Ground Mulch, Row Covers, and Staking
Ground Mulch and Row Covers
The use of black plastic ground mulch is recommended to control weeds in the row and conserve water. Plastic mulch may also raise soil temperatures in spring to promote an earlier harvest. In order for black plastic to raise the soil temperature, there must be good contact with the soil beneath. New plastic films called IRT (infrared-transmitting) provide more soil warming with similar weed control, but are more expensive. Red plastic mulch does not raise soil temperature as much as black plastic, but has been reported to improve yield specifically for tomato up to 20% compared to black plastic. However, results are inconsistent between field studies, possibly due to variation in plastic quality (Orzolek and Otjen). Cover crop mulches and other organic mulches can also be beneficial. For more information on mulches, reference the online University of California Davis Publication 8129 “Mulches in California Vegetable Crop Production.”
Row covers provide a windbreak that helps protect plants from frost, and can enhance yield and earliness. Spun-bonded row covers (such as Reemay) made of lightweight polyester or polypropylene can rest directly on top of plants, but edges should be secured. Plastic row covers trap more heat during the day than spun-bonded covers, enhancing plant growth and earliness, but they overheat more quickly and require careful monitoring. Perforated plastics are available to provide some ventilation while retaining heat. Plastic covers should be supported by heavy wire or other secure support to keep plastic from contacting plants. Spun-bonded and plastic row covers should be removed as plants outgrow the cover, if plants begin to flower, or when temperatures under the cover regularly exceed 90°F.
Spun-bonded row covers (left) and perforated plastic row covers (right).
The stringing tool extends the worker's reach and helps to keep the twine tight.
Support for eggplant, pepper, and tomato is not required, but offers a number of advantages. Fruits grown on staked and pruned plants can mature earlier, and are cleaner and easier to pick. However, extra labor is needed for pruning and tying. Determinate tomatoes are commonly trellised using the stake and weave system (Fig. 9.5). It involves driving 4 foot long wooden stakes 18 in. deep between every other plant and weaving string horizontally between the stakes.
Fig. 9.5. Fruits grown on staked plants mature earlier
Prior to applying the first string, suckers (secondary shoots) are removed. Suckers are the vigorous new growth found at the base of the leaves. Remove suckers from the bottom three leaves on determinate varieties when the suckers are 3 to 4 inches long. Suckering reduces vine growth, but promotes earlier and larger fruit. After suckering, attach the first string one foot above the ground and add additional strings after every 8 to 12 inches of new growth. Generally, plants are suckered once and tied three to four times.
The most common method of trellising indeterminate varieties is a vertical wire system. Six foot tall support posts are placed every 5 to 10 feet with a 12-guage wire running between them. Plants are then tied to a vertical piece of twine attached to the overhead wire. Plants are twisted around the twine and suckered regularly to control growth. Additional ties and/or clips are used to keep the vine attached to the twine.