Soldanella: Snowbell is one of the prettiest of the early spring alpines. In its native mountain home it can be seen blooming at the edge of the snowfields, hence the common name. Dainty bell-like flowers with deeply fringed margins droop gracefully from the tops of the upright flower-stalks. Lavender-blue is the usual colour but varieties in other shades are available. Soldanella needs some care, protection against winter is advisable and you will need to keep slugs away as they devour the flower buds in late winter or spring. Varieties: S. alpina (height four inches, spread nine inches, flowering period is March to April) has all the features of the genus, rounded leathery leaves and pale purple, fringed bells which appear in the spring. Unfortunately it is not free flowering; you will have more success with S. montana height six inches, spread twelve inches. The most floriferous and the easiest to grow is S. villosa (height six inches, spread twelve inches). It flowers later than the others (May to June) and is more robust. Site and Soil: Requires well-drained moist soil in light shade. Propagation: Divide clumps in summer.
Tanacetum: Tansy are generally grown for their silvery leaves rather than their white or yellow flowers. The blooms are button-like with only disc florets or distinctly Daisy-like with both disc and ray florets. Tanacetum must have good drainage; it does well in pots of compost outdoors. Varieties: T. densum amani is the one you are most likely to find in the catalogues, it may be listed as Chrysanthemum haradjani. Feathery silver-grey leaves which look like filigree form dense six inch high mounds. The summer flowers are small yellow buttons surrounded by grey woolly bracts. T. herderi is a nine-inch bush which bears silvery foliage and small heads of yellow flowers. Site and Soil: Requires well-drained open soil and full sun is essential. Propagation: Plant stem cuttings in early summer.
Thymus: Thyme can be useful in the rock garden as in the herb garden. There are two basic groups, the small bushy ones for planting in pockets between the stones and the carpeters which produce large mats of aromatic leaves and a covering of tiny flowers. These prostrate ones can be used to fill gaps between paving stones or as leafy blankets to clothe rocks. Cut back the stems in spring. Varieties: T. serphyllum is the basic carpeter, height one to three inches, spread two feet, flowering period is May to July. The small flowers are borne in round heads. Named varieties are grown albus (white), 'Annie Hall' (pale pink), coccineus (red), 'Goldstream' (mauve) etc. The basic bushy Thyme is T. citriodorus, height nine inches, spread twelve inches, flowering period is May to July with lemon-scented foliage and lavender flowers. There are excellent varieties and hybrids which are shorter and more compact, 'Aureus' (yellow leaves), 'Silver Queen' (silver/green leaves) and 'E B Anderson' (golden leaves) are examples. Site and Soil: Requires well-drained light soil in full sun. Propagation: Divide clumps in autumn or spring or plant stem cuttings in summer.
Trillium: Wood Lily is a beautiful plant for humus-rich soil and partial shade. It is a good plant for a large rockery. A thick underground rhizome produces several fleshy stems which bear the foliage and flower parts in threes. Three leaves, three petals, three sepals and three cells in the berry. The flowers which appear in spring are white, red, purple or more rarely yellow. Worth looking for, as it is eye-catching and long lived once established. Varieties: T. grandiflorum is the one you are most likely to find. It is also perhaps the easiest and the most attractive. The basic details are height twelve inches, spread twelve inches, and the flowering period is from April to June. The two to three inch wide blooms are white, turning pink with age. A double-flowered variety (flore pleno) is available. T. ovatum is rather similar but the leaves are dark green and mottled, and the flowers are reddish-purple. The yellow flowered Trillium is T. luteum (height eight inches). Site and Soil: Requires well-drained moist soil and thrives in light shade. Propagation: Divide clumps in autumn.
Tulipa: Species Tulip is suitable for the rockery as long as you choose the dwarf varieties. Bedding Tulips are lifted when flowering is over and the foliage has turned yellow but some Species Tulips are left in the ground over winter. Varieties: The list is enormous if you wish to be adventurous, but only tried and tested ones are included here. T. pulchella is a tiny four-inch dwarf, white, pink and violet varieties are available. T. tarda is another miniature, with several star-shaped white and yellow flowers on each stem. It blooms in April and May like most Tulips. For March flowers grow T. kaufmanniana (six to ten inches). This is the Water-lily Tulip which has many varieties. T. praestans 'Fusilier' (orange-red) has become popular, T. greigii (eight to twelve inches) with brown mottled foliage is an old favourite. Others to look for are T. clusiana, T. vyedenski, T. batalini and T. aucheriana. Site and Soil: Requires well-drained soil in full sun. Propagation: Remove bulblets when lifting clumps. Dry, store and replant in late autumn.
