CULTIVATION SMITHIANTHA

The time to start the tubers into growth is late winter or early spring, but the point to bear in mind is that a temperature of 6 5 ° F (18°C) is initially required, and when the shoots appear a minimum temperature of 55°F (13°C) is needed for growth to continue. Tubers started in late winter will usually bloom in late summer and early autumn. Tubers started in spring will bloom in autumn. If you do not have the facilities to maintain a minimum temperature of 5 5 ° F (I3°C) during early spring it is better to delay potting until mid-spring so that the shoots do not appear until the weather is warmer.

Make sure the compost is moist but not wet and do not water until absolutely necessary, as too much moisture at this stage before any appreciable root growth has occurred can result in tuber rotting. Place the pots in a temperature of 6 5 ° F ( 1 8 ° C ) until shoots appear, after which the plants can be moved to a slightly cooler place. A temperature of 6 0 °F (15°C) is ideal.

The tuber should be placed on its side in the compost about in (13 mm) below the surface, using JI potting compost No.2 or compost E6. Pot four tubers in a 5 or 6-in (12.5 or 15-cm) half-pot, which is quite adequate for the root run, and gives a better balance of pot to flower.

Apart from watering as required, the plants do not require any further attention until they have flowered. When grown in a greenhouse they should be given light shading in the late spring and summer months. When the plants have finished flowering, they should be allowed to dry off gradually until the leaves begin to wither away, at which stage withhold water altogether, and allow the compost in the pots to become completely dry. The pots can be stored under the bench in the greenhouse (providing you can maintain a minimum temperature of 4 5 ° F / 7 °C on average), laying each pot on its side.

The tubers will not come to any harm with an occasional short spell at 4 0 ° F (4°C) if the pots are bone dry, but should not be kept in temperatures below 4 5 ° F (7°C) for weeks on end. At the end of the winter knock the soil out of the pots and carefully sort out the tubers, which should then be started into growth as already described.

CULTIVATION PRIMULA

Primulas are grown from seed sown in well-drained pots using JI seed compost or a soilless sowing compost. The seeds are very fine and should be sown on the surface, after which tap the pots lightly on a solid surface, so that the seeds settle into the compost. Do not shade the seed pans but leave exposed to the light, but not direct sunlight, covering with a sheet of glass or a plastic bag.

As soon as the seedlings are large enough to handle they should be pricked out into boxes, if you are growing a fair number, or alternatively into 3-in (7.5-cm) pots, using JI No.2 or equivalent. At this stage it is most important to ensure that the seedlings are planted at the correct height, i.e. the crown of the plant should be level with the surface of the soil. If the crown is below the surface the plant will rot, and if above the surface it will not stand upright. The crown is the junction of the leaves with the stem. When the small pots are well-rooted, pot into 4-in (10-cm) or 4'/2-in (11-cm) pots, or if you have pricked out into boxes, transfer first of all to З'/г-in (8.5-cm) and later to 4'/2-in (11-cm) pots. For this final potting use JI No.2 or compost E6.

The sowing and potting culture already described applies to all six of the primulas with which we are concerned, but the growth requirements differ slightly, and at this stage it is necessary to differentiate. P. nialamides, P. kewensis and P. sinensis are best sown from early to late spring; P. obconica from late winter to mid-spring; and polyanthus and primroses late spring to early summer. All the primulas should be kept in a frame throughout the summer, and shaded from direct sunlight. At the beginning of autumn remove from the frame into the cool section of the greenhouse at first, until the weather becomes colder, then move P. obconica, P. kewensis and P. malacoides into the warmer section, where an average temperature of 45°F (7°C) is maintained. A drop to 4 0 - 4 2 ° F ( 4 - 5 ° C ) on very cold nights will not damage the plants. On the other hand P. sinensis requires a higher temperature, about 5 0 - 5 5 ° F ( 1 0 - 13°C). Polyanthus and primrose plants are kept in the cool section throughout the winter, as they are both hardy plants and will in fact stand frost.

Primulas are very useful plants for house decoration because not only are they attractive and colourful, but they flower from late winter to spring, a period during which flowering pot plants are not easy to find.

P. obconica will flower for months, but unfortunately has the disadvantage that it causes a skin rash to people who are allergic to the chemical secreted in the hairs on the underside of its leaves, and if you are one of these people always wear gloves when handling the plant.

A l l these primulas are treated as annuals and the greenhouse varieties are scrapped after flowering, but the polyanthus and primrose can be planted in the garden where they should bloom for years.

