Bulbs corms and tubers

Everyone loves bulbous plants in winter and early spring, and few of us fail to be impressed by the showy tuberous begonias or the cyclamen, hippeastrums and gloxinias in their season. Even the less widely grown but no less handsome Haemanihus, LacfienaJia, Nerine and VoJloia rouse the greatest enthusiasm when seen in flower. It is the dormant period of the bulbous plant that is its undoing. A bulb, tuber, corm or rhizome is a storage vessel, where the essentials for next year's flowering are kept safely until the favourable season for growth comes round again. Many of the most exotic bulbs from the southern hemisphere adapt fairly readily to a dry period of rest during our winters, instead of enduring a summer drought at home. However, under glass it is up to us to signal the changing seasons and this is where we often fail, It takes some foresight and an organised approach to grow the more tender bulbs successfully year after year, which is the way that brings real satisfaction.

Although generally speaking the spring flowering bulbs are planted or re-potted in autumn and the summer flowering ones are planted in spring, some fleshy rooted plants are never wholly dormant and others have a very brief rest, which does not fit in with the commercial arrangements for dry bulbs. For those who become interested in the more unusual bulbous plants, there is plenty to learn, quite apart from the possible thrills of travelling to see such plants in their native habitat. The serious collector of rare bulbs often has a bulb frame. This is a raised bed of freely draining soil, which can be protected from the rain or cold at the appropriate seasons for summer ripening or winter dormancy. Here the bulbs can be grouped according to seasonal behaviour and allowed to grow naturally. This method does not create a show of bloom at any one time, but it does allow the best development of the smaller rarer bulbs, the habits of which are sometimes little known. Every bulb has its preferred position in the soil and most will adjust themselves to their natural depth in time, no matter how they are planted. This can be startling, as those who have raised bulbs from seed will know. After sowing seeds in a pot, one may find small bulbs in the gravel or capillary bench beneath it.

Although the idea of raising bulbous plants from seed is usually rejected by the beginner, it is not necessarily a slow process. The

Iris reticulata 'Cantab', a small hardy bulb suitable for the unhealed greenhouse (see p. 54).

beautiful LiJium philippinense can be flowered in nine months; freesias flower in seven months from a spring sowing and are very easy to grow. The fifteen or sixteen months it can take to raise a hybrid cyclamen from seed is more exacting, but some of the smaller newer hybrids are very much quicker.

The problem of how to rest a cyclamen corm always provokes conflicting advice, which only goes to show how adaptable fleshy rooted plants are to any steady regime. The secret is to keep them dry but not totally dry, from when the leaves start yellowing until that awkward moment when everyone is on holiday in August and the cyclamen is ready to be re-potted. Do not worry; leave it in the shade outside the back door where the rain will reach it, and you will be reminded to re-pot it on your return.

The small hardy wild cyclamen species, sometimes grown in pans in the unhealed greenhouse, can be difficult to start into growth when bought dry and may remain dormant for a year, which is disconcerting.

Begonias have tiny seeds and need warmth from the time they are sown in January, and so it is much less demanding to grow them from tubers in spring. The same is true of gloxinias. If they are to be enjoyed again the following year, they must be dried off gradually in October, so that the fleshy roots ripen and the foliage dries off completely before they are stored. They can remain in their pots or be put in dry peat and kept frost free, preferably at a temperature around 10°C (50°F). They are started into growth again in March. The fascinating Rechsteineria leucotrichu is a less well-known plant that is easily raised from seed in spring and may have a small flower in its first season. It has a corm that grows larger each year and needs only a fairly brief dry rest in midwinter in the cool greenhouse.

In an unheated greenhouse only the hardy bulbs can be grown in winter, but they will flower several weeks earlier than those in the open. Amongst the smaller hardy bulbs that are attractive in pots in January are the early crocus species and Iris histrioides 'Major', followed by the yellow I. dan/ordiae and the scented I, reticulata. One of my favourites is the scarlet multi-flowered Tlilipa praestans, but there are plenty to choose from besides the obvious hyacinths and daffodils.

The Vallofa is an evergreen bulbous plant that is shy-flowering until pot-bound and may be difficult to start if sold as a dry bulb. The big scarlet flowers in late summer are worth having. Another evergreen with fleshy roots is Clivio and this too can remain in the same pot for years. Its handsome orange or yellow flowers usually appear in late spring.

Perhaps the most spectacular of all glasshouse bulbs are the Hippeostrum hybrids (often wrongly called Amaryllis) that produce the largest flowers in scarlet, white, pink or orange, to silence the most querulous visitor. They often manage two spikes of Four flowers each, although they occasionally miss a year and lose friends that way. Early spring is the planting time, except for those specially prepared for Christmas flowering, which will join the others in blooming in April and May in subsequent years, They need to be gradually induced to rest in September, until they show signs of life in spring. Some obstinately remain evergreen and all need 10°C (50DF) in winter.

