This section is from the book "Beautiful Gardens - How To Make Them And Maintain Them", by Walter P. Wright. Also available from Amazon: Beautiful Gardens: How To Make And Maintain Them.
The following notes on a selection of the best rock plants may be interesting: -
Acaena microphylla. - A tiny evergreen, flowers green with red spines, summer.
Acanthohmon glumaceum (Prickly Thrift). - Rosy flowers in summer, likes a sandy compost.
Aethionema grandiflorum. - Rosy flowers in summer, grows 15 to 18 in. high, likes a sandy soil.
Alyssum. - Saxatile compactum, yellow, spring; and varie-gatum, with variegated leaves, are inexpensive and useful plants. Compactum can be raised in quantity from seed. Montanum, yellow, spring; and Olympicum, yellow, summer, are less known.
Androsaces. - Beautiful little flowers. Carnea, rose, July; Chamaejasme, pink, spring; lanuginosa, rose, summer; and villosa, rose, spring, are all gems. Bits of limestone should be stuck amongst the plants.
Anemones. - See special chapter.
Antennarias. - Tomentosa, with leaves covered with silvery down, is a well-known carpeter. Dioica, pink, early summer, is not so well known, but is very pretty.
Aquilegias (Columbines). - Favourites alike for borders and rockwork. Alpina, blue, white centre; caerulea, blue, and the various hybrids of it; glandulosa, blue, tipped white; Pyrenaica, lilac; and Stuarti, blue and white, are amongst the best of these charming flowers.
Arabis (Rock Cress). - There is little between Alpina and albida; both are cheap white carpeters, flowering in spring. The double form is quite distinct, and a valuable plant. Lucida, white, and its variegated variety are also good Arabises.
Arenaria Balearica (Sandwort). - White, spring and summer, creeping habit.
Armeria cephalotes (Thrift or Sea Pink). - A beautiful plant, either for rockwork or edgings, crimson flowers in autumn, compact, neat growth.
Asperula odorata (Woodruff). - White, sweet, flowering in spring, habit dwarf.
Asters (Michaelmas Daisies). - One or two of the dwarfer species, such as Alpinus, purple, summer, may be used; but most of the Michaelmas Daisies are better in the border.
Aubrietias. - Useful companions for Arabises. The varieties of deltoidea, such as Campbelli, violet; Leichtlinii, rose; and Fire King, bright red, are among the best.
Campanulas. - The dwarf species provide us with many beautiful rock plants, notably Alpina, dark blue, summer; Carpatica, blue, and its white variety, summer; fragilis, lilac purple, summer; Garganica, blue, summer; iso-phylla, lilac, summer, trailing; Raineri, blue, summer; and rotundifolia, blue, summer.
Fig. Campanula Raineri.
Cerastium Biebersteinii is a silvery-leaved carpeter.
Cyclamen. - The hardy species Coum, rosy red, spring; Europaeum, bright red, late summer; and hederaefolium, (Ivy-leaved) of different colours, spring, are valuable for rockeries and banks. They thrive in shade.
Cypripediums (Lady's Slippers), - -These beautiful hardy Orchids do best with shade, and in a peaty compost; a sandy bank does not suit them. Spectabile, rose and white; and Calceolus, yellow and red, summer, are two of the prettiest.
Dianthus (Pinks). - The value of this genus was pointed out in Chapter VII. Alpestris, red, early summer; Alpinus, dark rose, early summer; arenarius, white, spring; caesius (Cheddar Pink), rose, spring; cruentus, blood red, summer; deltoides (Maiden Pink), rose, summer; glacialis, red, early summer; neglectus, rose, summer; and superbus, rose, summer, are all worth including.
Dodecatheons (American Cowslips). - Meadia, white or lilac, spring; and its varieties elegans, frigidum, and giganteum are desirable things. They like a moist place.
Draba (Whitlow Grass). - Aizoon, yellow, spring, should be grown.
Dryas (Mountain Avens). - The creeping evergreen octopetala, white, late spring, may be grown, and should have peat in a cool spot.
Erigeron (Fleabane). - The dwarf species Roylei, purplish blue, summer, may have a place.
Erinus Alpinus, violet, spring, is a useful plant.
Erodium (Heron's Bill). - Two species are suitable, namely macradenium, violet, summer; and Reichardi, white, summer.
Erythroniums (Dog's Tooth Violets). - Charming flowers of spring. Americanum, yellow; Dens Canis, deep rose; grandiflorum, pale yellow; and giganteum, white, are good.
Gentiana (Gentian). - These give us the rich blues which are so comparatively uncommon. Acaulis, spring; Andrewsi, summer; Bavarica, summer; and verna, spring; are four of the best of these valuable flowers.
Geranium (Crane's Bill). - Several of these are excellent, and as they spread rapidly they soon cover a good deal of space. Cinereum, grey leaves and light red flowers; argenteum, silvery leaves and light red flowers, summer; and Lancastriense, rose, early summer, are three of the best of the dwarf species.
Gypsophila repens, creeping, flowers white and light rose, summer, is serviceable.
Helianthemums (Sun Roses). - The varieties of vulgare are the most suitable. They will grow almost anywhere, and flower profusely.
