Setting Out Tomatoes Early

May 1, 2015

Setting Out Tomatoes Early

Gardeners often try to get a jump on the season, and bragging rights for producing the first home grown tomato, by planting tomatoes as early as possible. Though this can be successful, there are certain precautions that should be observed, especially this year with the cooler than normal spring.

Adequate soil temperature: Tomato roots do not do well until soil temperatures reach a fairly consistent 55 degrees F. Use a soil thermometer to check the temperature at 2 inches deep during the late morning to get a good average temperature for the day. Soil temperatures in our area just reached and maintained this level in the last week of April

Harden off plants: Plants moved directly from a warm, moist greenhouse to the more exposed and cooler conditions outside may undergo transplant shock. Transplant shock causes plants to stop growing for a time. Plants can be acclimated to outside conditions by placing them outdoors in a location protected from wind and full sunlight for a few days before transplanting.

Another way to harden off plants is to transplant them and place a cardboard tent or wooden shingle to protect them from wind and sun for 2 to 3 days. The best conditions for transplanting is an overcast, still day.

Protection from frost: Tomatoes cannot tolerate frost. The average last frost in Burt County is April 30, but watch the weather and cover the plants if frost threatens. A floating row cover or light sheets can be used for protection. Actually a floating row cover can be left on the plants for two to three weeks to increase the rate of growth and establishment.

Other tips for getting tomato plants off to a fast start include:

1.  Use small, stocky, dark green plants rather than tall, spindly ones. Smaller plants form roots rapidly and become established more quickly than those that are overgrown.

2.  Though tomatoes can be planted slightly deeper than the cell-pack, do not bury the plant deeply or lay the stem sideways unless the plant is very leggy. Though roots will form on the stems of tomatoes, this requires energy that would be better used for establishment and growth.

3.  When planting in soils with high nutrient values, some or all of the fertilizer may be omitted at planting. If soil nutrients are low, incorporate 2 to 3 pounds of a complete fertilizer, such as a 10-10-10, per 100 square feet of garden area when preparing the soil. Do not fertilize again until the first fruit is about the size of a half-dollar. Then scatter one teaspoon of a complete fertilizer around each plant, about 8 to 10 inches from the stem, and water  it in thoroughly to move the fertilizer through any mulch and into the soil. Repeat this once or twice a month through the rest of the season. Do not over-fertilize. Excessive nitrogen fertilizer tends to force plants to produce lots of dark green foliage, but the healthy looking plant won't set fruit.

4.  Always water tomato plants around the base of the plant rather than using an overhead sprinkler. This will reduce, but not eliminate, the likelihood of several diseases developing on the plants.

5.  Finally, do not mulch until the plant is growing well. Mulching too early prevents soil from warming up. A course mulch like straw or wood chips will allow water to pass through it and will not matt down and shed water away from the plant like grass clippings can.

For more information on growing tomatoes, contact your local Nebraska Extension office for a copy of the NebGuide, Tomatoes in the Home Garden, or get a copy of it online at