Herbs and Vegetables in the Winter Greenhouse
Herbs and Vegetables in the Winter Greenhouse
By Tom Eckert, Dillsburg, PA
It is possible for the hobby greenhouse grower to enjoy many types of vegetables in the winter greenhouse, however a favorite, the tomato and pepper are usually not one of them. The shortened photoperiod and cool temperatures combine to discourage tomato and pepper from setting flowers or ripening their fruit. Natural pollinators -bees- are absent; and the pests – white fly and aphids – can be abundant if not controlled. And then levels of carbon dioxide needed for photosynthesis are low in the un-ventilated hobby greenhouse. Disease can thrive in the high humidity of the greenhouse.
Do not be discouraged, with choosing the right varieties of herbs and vegetable to grow, fresh vegetables can be enjoyed from fall till spring when the outside garden is idled.
You can extend the tomato season by digging up your tomato plants from the garden, potting them up and moving them inside. However, this in not too practical for most tomato varieties in the gardens grow into vary large plants usually 6 foot tall and about that wide.
There are a few tomato varieties bred to be grown in pots or 5-gallon buckets. These tomatoes are many times referred to as patio or bush tomato. The “better bush” is one example that produces 3 to 4-inch red fruits on a bush of some 4-foot tall and about 3- foot wide. The tomatoes are sweet and very tasty.
By bringing the plants inside the greenhouse you can extend their growing season by month or until the green fruit on them ripens. If the plant does produce more blooms you can always try the pollinate them yourself with an artist brush going bloom to bloom like bees would do. The pepper plants can also be dug and moved inside. Plants brought
into the greenhouse should be inspected for insects and disease. You do not want to introduce these problems into the greenhouse.
Most retail green houses, markets and the box stores pull their seed packs in August if not before making room for fall plants. If you have waited you may have to purchase seed from all those seed catalogs you have been receiving. Shipping charges can add greatly to your order, for that reason it is generally better to purchase from only one seed catalog company.
Growing winter herbs provides a good variety of plants available usually in 4-inch pots or from seed. Locally we have one greenhouse, Ashcombes Farm and Greenhouse, that have a very large variety of potted herbs available almost all winter. In general, leafy greens and root crops (herbs, lettuce, greens, beets, carrots, and radishes) do better than those grown for their fruit (tomato, peppers, and cucumbers). Varieties bred specifically for the short days and cool temperatures of winter perform better under these conditions.
One of the biggest growing problems in the winter months is the soil. Use soil containing plenty of perlite which will provide good drainage for the plant’s root system. Compacted soil will hold too much water and root systems may rot. The use of manure and other compost should be well-aged to minimize disease and salt toxicity.
Leaf compost from the local township piles is not a recommendation from me. Leaves and even grass cuttings dropped off at township sites usually contain a variety of chemicals sprayed on lawns. In late fall with the first snows the collected leaves contain road salts used to melt snow and ice. Township compost can be good for the outside gardens when worked into the soil but not necessarily for potted plants. Your winter grown vegetables and herbs will need some light fertilizing. Do not overdo it on the mixture. Half strength should be tried first and if needed increase the strength of the mix. Water soluble fertilizers are readily available to the plant and easy to regulate. Fish emulsion and liquid seaweed are excellent for winter vegetables. You can use a complete fertilizer like 15-15-15 of one that it tailored to your specific crop. In the dark short days of winter, the plants will not require as much fertilizing, or none if prolonged cloudy days persist.
Ventilation and good air circulation within the greenhouse are vital to minimize disease and insect problems and to maintain a constant supply of carbon dioxide necessary for plant growth. On good sunny days when the greenhouse temperature climbs open some vents or the door to allow fresh air to enter. Just remember to close them in the evening. For this reason, electric temperature controlled intake vents or the use of solar controllers on intake vents works quite well for exchanging air within the greenhouse.
Speaking of solar vents, if the greenhouse is closed in the winter months disconnect the opening rod from the controller cylinder or the adjusting thumb nut from the
controller itself. This is important if the vent is locked in position on its frame. On sunny days the controller will try to push open the vent and may damage the vent or may cause the cylinder to blow its seal rendering the opener somewhat useless. New cylinders are however available from the manufacture just for this reason.
Vegetables can be grown in raised or inground beds, in containers, there is no ending to what they can be grown in. Just remember that inground beds are the best since they will help keep the roots warmer. Pots on benches will have soil temperature equal to the surrounding air temperature in the greenhouse. Several thermometers positioned around the greenhouse are essential for knowing the temperature. Winter grown vegetables usually do not have the root masses those grown outside in the summer garden.
Beets, carrots, radish, and turnips tolerate a cool greenhouse and require only about 6 to 8 inches of soil. Research your seed catalogs for short varieties. Broccoli, Brussel Sprouts and Cauliflower need more depth because of their long tap roots, usually some 10 to 12 inches deep. There are apparently miniature varieties available on the market. Do not be afraid to experiment in the greenhouse. Seeds are pretty cheap and down to fifty cents a pack some in stores in the fall months. Keep your seed stored in dry average room temperatures. Most seed do not like freezing temperatures and moisture. And remember that the garage and basement are generally the worst places to store seed.
Tom Eckert is the Director of Publication
and Editor for the HGA.