An A-Z Guide to Bulbs for the Greenhouse

Achimenes

These bright and pretty, easy-to-grow, long-lasting flowers in pink, purple and white are very popular for pots and hanging baskets inside the greenhouse. The tubers are available in mixture from January until April.

Plant them in a fine mixture of loam, peat, sand and some well-decayed manure. Cover them an inch deep and once top growth appears give plenty of light and regular watering. The tubular flowers appear on 15 to 18-in. stems and should be given some light support unless they are growing in hanging baskets. After flowering they can be stored dry in their pots in a temperature of about 10°C. until it is time to start them into growth again.

Begonias

Bletilla

Although many species of this genus, a member of the orchid family, require almost sub-tropical conditions, Bletilla striata, sometimes known as Bletilla hyacinthina, is comparatively hardy, though it may need the protection of a greenhouse in winter. It forms a tuberous rootstock and thrives best in semi-shady positions. It should be given well-drained loamy soil in which there is plenty of leafmould.

The leaves are hairy and the slender flower stems, varying from 6 to 12 in. high, produce during the summer, four or five nodding rose-purple flowers with narrow petals.

Apart from their use out of doors, bletillas are excellent subjects for the cold greenhouse. Water very sparingly in winter, only just enough to keep the soil from becoming bone dry.

Canna

This tall-growing plant owes its name to its erect stems or canes. Although it will not stand frosts, it is a useful plant for summer bedding in sheltered, sunny situations, and looks attractive when intermixed with other summer bedding subjects.

The thickish rootstocks should be started into growth from early February to April, preferably in a temperature of around 15 to 18°C. Cannas like a fairly rich sandy compost and moist growing atmosphere. Although they look first class in the greenhouse, they are at their best out of doors and can be moved to their flowering quarters from early June onwards.

Slugs and snails are the most likely pests. The foliage should be examined at frequent intervals and slug bait can be put down.

Among the first-class named varieties are those with scarlet, orange and yellow, yellow with dark spots, and orange-scarlet flowers, some having attractive purplish-brown foliage which, with the flowers, combines to make an exotic-looking subject.

Clivia

Of South African origin, these plants with their attractive clusters of funnel-shaped flowers on sturdy stems are easy to grow. There are several species, all flourishing in the cool greenhouse or on a window-sill, so long as they are kept free from frost.

Many useful hybrids have been raised. The best known species is Clivia miniata, which has several forms and is a native of Natal; the bright green strap-shaped leaves grow from 18 to 24 in. long and the 15 to 18-in. stem is surmounted with an umbel of twelve to eighteen campanulate scarlet flowers, each one having a yellow throat, making an effective display during the winter. Clivia nobilis is not quite so large as Clivia miniata and has orange-red flowers, the petals of which are tipped with green. The flowers of both are scented and sometimes followed by large, brilliant red berries.

A compost of two parts loam, one part decayed manure, plus silver sand and a dusting of charcoal, suits the plants, which like plenty of moisture during their growing period. They should be disturbed only when it is necessary to divide; in fact they seem to flower better when pot-bound. Well-established plants will benefit from a few applications of liquid manure when in full growth.

Cyclamen

Eucomis

This bulbous plant deserves to be more widely known. It has the common name of Pineapple Flower and makes an excellent pot plant. The wavy leaves, often as much as 18 in. long and 2 or 3 in. wide, are spotted purplish brown on the undersides. At the top of each sturdy 10 to 14-in. spike is a densely packed head surrounded with a little tuft of bracts.

Eucomis bicolor is a vigorous species, the greenish-yellow flowers being edged with purple. Eucomis punctata is a fine species, its creamy-yellow, star-shaped flowers appearing from July until September. The pleasing scent is particularly strong.

Eucomis like rich, well-drained gritty soil. In mild districts they can be grown out of doors in a warm, sheltered situation. A winter mulching of leafmould or weathered ashes will provide protection.

Freesias

Gladiolus

While it is possible to grow the large-flowered and primulinus types of gladiolus in the greenhouse, the smaller flowering and early species are the best for this purpose. Cultural, details for the hardy gladioli are to be found on Growing Flower Bulbs: Gladioli.

