white flowers flutter on wiry stems. Papaver miyabeanum has a similar habit and lifespan, but their flowers are faded yellow.
These are perennial favourites in the, but there are a few species that qualify for the rock garden. Penstemon hirsutus ‘Pygmaeus’ is a hardy evergreen and makes a compact little plant; bearing characteristic tubular white flowers, tinted lilac-blue on the outer surface of the petals. P. pinifolius is larger growing and has pillar-box red flowers. P. newberryi f. humilior is a hardy, evergreen shrub that makes a mat of dark green painted over with rose-pink flowers in summer. All like good drainage and sun.
Phlox caespitosa is a hardy evergreen that makes a neat mound of spiky, green leaves covered with mauve or white flowers during summer; it is good for the rock garden or alpine sink garden. Phlox nivalis ‘Camla’ is a popular evergreen that makes mounds of wiry stems carrying masses of cherry-pink flowers in early summer; this one likes rich, moist soil to do well. Phlox douglasii ‘Crackerjack’ is also evergreen and the leaves all but disappear beneath the blanket of magenta-pink flowers in early summer. Clip over phlox after flowering to keep a neat shape.
P. vaccinifolium has a curious beauty with wiry, red stems holding aloft bright pink flower spikes above a neat carpet of evergreen foliage. The show begins in late summer at a time when the rock garden can be a little dull. So it is valuable for that reason as well.
The species suitable for the rock garden are mostly mat-forming perennials and flowers carried on long, arching stems. Potentilla alba has white flowers. Potentilla aurea has yellow. The hybrid, Potentilla tonguei, has peach-coloured flowers and Potentilla megalantha makes a mat of silver foliage with pink flowers nestling among the leaves.
The great herald of spring in the garden, primulas have something to offer the alpine house with the graceful Primula allionii and its numerous cultivars. It makes a mound of grey foliage smothered in flowers. Give it excellent drainage in a crevice and rich gritty soil and it won’t let you down. Primula auricula, Primula hirsuta, Primula marginata and Primula minima are just a few of the many species that can be grown in the rock garden or alpine house.
The pasque flower, Pulsatilla vulgaris, is widely available and there are quite a few cultivars to choose from when making a rock garden. Give them a good alkaline soil and full sun, and they will perform well.
Some of the most interesting alpine and rock plants are found in this buttercup clan. Ranunculus. alpestris is the alpine buttercup and the bright white, cup-shaped flowers are held above the glossy, dark green leaves for a long season; from late spring to mid-summer. Ranunculus ficaria albus is a mat-forming perennial with similar glossy leaves and glossy, white flowers. Both these like moist soil and partial shade. Ranunculus calandrinioides is happier in sharply drained soil and sun; it has long, grey-green leaves and saucer-shaped, white flowers on long stems. Ranunculus montanus ‘Molten Gold’ has rich yellow flowers and dark green leaves all with the characteristic buttercup gloss.
While most alpine and rock plants are grown for their flowers, this genus is valued for the curiously tinted foliage of species like R. australis, R. a. Lutescens Group, R. hookeri, which come in varying shades of silvery-grey, and R. haastii, which makes a carpet of green in spring and gradually darkens to dark brown by winter. Please note that they need good drainage to keep their feet out of winter wet and gritty soil in sun or part shade.
A bulbous perennial that likes a sandy, acid soil and a sunny spot, but plenty of moisture during summer to do well. Not a hundred per cent hardy, so plant in a sheltered spot. R. baurii is the most popular species, although R. deflexa offers a wide choice of cultivars, like ‘Douglas’ with cardinal red flowers.
There are some real curiosities among the willows, and a few of them are suitable shrubs for rock gardens. I fell for the weirdness of ‘Boydii’ with its gnarled, stubby stems and little, round, felted, grey leaves, but still have to find a place for it where the upright habit won’t be too startling. Salix apoda is prostrate and in spring male plants carry chubby catkins, like fat woolly caterpillars. Salix herbacea barely lifts itself off the ground and is studded with acid-green catkins in spring. Salix lindleyana also hugs the ground and has pink-tinted catkins. One of the prettiest of the prostrate willow tribe is Salix reticulata, whose springtime flush of catkins is followed by the attractive, deeply veined, oval leaves cloaking the ground-hugging branches. They need moist soil and a place in the sun or part shade
Commonly known as bloodroot, this perennial creeps along by its rhizomatous roots, making clumps of grey-green leaves that complement the show of glistening, white flowers that often have a curious violet-blue or pink tinge on their reverse. It is hardy but needs moist, humus-rich soil and shade.
As for saxifragas, so for sedums. There are dozens to choose from and each as charming as the last. They like sun, but otherwise will tolerate even the most depressing soil conditions. Give them some care and they will reward you with an exhilarating variety of foliage and form; from the tiny, silvery-grey pebbles of Sedum spathulifolium to the long, flat tapering leaves, variegated pink and cream, of Sedum kamtschaticum ‘Variegatum’. Again, turn to a specialist nursery for advice on which to choose.
Once again, a plethora of riches. Sempervivums are diverse and beautiful, love to be sunbaked and will tolerate the poorest soils. Sempervivum tectorum, the common houseleek, is a clump-forming rosette of succulent leaves that colonises the thatch and pantiles of old cottages. Look out for the lovely S. arachnoideum, called the cobweb houseleek. For the film of fine, white filaments knitted across the leaves. S. montanum makes rosettes, soft blue-green in colour and S. giuseppi has small, hairy rosettes that knit together to form a tight mat. Take advice from the specialists when choosing.
Another large genus, but not overwhelming like the previous three. Sisyrinchiums have iris-like leaves, which shelter the demure flowers that are coloured shades of blue and violet; although there is a very desirable straw-coloured cultivar called ‘Quaint and Queer’. S. I dahoense ‘Album’ has starry, white flowers for most of the summer and S. macounii has charming violet-blue flowers. They all need well-drained soil and a place in the sun.
A favourite denizen of the herb garden and often recommended to edge paths and grow betweenstones. Some of the creeping thymes deserve to be in the rock garden, but there are so many to choose from. My favourite carpeter of all is the woolly thyme, T. pseudolanuginosus, and the variegated ‘Doone Valley’ makes a wonderful, neat mound of gold-variegated leaves. A good herb specialist will offer the widest choice. Full sun and dry conditions are needed.
Veronica prostrata offers a wide range of cultivars in varying shades of white. Blue, violet and pink. Veronica pectinata has trailing stems of violet-blue flowers and Veronica filiformis is one to watch out for because it is annoyingly invasive. Veronicas are very easy to please in any soil and sun.
With a dry position in the sun, this curious plant will reward you with cascades of tubular, scarlet-red flowers. It is not entirely hardy so make sure there is some shelter for the plant. Zauschneria californica ‘Dublin’ is one of the more flamboyant species.