Tomatoes are one of the most popular garden vegetables in the world. They adapt well to confined spaces and require a narrow temperature range to produce the best fruit.
Gardeners must also regulate additional factors such as humidity and ventilation to get optimum results from tomatoes. These properties make tomatoes especially common greenhouse plants.
A tomato plant is any member of the species Solanum lycopersicum, which currently has about 7500 varieties.
They are warm weather plants, but are commonly grown in greenhouses in cooler climates.
Tomatoes grow as a perennial in their native South America but they can grow as an annual much further north
Tomato plants are a sprawling vine that commonly grow to 10 feet in length, although they are rarely allowed to reach this size in greenhouses.
A greenhouse is an enclosed structure covered by clear materials such as glass or plastic.
These materials are specifically designed to allow light to pass through them while preventing heat from escaping.
This means that the temperature and humidity within the greenhouse is typically much higher then that of the outside environment.
Greenhouses vary greatly in size, and are available to both commercial and private gardeners.
The ideal temperature for growing tomatoes is between 75 and 85 degrees Fahrenheit.
Temperatures below this range restrict the growth of tomatoes and the size of their fruit.
Cooler temperatures also increase the risk of fungal diseases on tomato plants, especially gray mold.
Greenhouses typically use heating systems with fans to provide a constant flow of air over the tomatoes, keeping the plants within a narrow temperature range.
It is generally impractical to maintain plants within a temperature range of 10 degrees Fahrenheit or less without fans.
Tomatoes require cooler temperatures at night, with the ideal range being between 60 and 70 degrees Fahrenheit.
Temperatures above this range are less likely to cause harm to tomato plants, but it is critical that the temperature not drop below 60 degrees Fahrenheit.
Cooler temperatures prevent tomato plants from developing a strong root system and producing quality fruit.
Temperatures below 60 degrees Fahrenheit also significantly increase the risk of mold, blight and fungus.
Greenhouse tomatoes are especially sensitive to cooler temperatures, while field varieties tend to have a greater tolerance for cold weather. Tomato varieties specifically developed for cold weather are not typically grown in a greenhouse.
The heat retention properties of a greenhouse often mean that overheating is more of a problem than insufficient heating for tomato growers.
The maximum daytime temperature in which tomatoes can grow effectively is about 95 degrees Fahrenheit.
Temperatures above this level restrict root growth and cause the fruit to have abnormal colors, both on the outside and inside of the fruit.
Greenhouses that grow tomatoes in warm climates typically need a higher ceiling to allow the warm air to rise away from the tomatoes.
Greenhouses with tomatoes routinely keep their windows open during warm weather. An active ventilation system is also needed to push warm air out of the greenhouse.
The enclosed environment of a greenhouse causes it to have a higher humidity level than the outside environment.
Gardeners often use evaporative cooling methods such as fans to evaporate water.
The process of evaporation uses energy, which also reduces the temperature of the air.
Evaporative cooling also reduces the cost of heating and cooling the greenhouse.
The plants themselves can also be used to regulate the temperature within a greenhouse.
A greater amount of space between plants creates more ventilation, which reduces the temperature of the air.
Greenhouse gardeners often prune the bottom leaves of a tomato plant to allow greater ventilation within the spread of the plant.
Pruned leaves must be removed from the greenhouse to minimize the spread of disease between plants.
Greenhouse gardeners in cool climates often need to install artificial heating methods for tomatoes.
In addition to fan-based heating systems, heating pipes are a common method of raising the temperature of the soil.
These pipes lay along the surface of the ground or they may be buried at a shallow depth.
Warm air from a heat source circulates through these pipes, raising the temperature of the soil and air.
The warm air rises to the top of the greenhouse creating airflow in an upward direction. This method is highly effective at heating tomato plants since the warm air moves past the plants on its way towards the ceiling.