Corms should be planted in pots in November, four or five corms to each 5 or 6-in. pot. They should be kept under cool conditions and will then flower from mid-April onwards. The flowers of all are much daintier than the large-flowered type. Among the best is Gladiolus colvillei which has dainty crimson-purple flowers flecked with white. Gladiolus nanus can also be recommended and of its forms, which grow 1 to 2 ft. high, Amanda May, salmon pink; Blushing Bride, white, flaked crimson; Peach Blossom, pink; and Spitfire, scarlet, are all first class. All are excellent for cutting.

Gloxinia

Tuberous plants with large, bell-shaped flowers in crimson, violet and white marked with other colours, gloxinias are among one of the most decorative greenhouse plants. These should be treated in the same way as begonias, the tubers being started in pots and barely covered, in February and March, with a rich, well-drained compost. If a fertiliser has not been incorporated with the mixture, occasional applications of liquid manure during the growing season will prove beneficial. Avoid much watering until the tubers are in full growth and keep the receptacles shaded, potting on the plants as growth develops.

Gloxinias flower from June until September. It is important to keep the plants scrupulously clean, to minimise pests and diseases.

 

Haemanthus

Sometimes known as the Blood Flower, this is a greenhouse bulbous plant of South African origin which is easy to cultivate. It should be grown in the cool greenhouse, although in warm positions it will sometimes flourish outside.

The broad, thick, fleshy leaves are produced on 10 to 15-in. High speckled flower stems. Plant the bulbs in September and they will flower during winter and spring. One bulb in a 5-in. pot of sandy loam will produce a good effect, although several bulbs in a larger container provide the best display. The bulbs resent disturbance and it is unnecessary to repot more than once every three years or so. In such cases remove the top couple of inches of soil, and replace it with fresh material.

Haemanthus albiflos is pure white; Haemanthus coccineus, bright red speckled with brown and Haemanthus katharinae is brilliant red.

Hippeastrum

Hippeastrums, now so popular as house plants, can also be grown in the greenhouse with little heat except for an initial burst. Bulbs can be obtained which will produce flowers in pink, red, crimson, orange and white, as well as all these colours striped with white. They like a well-drained soil which is fairly rich in organic matter and succeed when potted one bulb per 6 to 8-in. pot in John Innes Potting Compost No. 3. You can also prepare your own potting mixture of 3 parts good loam to 1 part well-decayed manure, with some silver sand and bonemeal. Good drainage is ensured by placing an inch or so of broken crocks in the bottom of the pot. When potting, a third to a half of the bulb should remain above the soil.

Hippeastrums should be started into growth in the greenhouse from February onwards, preferably in succession until the end of April. After potting, soak the soil, but not the bulb, and place in full light in the greenhouse in a temperature of 15 to 21°C. Bottom heat, ie. heat given from the staging on which the pot stands, is best. Very little water should be given until the bud starts to show, when normal watering can be resumed. As soon as the buds begin to burst you can allow the temperature in the greenhouse to fall as low as 7°C. To lengthen the flowering period.

Continue to water the plant when it has finished flowering, giving it a feed of liquid manure each time until late August. After the foliage has withered, take the bulb from the pot, let it dry and store it in a warm place before potting it up again the following February for the next season.

Hymenocallis (Ismene)

These greenhouse bulbs are native of tropical America and are often known as Sea Daffodils. The bulbs should be potted in early March, using a mixture of turfy loam, decayed manure and coarse silver sand. Once growth is seers water should be given frequently and the temperature maintained at about 15°C. The bulbs should be partly rested during the winter by gradually withholding water. It is not necessary to disturb the roots annually; it is sufficient to repot the bulbs once in every three years, for the same bulbs go on flowering for a number of years. Hymenocallis calathina and its improved form Advance, with white flowers growing 2 ft. high, are the best for general purposes, while the variety Sulphur Queen has soft creamy-yellow trumpet-shaped blooms.

Ixia

The Corn Lilies, native of South Africa, are very valuable for cool greenhouse cultivation, for they flower in late spring and early summer in abundance and do not require special treatment. The wiry, but strong stems grow 15 to 18 in. tall, each producing six or more flowers of striking beauty with most having a prominent dark centre. The narrow foliage is an added attraction for indoor decoration.

