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Growing vine-ripened tomatoes in a solar/composting greenhouse.

If this is the first season in your solar/composting greenhouse, start your seedlings the first week of November. By January first, most northern solar/composting greenhouses can provide the proper soil temperature. In the South, greenhouse growers can sow tomatoes at a much earlier date.

Choose your favorite organic potting soil mix. Make sure it is lightweight and can hold moisture well. Completely fill your flats with potting soil. After it has been moistened, the soil line will fall a little. Make rows or small furrows a quarter inch deep. Press tomato seeds into the rows with 1/8-inch between each seed. Close up the rows, cover the seeds and gently firm the soil. Mist or lightly water the soil, nestling the seeds into their nursery beds. Place the seed flats in a warm area with temperatures between 65 [degrees] and 70 [degrees] F.

In December, short days and long nights create unfavorable conditions for tomato growth. Natural daylight at this time is 12 hours or less, whereas tomato seedlings grow best with 16 hours, or more, of light. To avoid producing weak, pale green, leggy seedlings, we use grow lights.

When your tomato plants are three to six inches tall, it's time to transplant them into larger containers. We prefer to use four-inch biodegradable peat pots. Both plant and pot can be transplanted into the greenhouse beds without risk of shock.

After four or five weeks of growing in the peat pots, plants should reach transplanting size. Stems should be thick and leaves dark green in color. Flower buds have not yet developed. If your plants must wait longer in their growing containers, fertilize with organic soluble nutrients. Compost tea or fish/seaweed emulsion are good. We often spray our tomatoes with Kelp Plus, a fish/seaweed extract.

Tomatoes are heavy feeders and need plenty of nutrients. They thrive in a soil with a pH range of 6.0 to 6.5. This range is more acidic than the range other vegetables prefer. Potassium is a key nutrient and essential for abundant fruit production. Compost enriched with wood ash or greensand can boost the potassium (K) content in your soil. Using large amounts of wood ash raises the pH, so use with caution. Adequate calcium (Ca) prevents problems with blossom end rot (a large, dry, black or brown sunken area that appears at the bottom of the tomato fruit). We've always found well-made compost the best soil builder and nutrient source for tomato culture.

After the greenhouse tomato beds have been prepared, soil temperatures are warm (55 [degrees] F and higher) and your trellis system is made, set out the young plants. Trellising can be creative. I've seen them made of wire, fence, steel rods, bamboo and wooden stakes. They need not take up too much space, but they must be strong. One tomato plant can weigh 15 pounds or more. Building a trellis and pruning allows closer planting.

Trellised tomato plants may be set out 18 inches apart, with three feet or so between each row. It's best to transplant on cloudy days or late afternoon when the sun is going down. Water with fish/seaweed mix. If it is very hot in the greenhouse, you may want to provide shade for the first five days. Best growing temperatures are 80 [degrees] F during sunny days and 68 [degrees] F at night. Cloudy days bring diffuse light, and the greenhouse can be kept at 70 [degrees] during daylight.

Water and fertilization are critical. An even supply of water throughout the growing period will help minimize problems. Use drip-irrigation, keep the soil moist, but be cautious about over-doing it. Pale green leaf tissue or stem rot can be symptoms of over-watering. Water in the morning to reduce evaporation losses and to minimize humidity problems.

As growing progresses, the plant metabolism speeds up. Organic matter decomposes at a faster rate, and tomatoes appreciate a foliar spraying of fish/seaweed (Kelp Plus) every three or four weeks.

During flowering, pollination and fruit set can be assisted by gently shaking the tomato plants for five minutes at the middle of the day. Pollen drops down and reaches the pistil of each flower bud. If your greenhouse is large enough, you can set up mini-bee hives for pollination.

Prevent any crop losses or insect damage by keeping on the look-out for potential problems. The most common diseases associated with greenhouse tomatoes are damping off, botrytis, blossom drop and greenback. Damping off is a fungal disease which attacks young seedlings. Often the fungus is introduced via contaminated seeding mix, a good reason to use fresh potting soil rather than an old mixture. If young seedlings have toppled over and the stem is brown and depressed at the soil line, the cause of death is damping off.

There are two other common fungal diseases favored by high humidity and poor ventilation. Botrytis is seen as a gray mold that attacks leaf and stem tissue. Cladiosporum fulvum is a fungus that flourishes in cool greenhouses where the relative humidity is above 80 percent. Leaves turn yellow-brown, and then grayish spores cover the leaf surface. We use disease suppressive organisms to control these and other fungus diseases.

Blossom drop and greenback have other causes. Occasionally, if the spring crop has been set out a few weeks too early, blossoms on the first flower truss may fall off. Cool night temperatures which fall below 55 [degrees] F are responsible. Greenback is a common problem in tomato fruit. Fruits will ripen unevenly with the top portion remaining green while the bottom half is red and ripe.

Trellising tomatoes is tricky and takes time. But the bounty of off-season tomatoes repays the effort. Training the vines requires the regular pruning of suckers and old leaves. Pinching off side shoots eliminates extra growth which can shade ripening fruit. Pinching helps to channel all the plant's energy into one main stem, enhancing fruit production.

Unwanted suckers develop where the leaf petiole meets the main trunk. They grow very fast and can soon reach the same size as the main stem. You'll need to pinch off side shoots at the junction when they're three to four inches long.

Layering and double-leading are two tomato training methods. They can increase your yield over the growing season. Layering is a technique used with a trellis. In this system, tomatoes are kept below 6-1/2 feet tall so that all trimming, training and picking is within easy reach. At planting time, dig a four-to-five inch deep trench alongside the trellis. Then take your tomato transplant and prune off the lower leaves. Place each plant horizontally in the trench with the tip growth near the surface. Cover the roots and stem with two or three inches of soil, then press it down.

This method causes new roots to form along the buried stem. The young stem will grow thicker, enlarging the transport system for nutrients and water. Because the first eight to ten inches of stem is buried in the soil, the first cluster of fruit will form close to the ground. And, at the end of the season, you should have one or two bonus flower trusses.

In the double-leading method, one vigorous sucker is selected and trained into a second stem. Professional growers prefer the sucker below the first flower truss on each tomato plant. All remaining side shoots are pinched off. If by chance this sucker is accidentally snipped off, the second or third side shoots can be a substitute. Eventually, the double-stemmed tomato will have a V-shaped joint in the trunk. Be sure to give both stems of each plant a string or stake so the branches don't split. With both layering and double-leading systems, set out your tomato plants 18 inches apart with three feet between rows.

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Copyright 1999 Gale, Cengage Learning. All rights reserved.

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Publication:Countryside & Small Stock Journal
Geographic Code:1USA
Date:Nov 1, 1999
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