A-L of Rock and Alpine Plants
Natives of New Zealand, acaenas are vigorous, ground-covering plants with long, trailing branches covered in small leaves and, in some species, bearing wonderful, tiny burr-like. Look for A. buchananii, with its soft green foliage and brassy, little flowers. A. micvophylla, which is the most commonly seen species, has stunning bronze-grey foliage and red, bristle-headed flowers. Also look for ‘Copper Carpet’, which is especially colourful. ‘Blue Haze’ is another good sort and is available at most garden centres.
Native to dry hills in the Near and Far East, it makes tussocks of spiky leaves. It can take as much heat and drought as you can give it. A. glumaceum makes dark green clumps of foliage topped by shocking, bright pink flowers.
These are the miniature relatives of the common herbaceous border plant and, like their big sisters, they enjoy full sun and meagre, dry. The flowers appear in spring and early summer, but because the foliage is so attractive they are useful members of the rock garden all year round. A. ageratifolia has finely cut foliage and large flowers. A. clavennae has oval leaves that are a particularly luminous silver-grey. A. tomentosa has fernlike, soft grey leaves that form a ground-hugging mat covered with bright yellow flowers.
This is a lime-loving plant, but it will tolerate neutral or slightly acid soils for a warm, sunny spot. A. grandiflorum makes small shrubs bearing sprays of bright pink flowers all summer. Plants of the Pulchellum Group within the species are smaller with flowers in shades of pale to rose-pink. ‘Warley Rose’ is a popular cultivar.
Familiar to gardeners as A. mollis, the Lady’s Mantle; the dwarf form, A.alpina is worth having in the rock garden for its dainty leaves; the reverse sides glisten like silver setting off the sprays of small, yellow-green flowers. A. erythropoda is another widely available species also suitable for the rock garden; its small leaves are bronze-green in colour.
There are a number of species of this bulb, which are all relatives of onions and garlic. Allium caeruleum has bright blue flowers as does Allium cyaneum, which is slightly lower-growing. Allium karataviense has wonderful broad, grey leaves, tinged purple, and stubby flower stalks bearing pale, lavender-grey flowers.
Alyssum (now known as Aurinia)
Mat-forming plants that are a mass of flowers in the spring. However, after the big show they are not particularly interesting, so don’t put too much emphasis on Aurinia in your rock garden display. A. saxatile ‘Compacta’, ‘Dudley Nevill’ and ‘Dudley Nevill Variegated’ are all good, showy cultivars.
A. pyrethrum var. depressus is a fully hardy, ground-covering plant for a sunny place in a scree garden or gritty soil. The flower buds are a deep crimson opening to white flowers.
One of the finest blue flowers in the rock garden, A. caespitosa makes a tuft of stiff, narrow leaves forming a rosette around the flower cluster. It needs deep soil for its long tap root.
Andromeda polifolia ‘Alba’ and Andromeda polifolia ‘Compacta’ are both good evergreen shrubs for the rock garden. Their glossy, dark green leaves provide a perfect setting for the clusters of tiny white or, in the case of ‘Compacta’, pink flowers that appear in the spring. It needs an acid, moist soil.
All of the following plants are easy to grow, widely available and favourites in the rock garden for growing in gritty soil and in crevices. A. carnea makes a tuffet of narrow, dark green leaves around stems bearing tiny pink or white flowers. A. cylindrica grows best in crevices, where it will make a low rosette of grey-green leaves studded with clumps of pink or white flowers. A. lanuginosa makes trailing stems covered with silvery leaves and dainty, pink flowers. A. pyrenaica makes a pincushion of short, spiky green leaves, which in season are covered with single, white flowers. A. sempervivoides makes a rosette of smooth, flat leaves around short stems carrying small, pink flowers.
Here is a small shrublet for a hot, dry position. A. agardhii has silver foliage and gold-tinted flowers.
The small relatives of the Japanese windflower, A. japonica, are generally found on woodland edges and so appreciate cool, shaded positions in the rock garden. A. apcnnina grows from a tuberous rhizome and makes dainty, blue flowers. A. ranunculoides ‘Pleniflora’ has double, yellow flowers and it will work its way gradually through a rock garden on creeping, woody roots.
