This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
These climbers are among the most effective of all stove-plants when liberally treated, and are equally valuable either for exhibition purposes or for home decoration. At the Bath show of the Royal Horticultural Society this year, Mr W. Cole of Withington, Cheshire, exhibited a magnificent plant of D. amabilis, bearing about 120 trusses of its great wax-like flowers, the foliage being, according to a somewhat hackneyed expression, "as green as a leek," but in reality-much greener. It is needless to add that this plant created quite a furore, not only among amateurs, but also among professional plant-growers, who know a thing or two about these plants and their capabilities when well managed.
Dipladenias grow well in a fresh, open compost, composed of lumps of turfy or fibrous loam, leaf-mould, and coarse river-sand. The pots should be thoroughly well drained, and then the plants may be freely watered when making their growth. They are easily propagated from cuttings taken off soon after the plants break in the spring, and inserted in a well-drained cutting-pot, which should afterwards be plunged in a moderate bottom-heat and covered with a bell-glass, unless the convenience of a close propagating case is at hand. After the cuttings have rooted, pot them off carefully in the above compost, using small pots, and then set them in a close frame until well established, after which they may be removed either to the plant-stove, or to a shelf in the pinery where there is a stove-temperature, and a moderately humid atmosphere. As the pots become filled with roots pot them on, taking care not to allow them to suffer a check through being pot-bound, as this might induce premature flowering, and spoil the plants for the season.
When the pots become filled with roots, and the shoots 3 or 4 feet long, they will begin to show their flower-buds in the axils of the leaves; and at this stage a little clear manure-water made from sheep or cow dung, and a handful of guano thrown in, will greatly assist them in developing fine flowers, besides improving the colour of the foliage. In order to prevent the shoots from intertwining themselves in inextricable confusion, it is a good plan to train each growth on a separate piece of thick twine strained a few inches below the rafters, thinning out all weak or superfluous runners at the same time. When the flower-buds show themselves the twine can be cut, and the shoots carefully trained on a globe, or balloon-shaped trellis, ready for exhibition when the flowers expand. Two-year-old plants are most to be relied on for exhibition, as for the early summer shows the plants must be started into growth in December, or early in January, and grown on rapidly to the flowering stage; and young plants are more vigorous, and grow on more freely than debilitated old scrubby specimens, which persist in parting company with their lower leaves, and assuming a "leggy" appearance not to be desired either for exhibition or decorative purposes.
The plants are seldom troubled with insect pests if grown on freely in a humid atmosphere, but a slight dryness at the root often gives both thrip and red-spider an opportunity of commencing their ravages. The plants should be syringed at least twice a-day when growing; and if that is not sufficient to protect them from noxious insects, give an occasional syringing with. a decoction of Fowler's Insecticide - one of the best and cleanest we have used, and certain death to both black-thrip, red-spider, and greenfly. Two of the best Dipladenias commonly grown for exhibition are garden hybrids, having been raised from seed by Mr H. Luke, a well-known exhibitor at the Leeds and Yorkshire shows. These are D. amabilis and D. amoena, seedlings from D. crassinoda and D. splendens. Another, and if possible a more handsome variety, has been raised at Well Head, near Halifax, by Mr S. Fenwick - this being a seedling from D. amabilis named D. insignis, and now in the hands of Messrs Yeitch & Son, who have several times shown it in flower.
Its blooms individually measure nearly 5 inches in diameter, and are of a vivid rosy-crimson colour, and of good substance; while the plant appears to possess the robust constitution of its parent, and will doubtless make an effective plant for summer and autumn exhibitions when distributed among growers. The best kinds for exhibition are D. amabilis, D. splendens, D. crassinoda, D. amoena, and to these we may add the delicate white-flowered D. Boliviensis. This last species is very distinct in colour, all the other species bearing rosy or yellow flowers. A nice plant of this species was staged at the Bath show, but it is very rare in general collections, though very beautiful when well grown and laden with its snowy, salver-shaped blossoms. Dipladenias make effective stove-climbers trained up wires along with Cissus discolor, Gloriosa superba, G-. Plantii, or Stephanotis floribunda; and plants so treated produce a fine supply of choice flowers for cutting, and grouping along with Ferns and Lycopods in the drawing-room vase.
"When the plants are resting, they may be kept moderately moist at the root and in a dry and comparatively cool atmosphere. When they are wanted for starting, take them into the stove and plunge them into a moderate bottom-heat, repotting them in good fresh compost as soon as the roots begin to move. Do not give too much water at first, but let the plants get into vigorous growth, after which it may be liberally supplied - strengthened occasionally as already recommended. Some of the older species, as D. Harrisii, bearing golden-yellow flowers, blotched with crimson; D. flava, bearing clear yellow flowers; D. nobilis, bearing pale-rosy flowers; D. acuminata, and D. urophylla, - are more or less valuable as general decorative plants all requiring stove treatment, and most of them are very rare in modern gardens.
If our plant-growers were to pay more attention to the cross-breeding of these and other stove-plants, we should doubtless soon become possessed of other choice varieties, valuable either for decoration or public exhibition. F. W. B.