Campanula: Bellflower is an important genus of alpines and offers something for everyone. Amongst the many dwarf types there are difficult tender species which are a challenge even for the experts and there are popular ones which are both easy and reliable in the open garden. All need well-drained soil and the addition of lime if the ground is acid. June and July are the peak flowering months, and the Campanulas have a well-earned reputation for bearing masses of blooms. Praised in all of the books, there are still a number of limitations. Colours are almost entirely restricted to white and blue, and the young foliage is especially susceptible to slug damage in spring. In addition, a few species can be invasive and a threat to surrounding plants. Varieties: There are two distinct flower types, depending on the species. The usual form is a bell, sometimes held erect but more commonly pendant. The other form is a star-like bloom. C. carpatica is the most popular Campanula, height nine inches, spread twelve inches, flowering period is June to September. It bears cup-shaped bells, two inches across, in shades ranging from pure white to deep blue. C. cochlearifolia (Fairy Thimbles) is a much daintier plant, it spreads as wide as C. carpatica and flowers during the same period, but it forms a ground covering mat and the three inch high flower stalks bear small pendant bells in blue or white. If the site is shady you can grow C. muralis (C. portenschiagiana), height four inches with a spread of twelve inches. But do remember that it is a rampant grower producing purple bells on trailing stems. Another vigorous species is the starry C. poscharskyana, if you want a starry flowered Campanula which will not spread everywhere then choose C. garganica which produces compact tufts with blue or white flowers. C. zoysii with its urn shaped flowers is an example of a hard to grow Campanula. Site and Soil: Any well-drained, non-acid soil and thrives in sun or light shade. Propagation: Sow seeds or divide clumps in spring.

Cassiope: has wiry stems with small bell like flowers requiring moist, cool and lime free conditions. It is easy to see that Cassiope belongs to the Heather family, and it is easy to spot the difference. With these plants the leaves are scale-like and clasp the stem, giving a whipcord appearance. The white or pink blooms appear in late spring or early summer. The buds are damaged by frost so choose a sheltered spot. Varieties: The easiest one to grow is C. lycopodioides, a prostrate mat forming species which grows only two to three inches high but spreads eighteen inches or more. The cord like stems are clothed with tiny quarter inch flowers, each one white with a red calyx. Another easy one is the erect hybrid C. 'Edinburgh', a free flowering plant with white edged leaves and white flowers. One of the parents of this hybrid is C. tetragona, the tallest of the rockery Cassiopes with clusters of quarter inch pink tinged white bells on the twelve inch high stems in April and May. Site and Soil: Humus rich acid soil is required, thrives in light shade. Propagation: Plant stem cuttings in summer.

Cerastium: Snow-in-summer is a popular rock garden plant. Only a small minority of alpine nursery catalogues list it and the books which mention it issue a stern warning. The silvery-leaved sheets, which bear white flowers in early summer, will soon spread like a weed and choke out other plants. This is true and Cerastium has no place in an average sized rockery, but there is little to beat it for quickly covering a large dry bank. Varieties: The ordinary Cerastium is C. tomentosum, height four inches, spread twenty-four inches or more, flowering period is May to July. The white flowers (one inch across) have notched petals and are borne is loose clusters above the woolly oblong leaves. The dwarf variety C. tomentosum columnae is equally rampant. The only restrained variety is C. alpinum lanatum, a compact grey-leaved Cerastium which forms neat mats, but it needs protection against winter rain and is not really worth the trouble. Site and Soil: Any well-drained soil, thrives best in full sun. Propagation: Sow seeds or divide clumps in spring.

Chamaecyparis: False Cypress is one of the most popular conifers in Britain. Several types are just too quick growing for the rock garden, don't be tempted to plant C. lawsoniana 'Allumii', 'Columnaris' or 'Fletcherii' because it looks small and attractive in the garden centre. There are, however a number of dwarfs which are highly recommended for the rock garden. Leaves are scale-like and the branchlets form flattened sprays. The cones are small and round. Varieties: C. obtusa has several good rockery varieties, 'Nana' (round, dark green), 'Nana Gracilis' (round, shell-shaped sprays of branchlets, dark green) and 'Nana Lutea' (round, yellow). C. lawsoniana also has a number of slow growing varieties, 'Ellwood's Gold' (columnar, yellow-tipped green), 'Minima Aurea' (conical, yellow) and 'Minima Glauca' (round, green). Finally there are several varieties of C. pisifera, the popular and feathery 'Boulevard' (conical, silvery-blue) and 'Plumosa Compacta' (round, blue-green). Site and Soil: Well-drained acid soil, thrives best in full sun. Propagation: Plant stem cuttings in autumn.

Corydalis: is ferny and delicate and each tubular bloom is spurred at the rear and lipped at the front. Some are fibrous-rooted; the rest arise from tubers. There is no basic colour, one species is bright blue, some are yellow and others are white or pink. One species will spread and flower everywhere but another one may fail to flower even in expert hands. Varieties: Pride of place must go to the much praised C. cashmeriana with clusters of pure blue flowers, height six inches, spread six inches, flowering period is April to June. There is a problem, it is difficult and needs peaty, well-drained and cool soil. C. lutea is much easier to grow, the flowers are just ordinary yellow but they appear from March to October. Others include C. wilsonii (blue foliage, yellow flowers and C. solida (rose, purple or white flowers). Site and Soil: Requires well-drained open soil and thrives in sun or partial shade. Propagation: Divide clumps in spring.

