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Dundee Fact Sheets

Tomatoes                                                    Print This Sheet



Either start tomato plants from seed indoors in early April or buy transplants in the spring. Tomato plants need warmth and should not be set outside until about June 1. Add peat moss, manure, lime, and a balanced fertilizer such as Gardener’s Special or Myke’s for Vegetables, to the soil. Weak or top-heavy seedlings should be planted extra deep, allowing the stem to send out extra roots to better anchor the plant. If your seedlings are in peat pots, peel away the pot bottoms and any part of the sides that extend above ground level. Feed with one of the same fertilizers every 3 weeks starting when the fruit is golf ball size. Avoid high nitrogen fertilizers.


In general, tomato rows should be 36” - 48” apart. Plant 24” - 36” apart in the rows for staked tomatoes and 36” - 48” apart in the rows for plants that are allowed to sprawl on the ground (fruit injury may occur with this method - use mulch to protect the fruit.) Unstaked tomatoes mature later but need no pruning and are less apt to develop problems associated with sun injury.


A staked tomato method involves placing a sturdy 8’ cedar post at either end of the row and connecting them with heavy wire across the top and also 6” from the ground. Tie heavy string to the wires at each plant location. Train the vines to grow up these strings, pruning out side branches to leave one strong stem. This method gives you clean fruit and an earlier yield. Another method involves individually staking the plants. Train the plant to a single stem. Remove suckers (shoots between the leaf branches and main stem) past where they’ve developed two leaves. These few leaves will provide some foliage to protect the fruit from sunscald. Another method uses wire tomato cages. Securely stake the cages so they don’t topple. This method involves little pruning - just remove what grows over the top - and provides a large, late-maturing yield.


Some varieties set fruit in a very narrow temperature range - night temperatures of 55 - 75 degrees. If these temperatures do not occur, blossoms will drop. There is about a 50 hour threshold when blossoms either set fruit or drop. Early season varieties set fruit at lower temperatures. To improve fruit set, try using a fruit set product or very gently shake the plants on bright sunny days to increase pollen activity.


Cutworms hide in the soil during the day and feed at night, cutting the plant off at soil level. Use a cutworm collar at planting time. These collars can be made from cardboard or foil. Push them down into the soil 1” and keep them about 2” - 3” away from the stem. They should extend at least 2” above the soil. Bonide’s Eight will also control cutworms. Hornworms are 4” green worms with a rear horn. They eat foliage and fruit and should be picked off. Flea Beetles are small jumping beetles that eat foliage and give it a buckshot appearance. Hornworms and Flea Beetles can be controlled with Eight. Nematodes damage roots and cause wilted, stunted plants. Control by planting resistant varieties (”N” will appear on the label.)


Fungal and viral diseases also target tomatoes. Early Blight causes dark brown, irregular spots on fruit and leaves and is worst during hot, humid weather. Spray every 7 - 10 days with Maneb or Captan. Late Blight causes water-soaked dark spots on leaves and fruit. White fungus may appear on leaf undersides. The leaves wilt and brown. Fruit develops an orange peel texture. Spray as above. Fusarium Wilt yellows the lower leaves (sometimes just on one side) and continues up the plant. Stems have a dark brown color on the inside. Verticillium Wilt causes older leaves to yellow, shoots to wilt, and defoliation. Use “F” or “V” resistant varieties and remove any plants that develop symptoms of these wilt diseases.

Fruit Crack occurs when heavy rain is followed by bright, hot sun. This is especially a problem on staked plants that don’t have enough sun-shielding foliage. Keep the plants evenly moist and, if you prune, leave enough foliage to shade the fruit. Blossom End Rot causes fruit to develop black, watery depressions on the bottom. Prevent this by providing even moisture, 3” - 6” of mulch, low nitrogen fertilizer, a soil pH of about 7.0, and adequate calcium. Yield boosting products may also be purchased.


Harvest when fruit pulls easily from the vine. As the season winds down, pinch off vine tips and flowers to hasten ripening of green fruit. If you still have green, unblemished fruit at frost time, ripen it in the dark at about 45 - 50 degrees with a ripe apple in a paper bag.



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