Green House Gardening and What to Grow in Your Green House

Green House Gardening

There is much satisfaction to be had from green house gardening, but many gardeners are initially overwhelmed by the whole new ‘growing out of season’ experience.

Green house gardening


A number of out door bulbs are worth forcing in the greenhouse to get early flowering. These include crocuses, daffodils, Dutch irises, fritillaries, early-flowering gladioli, hyacinths, Lilium longiflorum, scillas and tulips. All bulbs must be encouraged to form roots before tops, so give them a moist, cool period either plunged in their pots under peat in the ground, or in a cellar or dark room. When the tops are forming bring them into the greenhouse and increase warmth gradually. Never let it get much above 60°F (l6°C) in temperature. Slightly cool off during flowering.


True alpine plants are simply those that grow between the areas of permanent snow and coniferous tree growth. Such places may occur at sea level in Arctic regions and in mountainous parts, such as the Alps themselves. In nature alpine plants are often protected by a thick coat of snow for many months and are spared the wind and rain characteristic of normal temperate winters. If you decide to try alpine plants you should bear this in mind and provide dry (it is dry under the snow) even temperature conditions during the plant’s dormant period.

An unheated greenhouse will do for alpines which need even temperatures in their dormant period, but some heat will prevent too much moisture and freezing roots. It is possible to separate sections of your greenhouse with polythene walls walls to provide varying conditions in different positions. The following plants will provide you with decorative plants at differing seasons. All can be grown in the cool or cold house which is frost free. Most like gritty well-drained soil with some stone chippings and they tolerate lime:

Armeria.  Thrift

Erica.  Heather

Gentiana.  Gentian






The glass-to-ground type of greenhouse is best adapted for tomatoes. They can be grown in the border, in pots, or by the ring culture method. This latter method entails using whalehide pots about 10 inches in diameter without bottoms, which are set on a deep layer of weathered ashes, clinker or gravel.

The roots which penetrate the layer beneath the pots will draw up water from it, and the plants are both watered and given a moist atmosphere by watering the gravel or clinker. It is essential to stake or tie the plants and to remove the shoots that appear between the side and main branches. Transferring the pollen by means of an artist’s brush helps to set the fruit. Container-grown plants should be stopped by pinching back the main stem after five trusses have set.


Cool stove to stove conditions are needed for cucumbers. The part-glazed greenhouse with some shade in summer suits them. The plants should be set in borders about a yard apart, and cucumbers thrive on a rich compost with plenty of mature manure and rotted straw. The plants are trained on wires, and side-shoots beyond the fruits are pinched out at two leaves distance. To avoid seeds all male flowers are removed. ‘Butcher’s Disease Resisting’ is a good variety.


Grapes are surprisingly easy to grow, even in small greenhouses. They can, when young, be grown in pots and left outside in the winter in plunge beds, being brought in ready for the following season with no ill effects. Wires are stretched from end to end of the house about 1 foot from the glass and the shoots  are trained along these wires. Eventually the vines may double back several times.

A traditional practice is to grow the vine in a bed outside the greenhouse and train it through a hole in the wall, so that the roots enjoy outside soil and the plant gets the greenhouse warmth for the ripening that it needs. One plant will eventually fill the greenhouse. A suitable variety for the greenhouse is ‘Black Hamburg’.

In the first season no grapes should be expected and the plant should be pinched back to 1 foot laterals from the main stem. These laterals are removed altogether during the dormant season, and the main stem shortened by one-third or half In the second year fruits are allowed to grow near the main stem and the laterals are again shortened, this time to two leaves’ growth beyond the fruit. The fruit is delicately thinned with special scissors to maintain in good condition. The plants should be copiously watered during growing and ripening.

After harvesting the laterals are partially pruned to half or a third of their length, and in the following winter again pruned, this time back to the first bud from the main stem. The main stem itself commences its journey very rapidly reaching often as much as six feet in the first season. During the first winter it is cut back by a third or a half Once it has reached the desired length it may be pruned back each year.

Other Fruits and Vegetables

Figs, melons, peaches and strawberries may all be grown in the greenhouse, and most types of greenhouses may be adapted for this purpose. Some varieties of lettuce are suitable for growing in winter and will survive low temperatures. These include ‘All the Year Round’, which may be overwintered in a cold greenhouse. Others, like  ‘Neptune’ are suitable for forcing in cool or intermediate houses for winter cropping. Mustard and cress will grow in any type of greenhouse. Herbs, such as parsley, may be grown in pots in a rich compost to provide more growth in winter than takes place in the open.

