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.
The Clianthus is one of the most showy and most suitable plants for training up the rafter or for covering the back wall of the conservatory - especially if planted out in a suitably prepared border. The flowers, which hang down in drooping racemes, are seen to much better advantage when trained up a rafter. They are naturally of straggling habit, and more suitable for training up the roof than for pot-culture : still, with due care and attention, very good plants can be grown in pots, and when well done makes a very good exhibition plant. There are three varieties of Clianthus in general cultivation - Clianthus Dam-pieri, C. magniflcum, and C. puniceum. By far the most showy of the three is C. Dampieri - in fact it is one of the most gorgeous of our cool greenhouse plants. The flowers are of a bright orange-scarlet, with a large black blotch in the centre of each flower. It is generally considered a very difficult plant to grow well; indeed it is but very rarely seen in flower at all, being very much subject to the attacks of red-spider, and liable to damp off suddenly in its earlier stages of growth. C. magnificum is almost hardy, and in many places would do very well trained against a south wall, provided a little protection was given it during winter.
In many parts of Ireland it stands without any protection whatever; and we have seen plants of it against a wall with stems as thick as a man's arm, and they flowered most profusely every year.
The soil best adapted for the cultivation of the Clianthus consists of good fibry loam and peat in equal parts, with a goodish sprinkling of silver sand. The pots should be well drained, as they require plenty of water when growing, and the syringe should be applied pretty frequently to keep red-spider in check; but the best antidote for spider is to keep the plants in vigorous health. The Clianthus roots readily from cuttings, which should be of the half-ripened wood, and put in under a bell-glass, and the pot plunged in a mild bottom-heat. The young plants should be grown on as quickly as possible - especially in the case of C. Dampieri. After they are established in their pots, a cool pit or frame will suit them well. They should be kept moderately close, and slightly shaded from bright sunshine, and syringed every evening during the summer. The aim should be to get the foundation of good plants made during the first year, rather than the production of flowers; they should therefore be pinched frequently in order to induce them to break into many shoots. They may be wintered in a house or pit where the temperature ranges about 45°, and the amount of water given during the winter should not be in excess of the demand for it.
After growth begins in the spring, they may be shifted into larger pots, or planted out if intended for that mode of culture. In forming the bed, care should be taken to secure good drainage, and the soil should be used in a rough state : some charcoal may be added, which will help to keep the soil sweet. Their season of flowering is from the end of May onwards, and they are certain to be very much admired when in flower.