Principles of Green House Technology:

A greenhouse (also called a glasshouse) is a building where plants are grown under controlled micro environment. These structures range in size from small sheds to very large buildings. A miniature greenhouse is known as a cold frame.

A greenhouse is a structure with different types of covering materials, such as a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming visible solar radiation (for which the glass is transparent) from the sun is absorbed by plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall.

Purpose of the Green House

a)      To promote tomato growing in the cooler areas

b)      To promote the growing of tomatoes throughout the year in both cool and warm areas

Justification of the Green House Tomato Growing

a)   Growing tomatoes in a green house reduces disease infection and also raises the temperature. Tomatoes require an optimum temperature range of 20-25 0C during the day and 15-17 0C at night.

b)  In the green house, tomatoes may be fed with carbon dioxide easily. This increases yield and enhances quality.

c) Currently, most farmers grow tomatoes during the dry seasons, under irrigation.

In the green houses tomatoes can be grown all the year round

Advantages of a Green House

a)      Higher yields can be realized/intensive production per unit area

b)      High quality produce

c)      Minimized cases of diseases

d)     Market timing for optimum profit

e)      Production levels may be maintained all the year round

f)       Other warm season crops may be grown throughout the year

Other Crops Recommended in the Green House

a)      Coloured Capsicum  varieties  e.g. red, yellow etc.

b)      Cucumbit family e.g. Cucumbers, courgettes

c)      Onions e.g. bulb onions,

d)     Garlics

e)      Herbs and Spices  e.g coriander, parsley, celery

f)       Brinjals (egg plants)

Green House Methodology:

Types of Green Houses

Classification According to Size

a) Cold frame (miniature) green house for subsistence (less than 15×7 m)

b) Economic unit – 15mx7m

c) Commercia l- more than 15x7m

Classification according to lifespan and materials used

Frames can be covered with glass, rigid fiberglass, rigid double-wall plastics, or plastic film

a)      Permanent green houses

Metal frame-work and covered with glass with automated cooling/heating systems e.g. in research stations

b)      Semi permanent green houses

Metal frame-work but covered with plastic film/paper

Recommended for established farmers

c)      Temporary green houses

Wooden frame-work covered with plastic film /paper.

This is recommended for small scale farmers.

Classification according to structural shape of frame

A greenhouse can be attached to a house or garage; it can be a freestanding structure or gutter connected

a)      Attached Greenhouses

i) Lean-to. A lean-to greenhouse is a half greenhouse, split along the peak of the roof, or ridge line (Figure 2A), Lean-tos are useful where space is limited to a width of approximately seven to twelve feet, and they are the least expensive structures.

The disadvantages include some limitations on space, sunlight, ventilation, and temperature control. The height of the supporting wall limits the potential size of the lean-to. The wider the lean-to, the higher the supporting wall must be. Temperature control is more difficult because the wall that the greenhouse is built on may collect the sun’s heat while the translucent cover of the greenhouse may lose heat rapidly. The lean-to should face the best direction for adequate sun exposure.

Finally, consider the location of windows and doors on the supporting structure and remember that heavy rain might slide off the roof of the house onto the structure.


ii) Even-span. An even-span is a full-size structure that has one gable end attached to another building (Figure 2B). It is usually the largest and most costly option, but it provides more usable space and can be lengthened. The even-span has a better shape than a lean-to for air circulation to maintain uniform temperatures. An even-span can accommodate two to three benches for growing crops.

green-house2 iii) Window-mounted. A window-mounted greenhouse can be attached on the south or east side of a house. This glass enclosure gives space for conveniently growing a few plants at relatively low cost (Figure 2D). The special window extends outward from the house a foot or so and can contain two or three shelves.


b) Freestanding (detached) Structures:

Freestanding greenhouses are separate structures; they can be set apart from other buildings to get more sun and can be made as large or small as desired (Figure 2C).

green-house4You can also access a multi-media information on growing of tomatoes within a greenhouse via this link Greenhouse tomatoes growing.

Information Sources:

David Kuria ,horticulturist Ol Joro Orok ATC, MOA, Nyandarua West District,e-mail,Tel. 0714028024/0733791844;Titus G. Ng’ang’a Farm management , Ol Joro Orok ATC,MOA, Nyandarua West District, e-mail,Tel. 07230674 John Rimui Njau, practicing farmer, Nyandarua North District, e-mail Tel.0725111765.