Other fleshy rooted flowering plants to try in the warmer greenhouse or conservatory are Acfiimenes, Gesneria, GJoriosa, Hae-manthus and Smithianilia. Suggestions for cooler conditions would include the winter flowering Laclienalia, hybrid nerines flowering in autumn and the handsome Velfheimia, which are ornamental through the winter and flower in spring. In an unheated or just frost-free greenhouse, the nearly hardy bulbous plants sometimes grown outdoors are worth considering. These include Agapanthus, Ixia, Nerine boivdenii, Sparaxis, Strep-tanthera and Tigridia (see p. 7).

Climbers and shrubs

There is no distinct division between climbers and trailers under glass, or indeed between climbers and shrubs if the latter can be persuaded to cover a wall. In a conservatory climbers give a furnished look and may also be used to give shade. The passion flower (Passi/loro coeruiea) is particularly useful for this (see p. 2), All climbers and shrubs planted in (he ground under glass will have to endure frequent and severe pruning, if they are not to overwhelm the place quite soon. Nevertheless, it is a mistake not to grow any climbers and hard-wooded plants.

In a small structure space is so important that one must either confine the roots in a pot or tub or limit oneself to one climber trained up to the roof or back wall. All the favourite conservatory plants are inclined to be rampant. The passion flower can be confined to a tub for a time and pruned hard back in winter. The same is true of the sweet-scented /asminum polyanthum that will root at every joint and grow twelve foot in a season, although young plants blooming in a 5-inch pot look innocent enough. The pale blue Plumbago capensis is by nature a big sprawling shrub with a long (lowering season, ll is quick and easy from seed or cuttings, takes hard pruning and will even submit to a pot, but cannot really do itself justice that way,

The Australian blue bell creeper (Sollya heterophylla) also has pale blue flowers and grows quickly from seed, but is of modest proportions. The beautiful Lapageria rosea, the national flower of Chile, must have a lime-free soil. It is evergreen with small neat leaves, and is slow-growing when confined to a pot. It likes shady cool conditions and the rosy pendant flowers are striking. (See p. 6).

There is much lo be said for a modest climber that dies back and makes a fresh growth from the root each year. Nature has limited its scope and you do not have to harden your heart and chop it down. Gloriosa superba and particularly G. rothsehiidiona is always greatly admired and may reach 6 ft (1.8m), but is a dry root for half the year.

TropaeoJum tricolor from Chile is a tuberous rooted climber of moderate vigour that dies down in mid-summer and rests until growth starts again. Light support will be needed for the twining growths wreathed with scarlet and black flowers in spring.

Fuchsias have been mentioned in other chapters and can be trained to any shape, but F. procumbens from New Zealand is a curious trailing plant for pots that few would recognise as a fuchsia. The yellow and purple flowrers are followed by red berries.

Those with a wall to cover in a sunny conservatory may be attracted by bougainvilleas. If happy, they ramp with thorny branches, but if unhappy they may forget to flower and be covered with greenfly. Plants as diverse as Begonia /uchsioides and zonal pelargoniums can be trained against a wall, and the important thing is to choose a plant that is not too attractive to pests. One of these, the orange flowered Streptosolen jamesonii, is an amenable bush for training upwards, and its hanging flowers look their best from below.

A group of climbers that are not too thrusting in a small space are the hoyas. Their clustered blossoms look more like wax or icing sugar than any form of plant life. Hoya beJIa is a tricky but beautiful basket plant for the warm greenhouse and H, ccirnosa a less demanding climber in a pot in cool conditions.

Small shrubs in pots often arrive as gifts, such as the Christmas azaleas, and it becomes a matter of pride to keep them from year to year. Plunged outdoors in light shade from June to October and re-potted if necessary in April, they can be kept going for years by those who manage never to forget to water them. They should have 7°C (45°F) and a moist atmosphere to bring on the bloom.

The modern poinsettia (Euphorbia puJcherrima] is less demanding than its forebears, but prefers a temperature of 13°C (55° F) and regular watering. After a nearly dry and slightly cooler rest in late winter it can be kept for another year, if repotted in April and kept warm and damp. It will flower later and be much larger, as it is grown commercially with chemical dwarfing and controlled day length (see p. 38).

Hibiscus rosa-sinensis is now a popular house plant that flowers for months but needs 13°C (55°F) in winter.

Camellias are irresistible in flower and valuable in a north facing cool or cold conservatory. They are best outside in summer as they are hardy plants only needing protection for their winter flowers.

For spring the mimosa best suited in size and slowness of growth to a confined space is Acacia armata, with narrow stems of small leaves dotted with little mimosa puffs. Perhaps the dwarf pomegranate Punica granatum 'Nana' quickly grown from seed to flower at 3 inches tall (7.5cm) is the nearest thing to a mini shrub designed for the beginner in a mini greenhouse.

Building Your Own Greenhouse

Building Your Own Greenhouse

You Might Just End Up Spending More Time In Planning Your Greenhouse Than Your Home Don’t Blame Us If Your Wife Gets Mad. Don't Be A Conventional Greenhouse Dreamer! Come Out Of The Mould, Build Your Own And Let Your Greenhouse Give A Better Yield Than Any Other In Town! Discover How You Can Start Your Own Greenhouse With Healthier Plants… Anytime Of The Year!

Get My Free Ebook


Post a comment