Greenhousing, Making the Best of the Growing Season

By Jos Van Hage

Many gardeners have a greenhouse as it helps to extend the growing season and enables us to grow plants that may otherwise be difficult because of our climate. Plants such as tomatoes, peppers, eggplants, and cucumbers do very well in a greenhouse environment as they enjoy even hot temperatures, a long growing season, and are frost tender. Other frost tender plants such as beans, melons and squash grow well in a greenhouse. In early spring greenhouses are used to start seeds and also get an early crop of lettuce, radishes, spinach, and other salad crops. I find that during the summer when temperatures become hot these same salad crops do better outdoors as they prefer cooler temperatures.

Greenhouses come in different forms such as coroplast, plastic, glass or fibreglass and they all do the same thing. Plastic greenhouses are cheaper in the short run but require more work as the plastic will need to be replaced; glass is nice but can break. Fibreglass and coroplast are both durable but the double walled coroplast is very good as it provides some insulation. A must for any type of greenhouse is good air ventilation so an automatic roof vent or having windows that open on opposite sides allowing air circulation is important. Good air circulation will cut down on disease as well as promote pollination. You also want to keep good spacing between the plants as this will help in the prevention of mildew, a common complaint in the greenhouse. Mildew is often caused from a high humidity. There are several ways to help with this and they are to do with the watering. You always want to water in the morning so that the water moisture evaporates quickly during the day preventing plants from being to moist during the cool night time temperatures. When watering try not to get water on the foliage of the plants and only water when the top of the soil becomes dry. Do not water unless the plants need it. If you see mildew on a leaf remove it right away before it spreads.

Another problem that tomatoes can have is blossom end rot which is a dark circular dead spot found at the blossom end of the tomato. A few possible causes such as a low calcium level in the soil, uneven watering, or extreme temperature changes can be the problem. Dolaprill lime which is a fast acting lime can be added to the soil to help with the problem.

Fertilizing plants at least once a week or more preferably twice in full growing season will help in healthy strong plants that produce a high yield. For fruit production you want to use a fertilizer with a lower first number (nitrogen) and a higher last number (potash). A favorite of mine that I have used successfully for many years is the 15-15-30 a water soluable fertilizer specialized for tomatoes. Another thing that should be done to promote high harvests is removing the suckers from staking tomato plants (indeterminate or those that grow tall), as they only suck away important nutrients that could be going into fruit production. Suckers are the shoot that grows directly above where the leaf comes from the main plant. These are pinched out as they appear. Bush types (determinate) tomatoes or the favorite hanging tomato ‘Tumbler’ do not have anything pinched off as every branch will produce. If the plant is producing lots of flowers but not setting fruit walk through the greenhouse in the morning gently shaking the plant for a few seconds which will move the pollen around.

A common pest in greenhouses is aphids. I always like to prevent the problem before it starts so hanging sticky yellow strips up will work. Aphids are attracted to the yellow color and when they are on the strip they stick to it. Also spraying the plants weekly with an organic insecticidal soap or end using "End All" should prevent the problem. You want to catch the first aphid and prevent it from producing more which will ultimately prevent any large problem. I find that aphids are first attracted to pepper plants so I grow all my greenhouse vegetables in big pots and when the peppers get aphids I remove them to the outside which seems to get rid of the aphids as well.

Jos

Email | Print | Facebook | Twitter | Digg | Del.icio.us