Washington State University Extension

Garden Tips

Tomato Transplants and Planting

GARDEN TIPS – written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA April 23, 2015

Here I go again talking about tomatoes, but since they are the favorite veggie crop of home gardeners I am hoping you will forgive me. This time, let’s talk about tomato transplants and how to plant them.

Horticulturists will tell you when purchasing tomato transplants select ones that are only six to eight inches tall with a strong main stem (about the same diameter as a pencil). Avoid plants that are leggy, yellowish-green, much too big for their pots, already flowering, or infested with insects. Also, avoid plants that have grown too large in the greenhouse and been cut back to disguise this.

A healthy, stocky transplant is the ideal, but many gardeners who grow their own transplants from seed end up with leggy plants. This is because the plants were either started too early, not provided with enough light, or both!

Leggy tomato stems are weak and often can not support the top of the plant, especially in windy weather. To remedy the situation, gardeners should bury the stem and the roots when planting. This is best accomplished by creating a shallow 4 to 5 inch deep trench, removing the leaves from the bottom 2/3 of the stem, laying the transplant on its side in the trench, and then covering the roots and stem with soil. Leave the remaining leaves several sets of leaves above the soil.

Roots will form along the buried stem, resulting in a stronger plant. The leaves and stems left above the soil will naturally turn and start growing upwards. Before planting, remove the pot including peat or other biodegradable pots, and gently then loosen the roots.

When purchased at the nursery, transplants have usually already been “hardened-off” by exposure to wind and sunlight and by receiving less water and fertilizer than they were getting in a greenhouse. To get them ready for the “real world,” homegrown transplants started indoors will need to be hardened-off  by gradually introducing them to outdoor conditions. This is done by placing them outdoors in the sun for couple of hours and then increasing the amount of time outdoors each day for about a week, but bringing them indoors at night.

Tomatoes are frost-sensitive, warm season plants. They prefer warm weather and warm soils. There is no advantage to planting them early and protecting them from frosty nights. If you are into easy gardening with no extra work, plant your tomatoes no earlier than May 1st, the average date of our last spring frost for most of the region. However, tomato plants will not grow much until the soil warms to at least 600 F and prevailing daytime temperatures are above 700 and nighttime temperatures are above 600.

If you yearn to plant your tomatoes early, you can create a “mini-solar greenhouse” for each with Wall-of-Water or Kozy Coat garden teepees. Garden teepees are 12″ diameter cylindrical garden devices made of channeled clear or tinted plastic sheeting. The channels are filled with water and then the teepee is set over a plant. The water absorbs heat during the day, keeping the plant warmer than the surrounding air during the night and day and helping warm the soil.

When teepees are tilted inwards at the top of the cylinder early in the season, they can provide considerable protection from frost, down to 160 F according to the manufacturer. They also protect plants from wind. Teepees should be removed when temperatures reach 80 to 85 degrees, otherwise they “cook” the plants.

May 1st is just a week away so start getting ready for planting tomatoes, but wait until the soil and temperatures are warm enough.

Garden Tips, WSU Extension, Benton County, 5600-E West Canal Drive, Kennewick, WA 99336-1387, 509-735-3551, Contact Us

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