Ixias can be given the same treatment as freesias, except that the pots are best plunged up to their rims in peat and left in a sheltered position or cold frame until February. When brought into the cool greenhouse and placed on a sunny shelf, they will soon produce a fine display. Like freesias, they can be purchased as mixed selections or by named variety.

Lilium

Nerine

Oxalis

These are easy to grow as pot plants in a cool greenhouse. Plant eight or nine bulbs to each 5-in. pot in a compost of sandy loam and leaf-mould, covering them to a depth of only about 1/2 in. After potting, keep in a cool place until growth appears and then move to the light. No water should be given until growth appears and then only sparingly, with an occasional application of liquid manure. There are a number of species but the easiest to grow are Oxalis adenophylla, 3 in. tall, with dwarf lilac-pink flowers and crinkled foliage, and Oxalis deppei, with dainty coppery-red flowers and clover-like leaves marked with bands of purple. Oxalis adenophylla flowers from April to June, well ahead of Oxalis deppei.

Sparaxis

Sometimes called the Harlequin Flower with richly coloured flowers and colourful foliage on 6-in. stems, sparaxis is easily grown in a cool greenhouse. Plant the corms in pots in October and treat them in the same way as ixias. Selections of mixed hybrids are available from nurserymen.

Sprekelia

Sprekelia Awnoshsiaa, the Jacobean Lily and a native of Mexico, flowers well in pots of sandy loam in the cool greenhouse. The bulbs are 2 in. in diameter and the vivid crimson-scarlet flowers are produced in March and April. These are orchid-like in appearance with six long petals, although growing on 18 to 24-in. stems. The bulbs, two thirds buried, should be potted up in February. Water freely when in full growth.

Tigridia

Natives of Mexico and Peru, these are interesting bulbous plants often known as Tiger Flowers because of their beautifully spotted and marked flowers. They make first-class pot plants and will flower from June onwards. They may also be planted out of doors in summer in sunny positions, and are described in more detail in the chapter on hardy bulbous plants.

There are a number of separately named varieties, but tigridias are usually offered in mixture.

Tritonia

This is a pretty genus flowering in June and July, with leaves about 6 in. long and slender stems growing 12 to 15 in. tall, with orange-shaded flowers shaped like broad, short funnels. Tritonias cannot be grown out of doors except in very mild districts, but can be cultivated in a cool greenhouse in the same way as ixias. Try crocata rosea or Orange Delight, a strong long-lasting variety of great beauty.

Tulipa

Vallota

This plant was once much in favour for growing on the window-sill where it proved of great value for its fine free-flowering abilities. Although often reaching 15 to 18 in. high, ValIota speciosa will, on occasion, produce scapes or growing stems up to 3 ft. surmounted with six to nine funnel-shaped, brilliant scarlet flowers. More often, however, the plants are grown in 5-in. diameter pots and produce three or four flowers on 12 to 15-in. stems.

It is not necessary to dry off the bulbs; in fact, part of the plant’s charm lies in its evergreen strap-shaped leaves, which are often 18 to 24 in. long. To keep the plants healthy, the bulbs must be liberally supplied with water during their growing period, and the soil kept just moist when the plants are at rest.

Bulbs should be potted from June to September, using a sandy compost containing decayed manure and leafmould. Repotting is not necessary more than once every three years. In alternate seasons, remove the top inch of soil, replacing it with fresh material.

Veltheimia

There are few species of this genus all of which may be successfully grown with very little artificial heat.

The broad leaves with wavy edges are 6 to 8 in. wide and the flower spikes, often 18 to 30 in. high, are not unlike the miniature Red-hot Pokers of the herbaceous border. These leafless spikes often carry thirty to forty or even more individual tubular florets which, in the case of Veltheimia glauca are red and yellow, set off by glaucous foliage, while Veltheimia viridiflora is deep flesh pink mottled green with bright green leaves.

The bulbs should be potted in August or early September and provided with a compost of good loam, some peat or leafmould and silver sand, with the addition of well-rotted manure. Start the bulbs in a low temperature and when there are signs of growth, heat can be increased.

Zantedeschia (Arum Lily)

08. July 2011 by admin
Categories: Bulbs, Greenhouse Gardening | Tags: , , , , , | Comments Off on An A-Z Guide to Bulbs for the Greenhouse

Follow

Get every new post delivered to your Inbox

Join other followers: