Few books on hydroponics deal with the idea of moving a soilless garden outside. To my way of thinking, though, the whole point of hydroponics is to get the best possible year-round results. There is a great temptation for the home grower to lean back and say, "Outdoor gardening? Who needs it? I'm going to keep my garden in the basement all year. No wind, no bugs, no problems." It really isn't necessary to move your garden outdoors in summer, but if you don't, you'll be missing the opportunity to grow plants of tremendous proportions and yield. It is possible, for example, to root ten to twelve staking tomato vines in a single sixteen by twenty-four inch planter outdoors, spread them on a six foot wide trellis and let them grow to heights of seven to nine feet. There is ample nutrient in the planter for all and ample light from the sun. This is how to get yields often to twenty pounds per plant from each crop, much higher than indoors. If you are truly interested in results, it seems foolish to me not to go outdoors in summer.
Moving your garden outdoors takes planning, however, because you have to make your unit portable, and you have to know when the first frost-free day in your area is likely to be. When building or buying a hydroponic garden, it is a good idea to be on the lookout for such things as tea caddies with wheels or a small wheelbarrow. These can make transportation much easier.
The first frost-free day is a red letter one for soil gardeners. It's the date when all chance of (overnight) ground frost has passed. In the northern United States and most of Canada's southern belt, this is May 24th. The local Agricultural Office publishes this information for specific geographical areas. With a portable hydroponic unit, your outdoor growing season can start three to four weeks earlier than this date, because you have no ground frost to worry about. On a protected porch or balcony, you can take advantage of the heat given off by the building. However, if you simply take your plants outside in April or May and leave them there, you will probably kill them. Plants need to be "hardened off." That is, they have to become gradually accustomed to the cooler temperatures and higher light levels of an outdoor environment. This is done by moving them out for an hour or two during the warmest part of the day and increasing the time an hour or two every few days until they are able to withstand twenty-four hours a day outside. The entire hardening off process should take about a week or two.
For the first, early month of outdoor hydroponic gardening, it is still a good idea to listen closely to weather reports. When a freak frost is announced, cover your plants and planters with paper or plastic overnight. When the overnight low is announced as 32°F (0°C), it will still be about 37°F (+3°C) in your protected location. A low of 26°F (— 3°C) means it's a good idea to move your plants back indoors for the night. In any case, be sure to set your plants in a protected spot with a southern or western exposure if possible.
Two months before the first frost-free day plant your seeds indoors under lights. Big plants are particularly suited for outdoor hydroponics, especially types that grow too tall or range too far for efficient indoor lighting. Staking tomatoes, pole beans, green peppers and cucumbers all do exceptionally well. If you are buying seedlings from a commercial grower rather than raising your own, select only the best. They should be dark green, medium tall and heavy stemmed. (Don't forget to remove all of the soil from the roots of any plants you purchase.) Leggy plants, either bought or raised, should be planted as deeply as possible, up to the first or second set of true leaves. Newly planted seedlings should be protected from direct sunlight for the first few days, so they don't get burned. Plant sunburn appears as whitish, leached-out leaves.
If you time the seeding and moving of your unit correctly you should have red, ripe tomatoes in June, long before soil gardeners, and lettuce, beans and peas even earlier. If you don't want to cut it quite that fine, allow an extra week or two after the first frost-free day.
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