Some plants like cool conditions, with the winter temperature ranging between 45° and 50°F (7°- 10°C). These plants will not enjoy higher temperatures, although many of those in the next group, needing a temperature of 55°-60°F (13-16°C) will survive a winter either with lower or higher temperatures, without any ill effects. Plants that thrive in cool conditions will not necessarily like to be warm in winter, so choose other plants for your warm rooms.
The most notable cool-growing plants are the various ivies, the Tradescantias, Eucalyptus,, and Araucaria excelsa.
Both H. hibernica and H. canariensis areand do best if they are trained up a stake or on trellis work. There are two forms of H. canariensis generally available, of which the most popular is the one with variegated , with a wide silver margin and a dark green centre. The other, ‘Golden Leaf’ has bright glossy green with a yellowish patch in the centre. Although from the Canary Islands, these plants are quite hardy out of doors, They do not make their best impression until they are quite large.
On the other hand many of the forms of the common ivy are satisfactory as small plants. They can be divided into two main sections, those that are self-branching and tend to make erect little bushy plants and those that are either trailers or climbers. The latter either have to be trained up some support or put in a hanging, which may well look effective, but is a nuisance to water. The self-branching ivies will branch without any stopping, while the trailing forms require to be stopped in order to produce sideshoots and will only do this if they are quite sizeable plants; smaller plants will just replace the original growing points and then grow on.
Among the self-branching ivies are ‘Pittsburgh’, ‘Chicago’, ‘Minima’, `Minigreen% and ‘Green Ripple’, with plain green leaves, while among those variegated with silver are the ‘Variegated Chicago’, ‘Little Diamond’, `Heisse’, and `Goldchild’, which is more cream than silver. Among the trailers some good plants are ‘Glacier’, ‘Eva’ (sometimes called ‘Little Eva’), and `Maculata’. An unusual plant is ‘Golden Jubilee’, also known as `Goldheare’. This has the centre of thea deep yellow and a dark green margin. Unlike the other ivies it needs is much light as possible and has the disconcerting habit of making a lot of new without any leaves; however patience is all that is required as eventually the leaves form. The other ivies will grow happily in quite shaded conditions, although the variegated forms look better in well-lit situations. During the winter you may get some unvariegated leaves coming at the end of the branches. These should be removed at the beginning of March. should be kept on the dry side at all times.
The so-called German ivy is in reality a climbing groundsel (macroglossus variegata). It has roughly triangular leaves of dark green and cream and is one of the few house plants that do not require spongeing, as the leaves are covered with a waxy secretion. It is a vigorous climber that will need frequent stopping and it is a greedy plant needing ample .
The tradescantias and zebrinas are trailing plants with variegated leaves about 1 ½ in. long and ¾ in. across. Some of the tradescantias are liable to revert to unvariegated leaves and any unvariegated shoot should, be removed as detected, as otherwise they will grow so much faster than the variegated portions that they will eventually swamp the plant. This danger does not apply to the tradescantia known as `Rochford’s Quicksilver’, nor to the zebrinas. Too deep a shade may suppress the variegation, otherwise they will thrive in any situation. Trails willif placed in water and can be put several to a pot and watered in to make new potfuls. The plants soon become rather leggy and are best replaced every one or two years. You must make a hole in which to insert your (which should be about 2 in. long) as they are rather brittle and might break if you just pushed them in. The must be kept fairly moist until the have rooted, which takes about a fortnight. Tradescantias like plenty of water, but if kept dry the leaves will come small but quite well-coloured. Sideshoots appear whether you stop the plants or no, but, they will appear sooner, if you stop the main growths.
The eucalyptus most commonly grown as a house plant is E. cinerea, which could eventually make a small tree. It is very attractive with its white branches and blue-green leaves, which are nearly circular in young plants and lance-shaped when adult. To keep the plant within reasonable bounds it must be pruned hard every spring and the leading shoots that emerge at the top of the plant, must then be stopped, otherwise they will continue to grow and no lower growths will be formed. The plant should have a well-lit situation and be kept reasonably cool during the winter. Once in a 6-in. pot, it is advisable to keep it there, as otherwise the resultant plant might become too unwieldy. This entails regular feeding.
comosum variegatum is sometimes known as the . It throws up a clump of grassy leaves, which are nearly a foot long, but which reflex to give a fountain like effect. They are either cream coloured with a thin green margin or else they have green margins and a cream centre. The small white are often replaced with a tuft of leaves and if this is pinned down into a pot, it will soon take and the can then be severed, giving you a fresh plant. Keep these young plants somewhat on the dry side until they are well rooted, but well-rooted plants can take plenty of water during their growing season, although they are kept fairly dry from October until March. Small plants look rather grassy, but they grow rapidly and large plants are very impressive. They should be got into 5-in. as soon as possible and then potted on every other year.
is a low creeping plant, producing aerial like an ivy and it can be trained up walls in the same way. The leaves are small, about 1 in. long and 4 in. across, heart-shaped, and they completely cover the thin wiry . This plant thrives in shade and must, indeed, never be exposed to bright sunlight and similarly it must never be allowed to dry out completely, otherwise the leaves may shrivel and drop off. Overwatering is possible, particularly during the winter, but some moisture is essential even during this period. In mild parts of the country it will grow outside on a north-facing wall, so it has no objection to quite low temperatures.
Araucaria excelsa, theis in nature a very large tree, but it is very slow-growing as a house plant. It makes a perfectly symmetrical pyramid, with a central stem, from which, after every year’s growth, tour branches radiate horizontally from the central stem and, in their turn, produce symmetrical sideshoots, which are produced in opposite pairs all along these side branches. All these main and side branches are densely clothed with bright green needles. The plant must be rotated at regular intervals, so as to preserve its symmetry. The plant should never be pruned nor stopped and once in a 5-in, pot needs on every two or three years, and should be fed during the intervening period. The plant can be stood outside during the summer in a somewhat shaded situation, to great advantage. The plant must not dry out at any time, but on the other hand it does not require much water at any period, although more will be required when the new growths are elongating.
Other house plants that will thrive under cool conditions are two vine-like climbers,, the kangaroo vine, and Rhoicissus rhomboidea, while an attractive trailing plant is Plectranthus oertendahlii, with leaves that have the principal veins picked out in silver.