Easy to grow and quite showy, the evergreen, mat-forming A, caucasica “Rosabella” is covered in a mass of rich, pink flowers throughout spring and into early summer. ‘Snowcap’ is, as you would expect, a luxuriantly white-flowered cultivar. A. ferdinandi-coburgii ‘Variegata’ has insignificant flowers, but good green and white variegated foliage.
In the genus there is plenty of variety and a plant for most situations. A. balearica makes a tissue of pale green foliage covered with tiny, white star-like flowers; let it cover a rock in cool shade. A. purpurascens makes a mat of evergreen foliage and is covered in early spring with masses of shiny, pink stellar flowers; grow it in full sun. A. montana particularly likes cool crevices and will reward you with a waterfall of bright white flowers in spring.
Armeria juniperifolia (formerly known as A. caespitosa) makes an evergreen hummock of spiky leaves covered from late spring to early summer in bright pink flowers. Armeria maritima is best known as sea thrift, a seaside wild flower with pink flowers. ‘Vindictive’ has dark red flowers, or there is the white-flowered ‘Alba’. The foliage is grass-like and the flower stalks are like drumsticks.
Best known as the sun-loving denizens of the herb garden, the species suitable for rock gardens retain their pungent scent and silvery foliage. A. caucasica (once known as A. lanata) is valued for its great spreading mounds of silver, feathery foliage. A. schmidtiana ‘Nana’ makes rosette mats of finely cut grey leaves.
There are numerous named selections and clones of this common garden carpeting plant. Its sheets of flowers m shades of pink, mauve, purple, bright red and white are widely admired. It is only suitable for the largest rock garden or terrace, unless you keep its spread in check. Best in full sun and well-drained soil.
A cheerful introduction to summer, it grows easily in open, sunny places and most require only good. C. carpatica makes a lovely hum-mock of tiny bells in various shades of blue, mauve, purple and white. C. portenschlagiana, in spite of its name, is the easiest to grow, making a mat of bright blue. C. thyrsoides is totally different since the yellow flowers are held aloft on stiff stems. There are many others, too numerous to describe here.
These are my favourites for the rock garden (and the garden generally). They have excellent foliage, cheerful little flowers in white and many shades of pink and, best of all, spring-action seed pods. As the seed ripens, the flower stalk curls in tight against theand the moment the seed is perfectly ripe, it springs out, shooting the seed away from the mother, gradually colonising the area. C. coum flowers in winter and spring and the ‘Pewter Group’ are so-called for their heavily silvered foliage. The autumn-flowering C. hederifolium (formerly known as C. neapolitanum) is the one most commonly encountered and C. purpurascens flowers during the summer. They like well-drained, but moist soil with plenty of added humus, if necessary.
These shrubs are much loved for the intense perfume they possess and for the charming, waxy flowers that appear from late winter to early spring. D. blagayana is ground-covering. D. encorum makes a small evergreen bush. ‘Eximia’ makes trailing branches and D. mezereum is the one much used in old-fashioned cottage gardens. It is really rather tall for inclusion in the rock garden unless you keep it clipped back (by taking pieces for winter flower arrangements).
Dianthus x arvenensis, Dianthus gratianopolitanus and the stunning Dianthus deltoides are probably the best of the alpine pinks to begin with; all in shades of pink and white with mats of grey foliage and a clove-like perfume. They require sun and good drainage to do well.
Dryas octopetala makes an evergreen mat of dark green, leathery leaves, which sets off the yellow-centred white flowers to perfection. These plants appear from late spring through early summer and it is an easy little plant to grow in sun and well-drained soil.
The small-growing sorts of fleabanes offer some good candidates for both rock and scree gardens. Erigeron aureus has tiny, hairy leaves and bitty, yellow flowers. It dislikes any wetness, so is best on scree. Erigeron karvinskianus, also known as daisy-gone-crazy, deserves its common name since it quickly seeds itself in cracks, crevices and gravel, covering itself in a dusting of small, pinky-white daisies.
There are plenty of species to choose from in this long-flowering genus, but do look out for Erodium cheilanthifolilum and Erodium corsicum. Both have nice flowers and foliage, but do best in pots or pans, so they can over-winter in the alpine house.