CULTIVATION LANTANA

The best way to start with lantanas is to buy a plant, which will usually have been raised from a cutting taken the previous year. If the plant consists mainly of new green growth it will have been a summer cutting, but if the growth is woody it will be a cutting from the previous spring.

If necessary shorten the shoots back to two pairs of leaves, assuming that your purchase has been made in spring, to give the plant a good shape and to make it bushy. Lantanas have a tendency to make straggly growth, and any weak growths are better removed altogether. The pruning of the plant is most important if you wish to produce a well-balanced attractive flowering plant, and if it is done in late spring you will be rewarded with more prolific flowering in summer.

Lantanas are propagated by cuttings which are taken in the spring or autumn. They are taken in the usual way by cutting immediately below a node about 3 - 4 in ( 7 . 5 - 10 cm) from the growing tip. Remove all the leaves except the top pair and root in a suitable cutting compost using a hormone rooting powder to ensure success. Cover with a plastic dome or a polythene bag for about two weeks, and when it can be seen that the cuttings have made some top growth they should be potted in 3'/2-in (9-cm) pots in compost E6 or JI No.2.

CULTIVATION OF KALANCHOE

Kalanchoes are grown from seed and can be raised quite easily; and should you wish to retain a particular plant it is possible to take cuttings, which are not particularly difficult to root. Sow seed in spring in any type of sowing compost, covering the seed very lightly, in a temperature of 6 0 - 6 5 ° F ( 1 5 - 18°C) and enclose in a plastic bag or cover the seed pan with a sheet of glass, and remove these coverings at the first signs of germination. As soon as the seedlings are large enough to handle, pot in 2'/2-in (6-cm) pots; they are slow-growing plants and this size of pot will probably suffice until the end of the summer or even the following spring. Dwarf varieties never require more than a З'/г-in (9-cm) pot and will grow for two years in this size, after which it is usually better to discard them.

Cuttings can be taken during the summer months. If left in the cutting medium for six to seven weeks, they should be well rooted and ready for potting in 2'/2-in (6-cm) pots.

For cuttings, select strong shoots about 2 in (5 cm) long, and cut below a node. Remove all the leaves except the top five, and, after dipping in a hormone rooting powder, insert about Чг in (13 mm) deep in a cutting compost. Keep the cuttings enclosed inside a plastic dome or a plastic bag for about three weeks and then expose them to the air for another three or four weeks before potting.

Kalanchoes tend to grow a single stem, and to obtain bushy plants it is necessary to stop the growth by removing the tip of the stem. This should not be done until the cuttings have made at least 1 in (2.5 cm) of growth. Side shoots will appear in due course, and when these have made sufficient growth remove the growing points of these as well. If you only wish to grow a few kalanchoes it is probably better to buy the plants and propagate your requirements by cuttings, which are very easily raised, rather than grow them from seed, particularly as it takes about eighteen months to grow a good flowering plant.

Kalanchoes require a minimum temperature of 45°F (7°C) during the winter but they w i l l not thrive if kept at this temperature. To make satisfactory growth they require a temperature of 6 0 - 6 5 ° F ( 1 5 - 18°C); consequently they need to be kept in a propagator in the greenhouse if they are to flower satisfactorily during the winter months. Once they have been brought into flower they can be put in a cooler temperature to retard growth and prolong the flowering period.

CULTIVATION OF STREPTOCARPUS part 2

Ideally the plants should be grown in a light airy atmosphere averaging about 65°F (18°C) and lightly shaded from strong sunlight. Given these conditions plants will continue growing the whole year round and will also flower for about three-quarters of the time. The usual procedure, however, is to allow the plants to dry off, after the middle of autumn, and from then onwards they are kept as dry as possible, without being allowed to dry out completely until growth is re-started in the spring. In this dry state plants can be wintered in the greenhouse at temperatures as low as 40-45°F (5-7°C) without harm. Streptocarpus make little or no growth at temperatures below 60°F (15°C) especially when dry; consequently the plants remain in a dormant condition and tend to lose their larger leaves. Once you have raised a batch of plants from seed you can propagate the best plants by means of leaf cuttings. Propagation of plants by leaf cuttings is carried out either by cutting the leaf across into three or four sections and pushing the cut edge of the leaf into the cutting compost about Чг in (13 mm) deep, or by dividing along the central vein and inserting the cut edge of the leaf obliquely to a depth of 1/2 in (13 mm). Plantlets should grow from the bottoms of the sections in about 4 to 6 eeks, and when they have made sufficient root they should be detached and potted in 2 1/2-in (6-cm) pots.

