One of the most exquisite and interesting rock-plants I have ever seen is clematis davidiana, a plant only introduced of recent years, but noticeable wherever seen; it is not a climber, as its name might lead one to suppose, for it only grows two feet high, and generally trails along the ground; the flowers are curious in shape, and of a metallic blue-grey colour; the foliage is very neat and pretty; it blooms about July, and should be planted so that it can be examined closely.
The fumitories are elegant plants, and nearly always in flower; the blossoms are small, yellow, sometimes white, and borne in profusion amongst the finely-cut foliage, which, the whole summer through, is a bright clear green. With one plant of corydalis lutea a stock can soon be obtained, as this variety seeds freely. All the fumitories prefer a light soil and a sunny position.
Dwarf evergreen shrubs greatly improve the appearance of the rockery in late autumn and winter, especially when they add berries to their attractions. The cotoneasters are evergreen, and when about a foot high are very suitable for such a position. C. horizontalis and C. micicrophylla bear scarlet berries, and are altogether very choice; they must not be allowed to get too large, but taken up when little over a foot high, and others substituted for them.
Various bulbs, which we generally plant in the border, find a prettier background in the rockery; here each bulb is made the most of, and, where very small, is seen to greater advantage; even if ever so insignificant, it cannot get buried away under a spadeful of soil, nor get splashed with mud. You must often have noticed how crocuses get blown over and spoilt by the wind, but in a cosy nook of the rock-work, planted fairly close together, and in a “pocket” surrounded by bricks, they find a happy home, and can be inspected without any difficulty. Personally, I do not care for crocuses in a line; one cannot see their pure transparency, and only get an idea of a broad band of colour; close at hand, their dewy chalices, exquisitely veined and streaked, seem far more beautiful, particularly where the finer sorts are selected. All crocuses do not flower in spring; some of the prettiest species bloom in autumn, though many people, seeing them at that time, imagine they are colchicums; the latter, though certainly very decorative when in flower, are followed by such coarse leaves that the crocus is decidedly preferable.
The hardy cyclamen are very suitable for a rockery, as, being beauties in miniature, they are apt to get lost in a mixed border. C. neapolitanum has marbled foliage and pretty pink flowers, and C. europeum (maroonish crimson) is also well worth growing; they must be placed in a shady part, yet where the drainage is perfect; stagnant moisture kills them.
The hardy orchids should be tried too, especially the cypripedium; it is not generally known how handsome some of them are; they like shade and moisture; indeed, through the summer the peat they are growing in should be a regular swamp, or they will fail to produce fine flowers.
Another plant that likes peat is the little daphne eneorum. This is an evergreen, and produces its pink fragrant flowers every spring; it will not do in very smoky places, but, like the heath, must have a fairly pure atmosphere.
The alpine pinks are treasures for the rockery, and do well in town gardens; they flower nearly all the summer, and are not particular as to soil and position, though they prefer plenty of sun.
The gentians look very well on rockwork, but like a stronger soil than most alpines, loam suiting them best. Water should be generously given during spring and summer. G. acaulis is the best for amateurs.
The red shades found in the geum tribe are very uncommon, being neither crimson, scarlet, nor orange, but a mixture of all three, with a dash of brown thrown in. They flower continuously, and have dull green woolly foliage, which sets the flowers off well. They need a light, well-drained soil. Geum chilense, or coccineum plenum, is a good kind, and so is G. miniatum; both are about two feet high, but require no staking whatever. Of course, it will be understood that sticks, except of the lightest kind, are quite inadmissible on a rockery.