Cacti and Other Succulents

A large and varied range of plants are characterised by their ability to withstand drought by storing water in their fleshy plant tissue. Some, the cacti, have developed thick protuberant stems to retain water, and most cacti have dispensed with leaves altogether. Such plants are known as stem succulents. Others, which include members of the lily and spurge families, have developed fleshy leaves for storing water, and are known as leaf succulents.

Apart from the hardy garden plants, such as the sedums and sempervivums, most of these plants require cool green house gardening conditions with a winter temperature of about 40°F (4°C), or more. The growing compost should consist of 2 parts (by bulk) loam, 1 part sharp sand, 1 part peat, plus some pea-sized pieces of grit or charcoal to improve drainage, which is most important to succulents. For this reason clay pots are better than plastic. About a quarter of the depth in which the plant grows should be crocked at the bottom. Succulents generally like to be re-potted every two or three years, when all old soil should be removed.

Most cacti, except the popular Christmas cactus Zygocactus truncatus and the epiphyllums, like sunshine and their natural ability to store water enables most to withstand excessive dryness of atmosphere. Cacti and other succulents should generally not be watered at all for a month or two after November, and only very lightly, say once a month, thereafter till the growing season.

Propagation of leaf-succulents is by leaf cuttings; others may be increased by division or stem or pad cuttings. Offsets (young plants which form on their parents, as with Bryophyllums) may be detached and potted off.


Orchids used to be rich men’s hobbies, but not any more. Many can be purchased very cheaply, and many do not require high temperatures. For cool-house orchids such as cymbidiums and cypripediums, the winter temperature should never fall below 45°F (7°C). Cattleyas, the South American epiphytic orchids, need a minimum temperature of 55°F (l3°C) or more in winter.

Like cacti, orchids do not thrive on over-watering, and their roots are liable to rot. The rule is to water well when the compost appears to have dried out using soft water, preferably rainwater. Damping down the walls, floor and staging helps to create the correct degree of moisture in the atmosphere. In winter, watering is cut down to about once a month or even less according to conditions. There is a knack to potting orchids.

In winter light is needed, but in spring and summer guard against too much sunlight. Good air circulation around the plant is vital, especially in spring and summer, but draughts must be prevented.


The accent for ferns is on shade and moisture. A fine-atomising spray can be used for general damping down, and the plants should be kept out of direct sunlight. A position low down in the green house on moist gravel or ashes below the staging with bottom ventilation suits them best.

A suitable compost is 2 parts peat (by bulk), 1 part loam and 1 part silver sand or grit. Potting is best done in spring before the new growth commences. Plants may be divided with a sharp knife at this time. Half-hardy ferns require a winter temperature minimum of 40°F (4°C), and truly tender ferns need a winter minimum of 60°F (l6°C). Never allow ferns to dry out completely.

Some ferns suitable for a greenhouse with a winter minimum temperature of 40°F are:

ADIANTUM (maidenhair fern) The delicate foliage of these ferns and their cheerful pale-green colour makes them very attractive.

ASPLENIUM (spleenwort) A. bulbiferum is the popular plant that carries young plants on its fronds which can be potted off to propagate it.

PTERIS Another easily grown and popular fern with several different forms, the most well-known being albo-lineata, which has a central white line down the long, narrow fronds.

Annuals and Biennials

Many garden annuals can be sown in a greenhouse in autumn to obtain flowers the following spring. These include such plants as cornflowers, larkspurs, nicotianas and nigellas. In the same way, flowers can be kept in bloom later in the season by sowing in late spring. Early spring colour in the cold greenhouse can be obtained by over-wintering such plants as wallflowers sown in the late spring.


Many hardy perennials can be forced into earlier bloom in heated or unheated green houses. Particularly suitable are Solomon’s Seal and Primula denticulata.

Perennials which are not so hardy can often be saved by over-wintering them in the greenhouse.

02. September 2010 by Dave Pinkney
Categories: Greenhouse Gardening, Orchids | Tags: , , | Comments Off on Green House Gardening and What to Grow in Your Green House


Get every new post delivered to your Inbox

Join other followers: