The need for at least one roof ventilator and one side ventilator in even a small greenhouse is must. In a well stocked house ventilation is required almost all year around. In winter the roof ventilator should be: opened an inch or two for a few hours around midday if the weather is dry and above the minimum temperature of the house. The winter ventilation is vital if we are using a paraffin gas or oil heater. As spring arrives roof ventilator should be opened more widely and for longer time in the day but the side ventilators are still kept close. In May the situation changes the main purpose of the ventilator is to keep the temperature below 250 centigrade. Side ventilators are now kept open. In high summer, besides ventilation shading also is required.

F. Supporting

Many of the most attractive specimens are either climbers or tall plants with weak stems. For this purpose giving support becomes essential. Such arrangements should be strong enough to support the plant in full fruit. Supports which are attached to the greenhouse may be either horizontal or vertical depending on the requirement. Sometimes such support systems are needed which are not attached to the structure of the house. Basic examples are wooden stake or bamboo cane. Instead of one cane 3 or 4 canes should be used around the plant to support it tall plants. Growing bags are a special case for which self supporting metal frames which stand around or over one bag are made available.

G. Pots and potting

Earlier there were just two basic ways of growing plants under glass. Some flowers or small shrubs were kept in pots but most flowering perennials, shrubs, vegetables and fruits were grown in border soil. The basic rules were followed. The stake or support in the ground was inserted prior to and not after planting. One can grow more plants in pots but now there is a trend to change over to modem technique of growing bag cultivation. They are consistent and sterile and are capable of giving high yields. These compost filled plastic bolsters are excellent for vigorous plants like tomatoes, cucumbers and melons, but they need special care as the rules for watering and feeding are quite different from the way one cares for plants in border soil. Containers can be of following types.

a. Clay pot, advantages: less likely to topple over, porous less likely to water log, traditional natural appearance.

b. Plastic pot; advantages: less likely to break if dropped watering is needed less often, decorative forms available.

c. Tub: these are large decorative container in wood, plastic or fibreglass for a shrub or a collection of smaller plants. Fill bottom with gravel before adding compost and water with care if drainage holes are absent.

d. Polythene sleeve pot: these are inexpensive and easily stored.

e. Peat pot: useful for potting on before transfer to garden, pot is biodegradable can be planted directly into soil or compost and no root disturbance.

f. Peat pellet: useful for seed sowing and potting on can be planted directly into soil compost; should be soaked in water before use.

g. Peat block: these are compressed cube of soil based or soil less compost; it needs careful handling and is no longer popular.

h. Growing bags: these are plastic bags filled with soil-less compost, drainage holes or silts are made in the sides and panels are removed from the top to create planting pockets.

i. Raised beds: these are useful where base is paved or soil is badly drained.



VI. General Care of Plants in Greenhouse

H. Growing media

It can be of any of the following types mentioned here.

1. Garden soil
Soil taken straight from the garden is not suitable for filling pots. It may contain the pests and weeds. A 4:1 garden soil/peat mixture can be used for a raised bed which should be changed after few years.

2. Soil based compost
Here sterilized loam and peat are blended with fertilizers time and sand.

3. Soilless compost
Because loam is difficult to obtain and its quality is variable, most modem composts are based on peat or peat and sand. These have several advantages over soil based ones.

VII. Maintaining the Greenhouse Structure

This is done for keeping the plants in peak condition and to inhibit pests and diseases. The routine should be to carry out an annual overhaul in autumn and to take an immediate action at any time of the year if there is an emergency.This includes the following schedule.

A. Autumn cleaning indoors
For this, the plants should be removed, then rubbish, old pots etc. to be removed and then a stiff brush, scrapper, sponge and a dilute warm water solution of disinfectant is recommended. Cracks, crevices, T-section bars in aluminium houses should be specially cleaned. Disinfectant should be spread and left for working for hours and then should be hosed down with help of long handled brush and plain water.