Vaccinium: is a large and commercially important genus, as it includes the Cranberry, Blueberry and Bilberry. They are all lime-hating shrubs, some are bushy and upright but many are low and spreading. There are a number of dwarfs, but you must choose with care. Vacciniums growing three feet or more are listed as rock garden plants in some of the books, the ones described below are ground-hugging prostrate plants or dwarf bushes. Varieties: V. vitis-idaea is the Cowberry, height six inches, spread eighteen inches, flowering period is May to June. The creeping stems and glossy oval leaves provide good ground cover. The small white or pink flowers are urn shaped and are followed by red berries. Several varieties such as 'Koralle', minus and compactum are available. V. praestans is another prostrate Vaccinium with white flowers and red edible berries, but it loses its leaves in winter. V. nummalaria is a twelve-inch high evergreen bush with pink flowers and black berries. Site and Soil: Requires well-drained acid soil in light shade. Propagation: Plant stem cuttings in late summer.
Verbascum: Rockery Mullein is generally associated with the herbaceous border, there you will find the three to six foot high varieties of V. hybridum. There are just three species which are small enough for the rock garden and they are worth growing in a sunny spot. Most of the basic family traits are leaves which are hairy or spiky, a profusion of bowl-shaped yellow blooms and a dislike of shade and heavy soil. Varieties: The rockery species which is closest in growth habit to the border Mulleins is V. dumulosum, height nine inches, spread twelve inches flowering period is July to August. The upright flowering spikes bear purple-eyed yellow flowers above the grey hairy leaves. V. spinosum is different, the leaves are tiny and spiny and the flowers are borne in loose clusters. The most popular one is a hybrid of these two species, V. 'Letitia'. It is a shrubby perennial which is covered by half inch yellow flowers from June to August. Site and Soil: Requires well-drained soil in full sun. Propagation: Plant root cuttings in later winter.
Veronica: Rockery Speedwell is a useful addition to the rock garden as it supplies midsummer colour and is easy to grow in a well-drained site. Several species are available and the popular ones are spreading plants which form a leafy mat. A word of caution some can become as invasive as Speedwells on the lawn, so pick a restrained one where choice plants are grown nearby. The rampant species include V. filiformis and V. prostrata. Varieties: V. prostrata (V. rupestris) is the most popular Rockery Speedwell, height four inches, spread eighteen inches or more and the flowering period is from May to August. Blue is the species flower colour, but there is white ('Alba'), pink ('Mrs Holt') and pale blue ('Spode Blue'). A good choice between paving stones but too invasive for a small rockery. V. pectinata provides non-aggressive ground cover, the pink variety 'Rosea' is the usual selection. Other Speedwells include V. fruticans (red-eyed blue flowers) and V. cinerea (grey foliage). Site and Soil: Requires well-drained soil and thrives best in full sun. Propagation: Divide clumps in spring.
Viola: Rockery Violet is an extensive genus and is instantly recognizable. For maximum display the familiar biennial Violas and Pansies are sometimes bedded out into planting pockets, but it is preferable to grow the perennial species. Two (V. odorata and V. cornuta) have long been associated with the herbaceous border, but the others described below are true Rockery Violets. Varieites: V. cornuta (horned Pansy) height six to nine inches, flowering period is May to August has many varieties, such as 'Alba' and 'Minor'. V. odorata (Sweet Violet) is earlier (March to May) and smaller (four to six inches high). For yellow flowers throughout the summer grow V. aetolica or V. biflora. For purplish-blue flowers and foliage choose the late spring flowering V. labradorica 'Purpurea'. Perhaps the easiest to grow is V. lutea and the smallest one you are likely to find is the mauve-coloured V. jooi. Varieties of V. gracilis are noted for their daintiness, look for 'Major' (yellow-eyed purple) and 'Moonlight' (yellow). Site and Soil: Requires well-drained soil in sun or light shade. Propagation: Plant stem cuttings in summer.
Zauschneria: Californian Fuchsia is a valuable plant for the rock garden as it produces bright flowers late in the year. Unfortunately this small shrub from N. America is not for everyone; it does need a warm and dry spot if it is to flourish. Abnormally cold winters are a killer, but it is well worth a trial if you have a sheltered spot. The flowers are tubular and red is the usual colour. Varieties: The only species you are likely to find is Z. californica, sometimes listed as Epilobium canum. The basic details are height twelve inches, spread eighteen inches and the flowering period is from August to October. Along the branched stems are grey hairy leaves and at each tip a cluster of one-inch long tubular flowers. It is deciduous. The species bears red blooms but several varieties are available with slightly different colours. 'Glasnevin' is orange-red and so is the hardiest one 'Dublin'. 'Solidarity Pink' is pink. Z. cana is a rare species with narrow leaves. Site and Soil: Requires well-drained soil in full sun. Propagation: Plant stem cuttings in summer.