Cotoneaster: has a favourite garden variety and that is C. horizontalis a spreading three foot high bush grown against house walls or between taller shrubs. This one has no place in the average rock garden, but there are several dwarf Cotoneasters which are useful for clothing rocks or bare patches of soil. These ground-hugging types have small white flowers in summer followed by an abundance of showy berries and rich foliage colours in autumn. All are hardy and are tough enough to grow anywhere. Varieites: C. congestus nanus is a fine evergreen, less than one foot high with blue-green foliage and red berries. C. adpressus is even more prostrate, a deciduous species with Holly-like berries amongst the bronzy red leaves in autumn. C. dammeri is perhaps the best of the lot; it grows only a few inches high but spreads up to seven feet. The oval leaves are glossy and the bright red berries are borne singly or in pairs. The variety of C. microphyllus to choose is thymifolius. Site and Soil: Any garden soil, thrives in sun or light shade. Propagation: Plant cuttings in late summer.

Crocus: and hybrids can be grown in the rock garden. Goblet-shaped flowers appear in many colours bronze, white and blue as well as the familiar purple or yellow. Several types are described below, and the ones recommended for the rockery are not the large flowered Crocuses seen everywhere in spring. Varieties: There are three basic groups. The favourite ones for the rock garden are the Winter Flowering species, planted in September and blooming in February. All are small, three to four inches high, and include C. imperati (striped white and purple), C. susianus (the Cloth of Gold Crocus with bronze and golden petals) and C. chrysanthus with its host of hybrids. The Spring Flowering Dutch hybrids grow about five inches high and bloom in March and April. Scores of varieties are available in a wide range of colours. The Autumn Flowering species blooming between August and October offer a much more restricted choice. C. speciosus varieties are the most popular; producing attractive flowers in white, lilac or purple. Site and Soil: Any well-drained soil in sun or light shade. Propagation: Divide overcrowded clumps in autumn.

Cyananthus: Trailing Bellflower is a low growing alpine which appears in most text books but it is hard to find in the catalogues and garden centres. It should be better known, as it is an excellent choice if there is a damp but well-drained spot to fill and if you live in a cool district. The prostrate matted stems bear solitary flowers at their tips. Cyananthus is closely related to Campanula, but it usually bears funnel-shaped blooms with wide-open lobes rather than bells or stars. Slugs can be a problem. Varieties: C. microphyllus is the one most likely to survive the winter. Basic details are height three inches, spread twelve inches, flowering period August to September. The clear blue flowers are tubular with five narrow petal lobes spreading about one inch across. White and dark blue varieties are available. C. lobatus is also quite reliable, it is taller than the previous species and the flowers bear wide petal lobes. The usual colour is bright blue. C. sherriffii needs to be kept indoors. Site and Soil: Requires well-drained, humus rich soil, thrives in light shade. Propagation: Sow seeds in spring or plant stem cuttings in late spring.

Cyclamen: is generally thought of as a pot plant large, long-stemmed flowers with swept-back petals. If this flower form appeals to you there are hardy dwarfs with one-inch flowers to grow outdoors. The foliage is often marbled with silver and the blooms are sometimes fragrant. Buy growing plants rather than dried corms. Varieties: There are winter, spring, summer and autumn flowering Cyclamens, the four varieties described below will provide blooms almost all year round. C. hederifolium (C. neapolitanum) is the easiest and most popular, the ivy-shaped marbled leaves appear after the first flowers have opened. The flowering time is September to November for flowers to follow in January to March grow C. coum (round leaves, flowers white, pink or red). Plant C. repandum (purple twisted petals) for blooms in April and May. C. purpurascens provides the July to September blooms. Site and Soil: Well-drained, humus rich soil in partial shade is required. Propagation: Sow seeds in summer, plants cannot be divided.

Cytisus: Broom bears whippy stems with tiny leaves which are almost completely clothed with Pea-like flowers in either spring or summer, depending on the variety. They are easy plants to grow; thriving in dry and starved soils, but Cytisus cannot tolerate root disturbance, so buy pot grown plants and do not try to transplant established specimens. Yellow is the usual flower colour but there are one or two whites, pinks and reds. Varieties: Choose a dwarf species. Even here you must be careful, some of the so-called dwarfs such as C. kewensis (spreading, April flowering) and C. beanii (upright, May flowering) can reach two feet. For the average sized rock garden there are C. decumbens (six inches high, prostrate, bright yellow flowers in May and June), C. ardoinii (eight inches high, arching golden yellow flowers in April and May) or the larger C. purpureus (eighteen inches high, semi-prostrate, lilac flowers in May). The baby Broom is C. demissus (three inches.) Site and Soil: Thrives best in poor, sandy soil in full sun. Propagation: Sow seeds or plant cuttings in summer.

Daphne: is a wonderful plant and the dwarf varieties are always praised by experts. The sight and fragrance of a well-grown specimen in full flower is lovely. But it is not trouble free, some species are hard to grow and all are difficult to propagate. They can be short lived and all parts are poisonous. Still, the starry flowers borne in profusion in the spring easily outweigh the drawbacks. Varieties: There is a small group of easy dwarf Daphnes and beginners should pick one of them. The most popular and perhaps the best is D. cneorum attaining a height of six inches and a spread of six feet, flowering period is April to May. The sweet smelling pink flowers may cover the whole shrub, recommended varieties include 'Eximia', Variegata' and pygmaea. Another excellent six-inch high species is the pink flowered D. arbuscula (April to June). D. retusa is rather different, it grows about eighteen inches high and the flowers which appear in April and May are white or purple. D. neapolitana can reach two feet or more. Site and Soil: Well-drained, humus-rich soil is required, thrives best in full sun. Propagation: Plant stem cuttings in summer.