Hutchinsia Alpina, white, spring, is a pretty Alpine, and does well in sandy soil.
Iberis (Perennial Candytuft). - These pretty flowers are extremely useful, as they establish themselves in most soils, and flower profusely. Corifolia, white, spring; Gibralta rica, white, suffused with pink, early spring; and semper-virens, white, late spring, are all good.
Irises. - The dwarfer, sun-loving forms should be represented, particularly cristata, blue and yellow, spring; biflora, purple, spring; pumila, lilac purple, spring; and reticulata, violet and yellow. See also special chapter.
Leontopodium Alpinum (Edelweiss). - Although the time has long passed since this plant had any special interest it may be grown by those who admire its white, woolly foliage.
Linaria Alpina (Toad Flax), violet blue, summer and early autumn, is a neat Alpine.
Linnaea borealis is an interesting evergreen, with flesh-coloured flowers in spring.
Linum (Flax). - The bright flowers of these useful plants make them very welcome. Alpinum, blue, spring; arboreum, yellow, spring; Narbonense, blue, late spring and early summer; and perenne, pale blue, early summer, are all pretty.
Lithospermum prostratum (Gromwell), a trailing sub-shrub, bright blue, summer, is a valuable plant. It enjoys sandy soil.
Macrotomia (Arnebia) echioides, yellow, spring.
Myosotis alpestris (Forget-me-not), blue, summer, is worth including.
Narcissi. - The smaller forms, such as Bulbocodium (Hoop Petticoat); cyclamineus, Johnstoni Queen of Spain, juncifolius, minor, and triandrus (Angel's Tears) should be included. They look charming on rockwork.
Nierembergia rivularis, white, July, trailing, may be chosen for a damp, shady place.
Omphalodes verna, blue with white throat, spring, is a dainty little creeper that will grow almost anywhere.
Onosma Tauricum (Golden Drop) is a charming yellow summer flower that thrives in sandy soil.
Oxalis (Wood Sorrel). - Both Bowiei, rose, summer; and floribunda (rosea), rose, spring, are good.
Papaver (Poppy). - Alpinum, yellow, summer; and nudicaule, orange, with its yellow and white forms, summer, should be grown.
Phlox. - See special chapter for a selection of dwarf forms.
Primula (Primrose). - Several species are indispensable for the rockery. Cortusoides, rose, early summer; denticulata, lilac, late spring; formosa, lilac, yellow eye; Japonica, crimson; and other coloured forms, late spring, like a cool, moist spot, and peat. Marginata, violet, spring; rosea, rose, late spring, likes a cool spot; Scotica, purple, yellow eye, late spring; and viscosa, rosy purple with white eye, summer, are a few of the most valuable species. The varieties of Alpine Auricula, Cowslip, Polyanthus, and Primrose must not be forgotten. They are particularly good in cool spots, and luxuriate in damp soils.
Pyrola rotundifolia (Winter-Green), white, sweet, summer, is worth growing.
Ranunculus (Crowfoot). - Several species are good for the rock garden, and aconitifolius, white, spring, and amplexicaulis, white, spring, are two of the best.
Saponaria ocymoides (Soapwort). - A pretty, pink, summer-flowering trailer.
Saxifraga (Rockfoil). - One of the most important genera for the particular purpose we have in view, and one which comprises a considerable range of forms. The following should certainly be included. Aizoon, cream, late spring; ceratophylla, white, spring; cordifolia pyramidalis, red, spring; cotyledon pyramidalis, white, early summer; granulata, white, spring; hypnoides, white, late spring and early summer; longifolia, white, summer; oppositifolia major, purple, spring; and Wallacei (Camposi), white, spring. A classification of the genus, and a description of all the best forms, will be found in "Cassell's Dictionary of Practical Gardening," Vol. II.
Sedum (Stonecrop). - There are many species in this genus, and among them may be named as suitable for rockwork, acre, yellow; album, white; glaucum (Hispanicum), pink; lydium, pink; pulchellum, rosy purple; rupestrum, yellow; and Sieboldii, pink.
Sempervivum (House Leek). - This also is a large genus. A small selection may include arachnoideum (Cobweb House Leek), red; and Tectorum, red.
Silene (Catchfly). - Acaulis, pink, summer, and its varieties alba, white, and rubra, red; alpestris, white, early summer; maritima, white, summer; and Virginica, crimson, summer, are a few of the best of this genus.
Soldanella Alpina, violet, spring, is a pretty plant.
Sweet Peas, Cupid, various colours, summer.
Fig. Cupid Sweet Peas on a rock bank in the author's garden. Although often a failure, they flowered splendidly here.
Thymus lanuginosus (Woolly Thyme) is useful.
Triteleia uniflora, lilac, spring, is a bulbous plant which does well in warm soils.
Tropaeolum polyphyllum, yellow, early summer, is a trailer that may be pressed into service.
Veronica (Speedwell). - Several species of this large genus are available, notably Chamaedrys, blue, spring; saxatilis, blue, summer; Teucrium, blue, summer; and T. dubia (prostrata or rupestris), blue, summer.
Waldsteinia trifolia, yellow, spring.