Tips on Transplanting Tomatoes
As the weather warms up, gardeners are very eager to get those tomato transplants into the vegetable garden. Whether you are transplanting your own carefully tended seedlings or purchased plants, some advance planning will move you a long way toward a successful tomato growing season.
Planning Your Garden
- Design a plan by plotting out your garden space on paper or using an online garden planner. If using an existing vegetable garden space, don’t plan to put tomato plants (or other plants in the same plant family) in the same space year after year. Tomatoes are in the nightshade family along with potatoes, eggplants, and peppers.
- Select an appropriate site with 6-8 hours of sun; healthy, well-drained soil; an accessible water source; good air circulation; and protection from the wind. Get a soil test every 3-4 years, so you can amend the soil appropriately before planting. Tomatoes do best in a pH between 6.0 and 6.8.
- Know your Plant Hardiness Zone and determine when it is safe to transplant tomatoes, which should be after the last average frost dates for the zone and when the soil has warmed. If nights drop toward 32ºF after planting, protect the transplants with row covers, cloches or other means.
- If planting seedlings, it is important to acclimate them to the outdoor environment by hardening them off before transplanting. Decrease watering and stop fertilization 2 weeks before transplanting, and then expose seedlings gradually to filtered sun, then direct sun, light wind, and varying temperatures over 5-7 days.
- Buy healthy looking plants with no spindly stems, yellowed leaves, flowers or other signs of insects or disease. Feel free to take plants out of their pots and inspect the roots before purchase.
- Make sure seedlings and purchased plants are 6-10 inches tall before they are transplanted.
Planting with Care
- Space transplants 36 inches apart with 36 inches between rows, if using stakes or cages. If trellises are used, plan for 24 inches between rows.
- Try horizontal planting by digging a shallow trench, then laying the plants diagonally so that only 2-3 sets of leaves are above ground. This promotes more root growth and makes plants healthier. Healthy plants are less susceptible to plant diseases and pests.
- After planting, water deeply at the base of the plant. Water early in the morning, if possible. Tomatoes need between 1-2 inches of water per week depending on the weather conditions.
- Be sure to fertilize with about one pint of a starter solution or dilute fish emulsion around each transplant. Side-dress with fertilizer (such as 5-10-5) 1-2 weeks after the first tomatoes begin to develop, then after the first ripe tomato and one month later.
- Tomatoes should be staked, caged or trellised to keep plants off the ground, prevent fruit rot, promote air circulation and make harvesting easier. Be sure that you can put your hand through the mesh of tomato cages to allow easy access to plants for weeding, pruning and harvest.
- Decide whether to prune or not. If you do prune staked or trellised tomatoes, do so to select 1-2 main stems. Only pruned caged tomatoes only once, if at all, leaving 3-4 main stems. Pruning is controversial. It can promote earlier harvest, prolong harvest, produce larger fruits and reduce disease. However, it can reduce yield and make plants more susceptible to sunscald.
- Don’t forget to mulch to keep soil moist, control weeds and prevent disease. Good mulches for tomatoes: compost, shredded leaves, shredded wood mulch, red plastic or dark landscape cloth.
Preventing Diseases and Harmful Insects
Consider these strategies to help maintain your garden and keep your plants healthy:
- Companion planting is cultivation of plants close by that enhance each other’s growth or protect each other from pests. Companion plants for tomatoes include nasturtium, marigold, asparagus, carrot, onion, parsley, basil, cucumber, and bee balm. Avoid plants that are incompatible with tomatoes, such as Irish potatoes, fennel, cabbage, corn, or dill.
- Cover crops are planted in the space between plants and rows to add nutrients and organic matter to the soil, loosen and stabilize the soil, control weeds, and attract pollinators. For warm weather crops like tomatoes, your options include buckwheat, soybeans and crowder peas.
- Crop rotation is one of the most important practices. Plants take nutrients out of the soil; rotation replenishes nutrients to the soil. Move tomatoes around in your garden (just a few feet will do) and don’t plant where you’ve planted any nightshade family plants recently.
Remember that prevention is much better than confronting a disease or pest when it becomes established in your garden. Cultural best management practices can help avoid problems before they arise. Set yourself up for success:
- choose disease-resistant seeds and plants
- plant at recommended times
- maintain healthy soil with the proper pH and good drainage
- provide adequate water and fertilization
- clean and disinfect tools
- control weeds and remove diseased plants promptly and plant debris at the end of the season
- “scout” for troublesome insects on a regular basis, and destroy them by picking them off your plants before they do major damage
- use caution with biological or chemical controls; consult the 2021 Pest Management Guide for recommendations.
Lastly, encourage the beneficial insect population by increasing the numbers and diversity of pollinator-attracting plants in and around your garden. Most insects are not harmful, and more beneficial insects will mean more insect predators of pests that can damage your plants and transmit disease.
Following these commonsense guidelines can help you avoid many of the problems that tomato gardeners encounter and help your tomatoes thrive. Here’s to an abundant harvest of tasty tomatoes!
Prepared by Extension Master Gardener Bev Thierwechter, who led a virtual Garden Basics class on tomatoes and tomato diseases on May 15.
“Heirloom Tomatoes,” Cleve Campbell, The Garden Shed, April 2016, Vol. 2, No. 4.
“Planning the Vegetable Garden,” Alex X. Niemiera & John Freeborn, Virginia Cooperative Extension, Virginia Tech, Publication 426-312, 2015.
“Tomatoes,” Diane Relf et al., Virginia Cooperative Extension, Virginia Tech, Publication 426-418, 2016.
“Tomato Diseases,” Cleve Campbell, The Garden Shed, June 2015, Vol. 1, No, 6.