If you wish to keep a continuous stock of streptocarpus it is as well to raise a few new plants each year, either from seed or from cuttings, because although they are perennials plants grown in pots do not usually thrive after the third or fourth year, and even if they do they become too big and require too big a pot to be useful for house decoration. A wellgrown plant will require a 6-in (15-cm) pot in its third or fourth year, after which it will require an even larger pot; therefore plants should be discarded after the fourth year, as a general rule, unless you have some special reason for keeping a plant.

Cultivation of SOLANUM part 2

By early summer the plants should be in flower and at this stage it is better to keep them outside, in a position where they are shaded from the midday sun, in the hope that the flowers will be pollinated by the insects, rather than in the greenhouse, where insects are not encouraged. The crop of berries the plant will produce is entirely dependent on how well the flowers are pollinated. While the plants are flowering it is essential that the pots are kept well watered, and not allowed to dry out. The star-shaped flowers are white, and although numerous they are so small that they appear insignificant.

When the berries have developed satisfactorily the plants can then be brought inside the greenhouse which will speed up the growth. The berries when first formed are green in colour and they gradually change through yellow and orange to the ultimate familiar orange-red colour.

Solanums require plenty of light but they last longer if kept in a temperature range of 50 -60°F (10 - 16 ° C) during the autumn and winter months. The best time to buy a plant is in the autumn when it is bearing yellow to red berries and you are able to see how well-laden it is. The following spring, after taking any cuttings you require, the plants should be pruned by cutting back the stems to about half their length; and, as soon as new growth appears, either pot on into a larger size pot or preferably remove the old compost from the roots and repot in new compost.

CULTIVATION OF STREPTOCARPUS

The best way of starting a collection of streptocarpus plants is to raise them from seed, which is easily obtainable. Plants can be raised from seed without difficulty, whether you possess a greenhouse or not, because seed can be sown at any time between midwinter and mid-summer. Seed sown in mid-winter in a temperature of 68 - 78°F (20 - 25°C ) should produce flowering plants in summer. Alternatively, seed may be sown in early summer without heat to produce flowering plants for the following year. If you can it is better to sow seeds in mid-winter, because not only will these produce plants which will flower the first year but by the following year they will be much larger plants and will usually provide a continuous mass of flowers from mid-summer until early winter. The seed should be sown on the surface of a soilless seed compost and, either pressed into the compost, or covered very lightly with a fine sand. If you decide to press the seed into the compost, use an implement to which the seeds will not adhere and, after completing the operation, wet the surface slightly with water, by means of a fine spray, which will help to bed the seeds down in the compost. Enclose the seed pan in a plastic bag until the first signs of germination, which should be in 12-14 days if the temperature has been between 68 and 78°F (20-25°C ) .

The seedlings should then be pricked out into 4 1/2-in (11.5-cm) half-pots as soon as they are large enough to handle - the sooner the better - using compost E6. The seedlings are very slow-growing but when they are about three months old should be large enough to pot into 2'/2-in (6-cm) pots in compost E6. Potting on is only necessary when the pots are full of roots, and this will vary from plant to plant, but the size of the top growth is usually a good indication. When the plant has made good leaf growth it is time to look at the root growth. Your plants are not likely to require larger than З 1/2-in (9-cm) pots during the first year, from seed sown in mid-winter to early spring, but the following spring should be ready for potting on into 4 1/2-in (11.5-cm) or 5-in (13-cm) pots. Be guided by the size of the plant and the amount of root growth both for when to pot and for the size of pot to use.

Cultivation of SOLANUM

To grow plants from seed sow in mid-winter at 68-78° F (20 -25° C) and provide an adequate temperature of 60-70°F (15-21°C) while the young seedlings are developing.

Propagation by cuttings is carried out in spring, taking stem cuttings about 2- 3 in ( 5 - 7 . 5 cm) long and, after stripping off all but the top three or four leaves, insert the stem of the cutting about in (13 mm) deep in the cutting compost. It is always beneficial to dip the cuttings in a hormone rooting compound as this speeds up the formation of the roots.

When the young plants are growing in the spring they should be kept bushy by pinching out the growing tips from time to time. Whether growing seedlings or cuttings the first potting will be into 3 or ЗУг-in (7.5 or 9-cm) pots followed by a final potting in 4 or 5'/2-in (10 or 14-cm) pots, in both instances using compost E6 or JI potting compost No.2.