A greenhouse prevents the loss of heat from a structure by convection, that is, by trapping warm air inside the structure. Isolation is achieved by enclosing the structure with roof and walls made of glass or plastic sheets. In size, greenhouses can be small sheds to very large structures built on acres of land. As temperature inside a greenhouse is closely regulated, it is used to grow plants that require specific temperature conditions. A greenhouse is also useful for growing certain plants through the year, irrespective of the climatic conditions outside.
Tomato is the most widely grown vegetable in the world. Tomatoes need a good amount of sunlight and heat to thrive. Growing tomatoes in an area that does not enjoy sunny weather is difficult. Thus it is prudent to cultivate tomatoes in a greenhouse where the plant is given the ideal environment. Tomato plants should be planted directly in the greenhouse soil or in pots placed inside the greenhouse. Soil has to be a nutrient-rich mix of compost and fertilizer. Tomatoes need plenty of water initially. Even after the initial growth phase, the plants should be watered daily. Apart from these, tomato plants should be treated with pesticides as any other plant that is grown in outside environment.
Cucumber is another popular greenhouse vegetable. Being a spring or early summer crop, a cucumber plant requires higher temperatures for growth. The plant also requires good organic nutrition in the soil. The plant needs to be fertilized regularly so a sufficient amount of nitrogen and potassium reaches the fruits it bears. Cucumber plants can thrive in a great variety of soils. Watering has to be done carefully as excess water in a humid environment makes cucumbers prone to diseases. The vegetable plant must be inspected frequently for diseases and infections, with periodic use of preventive fungicides.
Sweet peppers originate from the hotter climates of Central America and Mexico. The plant needs a warm and sunny climate to thrive and is a good candidate to be grown in a greenhouse. Popularity of sweet peppers in modern cuisine makes them a good addition to any greenhouse. Peppers need a good amount of warmth and nutrition-rich fertilizer. Warmth in colder months can be obtained through a heating system in the greenhouse, and constant nutrition can be ensured by use of a good slow-release fertilizer. The ideal way to sow pepper seeds is in small pots and then transfer them to individual containers once they germinate. Peppers require regular watering and cannot tolerate being soaked in water so the soil has to drain well.
Aubergines or eggplants are related to tomatoes and sweet peppers and also thrive in a greenhouse. Aubergine needs higher temperatures than tomatoes and peppers to grow well. The best way to initiate an aubergine plant in the greenhouse is by letting the seeds germinate in water and then planting the seedlings in pots until they are about 4 inches tall. The fruits are heavy and hence the plant needs to be supported with stakes.