Although purists may prefer to exclude ordinaryfrom rock gardens, their introduction certainly extends its season and provides colour into autumn. Since many of these recommended sorts are half-hardy , they will not go outside anyway until late May or June, when the spring flush of rock is waning.
or pheasant’s eye is a small hardy with finely cut and bright crimson like small . It grows 12 to 18 in. tall and needs to make an effect. A deep, rich, loamy soil suits it best.
Dwarf ageratums (Ageratum houstonianum) are low-growing (6 in.) hardy annuals with fluffy heads of mauve flowers like candy floss. They flower all summer and make good border edgings.
Brachycome iberidifolia is the swan river daisy, a slender-stemmed, half-hardyof 15 to 18 in. with many sweet-scented daisy flowers, 1 in. Across. The colours vary from white, pink and rose to . It is best grown in drifts in moist soil with sun.
Cotula barbata is the pincushion plant, a compact half-hardy annual of 4 to 6 in. with deeply cutspangled with golden flowers like daisies without the outer florets. It forms dense carpets of foliage, even in poor soil.
Dorotheanthus and Portulaca
Dorotheanthus bellidiformis (often sold as Mesembryanthemum criniflorum) makes dwarf mats of succulent linear foliage studded with vivid daisy flowers of cerise, crimson, buff, red, orange or apricot each more than 1 in. across. On a bright sunny day (the flowers close in dull weather) the effect is brilliant. Treat as a half-hardy annual oroutside in May for late flowers. Portulaca requires similar treatment and both do well in poor soil.
Portulaca grandiflora is the best species with round, succulentof 6 to 8 in. carrying cup-shaped flowers of white, deep rose, rose and white, crimson or clear yellow. There are also double varieties and the main flowering season is July and August.
Felicia bergeriana is the kingfisher daisy, a dwarf half-hardy annual of 4 to 5 in. with small but brilliant metallic-blue daisies which close in dull weather. Suitable for warm, sunny spots.
Cilia hybrida (Leptosiphon hybrids) can be grown between flagstones or in small pockets. It does not mind poor soil and only grows about 6 in. tall. It is a hardy annual with finely cut leaves and clusters of white, yellow, rose-pink, purple or violet flowers. All have yellow centres.
Gypsophila repens is a dainty hardy annual having cobwebby stems and tiny leaves. It is smothered in summer with dense sprays of dainty little white flowers. These look very pretty trailing over rocks or stone steps. There are also pink and red forms. The usual height is 12 to 18 in. Sowout of doors in autumn, or in cold districts in spring.
lberis umbellata is the best of the annual candytufts with racemes of white, four-petalled, sweetly scented flowers in character all through the summerand crimson forms are available and the normal height is around 12 to 15 in. Treat as hardy annuals and grow in light, well-drained soil in open situations.
lonopsidium acaule, the violet cress, can be sown directly on the rockery where it is to grow. In later seasons self-setusually maintain the stock. The violet-blue (sometimes white) flowers bloom from June to September on 2 to 3-in. Tufts of rounded leaves and stems. Hardy annual.
Layia elegans or tidytips has yellow, 2-in. Daisies with prominent white petal tips. These occur on 12-in, stems and persist for weeks. Well-drained soil and sunshine suit this hardy annual.
Linaria maroccana is a charming hardy annual with slender 10 to 18-in, stems packed with small, snapdragon-like flowers. Normally these are violet with white blotches but white, mauve, crimson and yellow forms occur. The plants need full sun and well-drained soil and should be grouped for maximum effect. They also make good pot plants.
Among the smaller annuals no plant is more adaptable than Lobelia erinus, a charming, compact, half-hardy annual with smooth serrated leaves and pale blue, white-throated flowers. These bloom continuously all summer and may be grown in hanging baskets,and borders as well as in the rock garden. Selected forms, which come true from , include the deep blue, white-eyed Bluestone; white Snowball; deep carmine-red and white-eyed Rosamund, and Mrs Clibran which is brilliant blue with white eyes. The usual height is 6 in. but there are also pendulous lobelias with lax, 18-in, trailing stems, much used in hanging baskets. L. tenuior is a good blue for pot work.
strumosa is grown as a half-hardy annual. Ideal for bedding in sunny annual borders, the plants also do well in rich, slightly acid soil in rock gardens. The stems grow 9 to 12 in. tall with bunches of bright flowers in scarlet, orange, crimson, carmine, pink, purple, cream, white or yellow. The race known as Suttonii is particularly fine.
Nierembergia caerulea (N. hippomanica)is a perennial usually treated as a half-hardy annual, although plants are occasionally lifted in autumn and over-wintered under glass. It blooms all summer, the 6 to 9-in, stems spangled with cup-shaped flowers of lavender with yellow throats. It needs sun and shelter in moist but well-drained soil.
Phlox drummondii does best in deep moist soil and should be treated as a half-hardy annual. The lightly scented flowers come in clusters and persist all summer in vivid shades of scarlet, violet, pink, white and yellow. There are large-flowered hybrids around 12 in. and dwarfs of 6 in. A warm sunnyis preferred.
caeruleum is a lovely little annual with masses of pale blue starry flowers and needle-fine leaves on 2 to 3-in. Stems. Sow the seed in rock pockets out of doors in April.
Silene coeli-rosa, also known and sold under the names Lychnis coeli-rosa and Viscaria oculata, is a vivid, easy-to-grow annual which should be sown where it is to flower in March or April. Sometimes called rose of Heaven, it has slender, 18-in. Stems with narrow leaves and many rosy-red, white-centred flowers about 1 in. across.