B. Autumn cleaning outdoors
Glass and framework can be cleaned using water and detergent or a dilute solution of a horticultural detergent with help of a long handled mop to reach the roof sections. Walls and base if present should be cleaned by scrubbing the bricks and block walls with water and specific cleaner. For wooden sides, algae and moss should be removed with a proprietary moss killer.

C. General maintenance
This includes more than just cleaning the glass, frame work shelves, staging etc. All iron and steel fittings, hinges and screws should be checked for rust and treatment. Replacements should be done as per the need. Draughts are a special problem so checking of vents and doors should be done. One can fit self-adhesive draught proofing strips, if they are not present. The wooden framework of the house should be inspected and the gutters need cleaning and repairing if necessary.

Looking after glass, wood, door, guttering are the other important activities which should be performed regularly as they otherwise lead to big unmanageable type of difficulties.


D. Feeding of greenhouse plants
Plants require ford to remain healthy. A number of elements are involved, the main ones being nitrogen, phosphates and potash. Commercial peat based composts contain all the essential nutrients and these last for 6-8 weeks after planting. Feeding Should then start, but how much and how often will depend on a number of factors.

Slow growing and dormant plants need little or no food as actively growing ones need feeding regularly. Liquid fertilizers are the best form for pot and growing bag plants. Solid feeds should be confined to the borders. Make sure that the compost is moist when feeding plants as applying fertilizer to dry compost can lead to injury. Foliar feeding is an interesting technique here, dilute fertilizer is applied directly on the leaves. Too little or too much fertilizer, both lead to specific types of problems, so fertilizer application should be done timely, judiciously and carefully.

E. Lighting
Most greenhouse gardeners rely solely on natural light. It is lack of light as well as low temperature which cause plant growth to slow down in winter. This is not just a matter f of dull days. Day length is also important. Most plants need illumination for 12-16 hours per day in order to maintain active growth. Installing light has several advantages in winter. The increase in the duration and intensity of light boosts seedling and young plant growth and also induces flowering in some types. The most important advantage is however that one can work in the greenhouse during long winter evenings. Here two warnings are necessary. One has to be sure that the lamps chosen are the one recommended for horticultural use, and the other point, that some plants require a period of short days and so may be harmed by artificially extending the day length in winter.

VIII. Greenhouse Plant Troubles
The warm and moist conditions within a greenhouse provide a paradise for many pests and diseases. Few natural enemies are present and the breeding rate of organisms can be amazingly high. There are times when one has to spray or ignite a smoke but a great deal can be done to prevent problems if rules of good hygiene are followed strictly.

For this the first and foremost point is to prevent trouble before it starts as never bring trouble into the house i.e. never use un-sterilized soil, or unsterilized manures. Inspect new plants carefully and take any remedial action which may be necessary before putting them with their plants. The house should be kept clean; for this a garden disinfectant can be used. Good growing practices should be followed by ensuring proper ventilation. Dry air encourages pests such as red spider mite and thrips saturated air encourages diseases. Watering should be done in morning so that leaves can dry before nightfall. Dirty rainwater should not be used for watering.

Border soil should be sterilized annually to prevent the build up of harmful organisms. Plants should be fed regularly for which potash is important. Plants should also be inspected regularly, by paying special attention to underside of the leaves.

If there are problems, than the golden rule is to tackle the trouble without delay. For this, first do not spray insecticide as minor attacks by caterpillar and leaf minor can be controlled by hand picking. Mouldy leaves and fruits should be removed. Then one should go for the right treatment if needed. Spraying, fumigating or dusting may be necessary. Pesticides are safe to use in the way described on the label with all precautions.

For this first we should make sure that product is recommended for use under glass and for the plant in question. Other important point is that treatment should always be done in right way, like do not spray or fumigate when the sun is shining close all ventilators before using a smoke take care with aerosols, spraying too closely will cause scorch, do not spray open delicate blooms, spray them roughly both above and below the leaves. Finally, always follow .the after treatment rules.


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