Most alpine gardeners pride themselves on their collections of gentiana, they are the sine qua non of the rock garden, and are quite easy to grow as long as you pay attention to their pH requirements, which range from neutral to acid. They are best for a peat bed where they will also get the moisture they like. Gentiana sino-ornata demands nothing less than perfectly drained, totally lime-free soil to produce the fabulous blue flowers for which it is prized. ‘Inverleith’ is the most spectacular. Less fussy is Gentiana acaulis; the stemless, kingfisher-blue flowers rest on a mat of dark green leaves. The willow gentiana, Gentiana asclepiadea, makes long, whippy flower stems with blue or white flowers (G.a. Alba). Gentiana x macaulayi ‘Kingfisher’ is widely available and likes a good acid soil.
Of all the hardy geraniums, G. cinereum is probably one of the daintiest, making a spreading rosette of thumbnail-size leaves crowned in summer by masses of cup-shaped Flowers. It does well in full sun and in moisture-retentive soil. Look for the cultivar ‘Ballerina’, which has rosy-pink flowers with a wine-red web of veins spreading across the petals from the dark centre of each flower. The variey Geranium c. subcaulescens has similar characteristics but sports rich, magenta-tinted petals around an almost black central boss, which has a stunning effect.
Commonly known as rock, these plants are good for scree and rock gardens or for growing in walls or dry banks. ‘Ben Nevis’ has dark green foliage and bright orange flowers. ‘Jubilee’ has yellow blossoms and the species Helianthemum nummularium and Helianthemum oelandicum ssp. alpestre are evergreen shrubs, dwarf enough for a sink garden.
This is the genus that produces the dried flowers commonly known as Everlastings. For the rock garden, look for the species Helichrysum bellidioides, a carpet of grey-green leaves dusted over with papery white flowers. Helichrysum milfordiae makes a rosette of oval, woolly grey leaves and crimson buds that open to white flowers.
These plants like cool, moist soil that is rich in organic matter and also a position that offers partial shade. Hepatica nobilis makes a mound of soft, green leaves covered in spring with many simple white flowers. There are also pink, lilac and blue forms as well as a choice of double-flowered sorts. The garden variety Hepatica n. var. japonica is widely available and has dark, leathery, semi-evergreen leaves and lilac-blue flowers.
You often see St John’s wort grown as, but for the rock garden there are a few small-stature species available. Hypericum olympiaun makes a nice and tidy, little deciduous bush. It’s upright stems are covered in tiny, short green leaves and bear lovely, single, large egg-yolk yellow flowers that bristle at the their centres with long, silky stamens. It will seed itself, but not invasively. Another species to try is the lovely Hypericum empetrifolium ‘Prostratum’, which makes a low-spreading shrub with starry, yellow flowers. It can be tender so protect from frost.
If rock gardens had mascot plants, the edelweiss would unquestionably be it. L. alpimtm is widely available and much loved for its clusters of woolly, silvery-grey flowers and clumps of grey-green foliage. It does best in open sunny places.
Leucanthemum (now known as Rhodanthemum)
L. hosmariense is a favourite rock garden plant, loved by many for the shimmering mat of silvery leaves and masses of bright daisy flowers it makes all summer. When it is happy, as it usually is when given plenty of sun and well-drained soil, it can become overbearing, but responds well to vigorous thinning.
L. tweedyi and L. rediviva are two of the most popular species for rock gardens, making basal rosettes of thick leaves and branched stems carrying pale pink to rich pink flowers. There are many named hybrids as well offering a good range of colour. Lewisias prefer a lime-free soil and do best in cracks and crevices where perfect drainage is assured for their deep tap roots.
L. alpina, is an annual that will seed itself easily into nooks and crannies on the sunny side of the rock garden. It makes great whorls of grey, narrow leaves and racemes of tiny, snapdragon flowers in shades of purple and yellow.
L. flavum ‘Compactum’ is the species that makes what is probably the brightest yellow splash in midsummer. The flowers have a glossy radiance, which is complemented by the dark green foliage. It does well in any soil in the sun.
L. nummularia ‘Aurea’ is a freely-spreading, hardy perennial that will form mats of greenish-gold leaves, which are topped in summer by penny-sized yellow flowers — a real splash of sunshine in the rock garden. It likes a fair bit of moisture to do well and should be given a sunny spot as shade will encourage the leaves to go green. It can be invasive but can be kept in check by simply pulling up handfuls where it is not wanted.