Using Transplants in the Garden

Introduction

To have a productive garden, transplants are used for many common vegetables, such as tomatoes, peppers, broccoli, Brussels sprouts, cabbage, cauliflower, cantaloupe, cucumbers, lettuce, squash and watermelons. While some of these crops might also grow from direct seeding, there are several advantages to using transplants. Transplants will accelerate early harvest and result in a uniform yield. Using transplants reduces labor for thinning and ultimately saves seed costs. Losses from poor seed germination can be eliminated. Transplants also can replace harvested crops quickly when doing succession planting.

New gardeners might not start out growing their own transplants, but as skills and knowledge grow, there are even more advantages to producing your own transplants. The availability of the specific cultivar desired is ensured. Fewer insects and diseases are introduced to a garden from homegrown transplants. The home gardener can choose their containers and type. Additionally, many gardeners get personal satisfaction from germinating and growing their own transplants.

Most gardeners will purchase transplants for the home garden at some point. As a new gardener, buying transplants is usually the easiest and most successful option to start out. As gardening experience grows, selecting which crops to direct sow or establish as transplants will become more apparent. Regardless of which method is used in the home garden, high quality plants come from high quality, disease-free seed.

Seeds

Seed packets should state the year for planting. If it is not the current year, it might not germinate well and seedling vigor may be reduced. Stored seed can be tested for germination before planting. Roll some seeds in a damp paper towel and place it in a plastic or glass container with a tight-fitting lid. Place the container at room temperature for a week to 10 days, then count the number of seeds that have germinated. The paper towel must remain damp the entire time. Determine the germination percentage by dividing the number of seeds that sprouted by the total number of seeds tested, and then multiplying by 100. If, for example, you tested 10 seeds and seven sprouted, then the germination percentage is seven divided by 10, times 100, which equals 70%. This exercise will help estimate how many transplants or plants can be grown and how many transplants will need to be purchased.

Hardening Transplants

Plants started indoors or purchased at a greenhouse should be “hardened” or acclimated to the outdoors before being transplanted to the garden. Set the transplants in a shady, protected outdoor location about seven to 10 days before planting if this is their first time outdoors. Warm season vegetables, such as tomatoes and peppers, should not be exposed to temperatures below 55 F. Gradually expose the plants to longer periods of sun over several days. Also, allow the plants to dry slightly between each watering during the hardening period. Hardening young seedlings increases their food reserves, reduces the severity of transplant shock and increases the chance of survival in the garden.

For more information on starting transplants, see our Vegetable Transplant Production publication.

Purchasing Transplants

Some considerations are key when purchasing transplants from garden centers and greenhouses. The main rule is to be selective. Look for healthy transplants – short, stocky plants with short internodes, a thick stem, free of diseases or insects, uniform, dark green leaves, and white roots with vigorous growth, but not so much so that they wrap around the soil medium. Roots encircling the outside of the soil are searching for water and nutrients. This could be due to a lack of water or a lack of nutrients. It is a first sign of stress, indicating that they have outgrown their container and used up all the nutrients. Select dark green, stocky plants over yellow, spindly ones. Seek transplants that are as wide or wider than they are tall. They should be free of leaf spots, yellowing and dying leaves. Extremely large transplants are more likely to suffer transplanting shock and to grow slowly, bolt or even to die than transplants of the proper size and age.

Local nurseries grow many of their transplants from seed. This will often provide the best quality plants and varieties for your region. If purchasing from a garden center, observe the conditions in which the plants are raised. Are workers attentive to the plants’ needs?  Feel the soil – is it moist or dried out? Even one day of inadequate water can stunt a plant. Neglect doesn’t always equate failure, but observations are important in shopping for healthy transplants.

Purchase transplants at the right time of year. If bought too early or planted before weather conditions allow, plants will suffer stunted growth and could even die. If bought too late in the year, transplants many have a harder time acclimating to the new environment in the garden or growing well.

Buy transplants no more than a day or two prior to planting. It’s always best to plant within the same day of purchase. If this isn’t possible, keep them watered and in a shaded location until you can plant them in the ground.

Research the transplants before buying. The best success is found when planting what is planned. Plant tags have basic planting instructions. Become familiar with popular varieties sold and grown in the area. Refer to variety recommendations provided by WVU Extension in the annual garden calendar.

Don’t choose plants with fruit or flowers. Vegetables that start forming flowers could be under stress. The stress causes them to want to reproduce seeds as quickly as possible. But this isn’t always the case. Sometimes they’ve just been growing so long it’s time for them to produce fruit. Either way, if given a choice, select plants without these flowers. Transplants will need that stored energy to acclimate to the garden – expanding its roots and growing more leaves – not producing fruit. If choosing a transplant with flowers, pinch them off to allow its energy transfer to acclimation prior to setting new flowers or fruit.

Know how to identify problem plants. Make sure the leaves aren’t wilted, curled or spotted. This could indicate a disease, which not only could affect that plant but also your entire garden.

Check for bugs on transplants to ensure that no new insect pests are transported and introduced to the home garden.

Skip the clearance aisle at the garden center. Transplants in the clearance aisle have outlived their stay in a pot and have a greater likelihood of being in distress. They are more likely to struggle when transplanted and not produce as good of a harvest as their healthier counterparts. Experienced gardeners may be able to meet the challenges these transplants could present.

Setting Transplants Into the Garden

The main goal in transplanting is to avoid root disturbance as much as possible. Little damage occurs with biodegradable pots, like peat pots, but such containers must be planted below the soil’s surface. Any portion of the peat pot remaining above the soil surface should be removed because it acts as a wick and draws moisture from the soil around the transplant on windy days.

Carefully remove plants from plastic cell packs by gently squeezing the bottom of each compartment. Remove plants in plastic pots by tipping them on their sides and tapping the bottom of the pots. With flats of young seedlings, use a sharp knife to cut the soil into blocks around the plants one or two days before you plan to transplant. Water the blocks thoroughly after cutting. This will stimulate the plants to produce tiny root hairs, thus lessening transplant shock.

Popular vegetables, such as tomatoes, can be planted fairly deep. Remove some of the lower leaves on the transplant and plant deeper than the root ball to include some of the stem. Roots will form from the stem and expand the root zone of the tomato plant.

If possible, set plants into the garden in the late afternoon to evening or on a cloudy day. This will allow them to begin recovering from transplanting shock before exposure to the hot sun. Early plantings may need protection, such as plastic covers or cloches, to avoid damage from frost. When coverings are used, be sure to provide some ventilation so young plants are not damaged by very high temperatures.

Fertilizing Transplants

For best growth, give each plant 1 to 2 cups of a starter fertilizer solution immediately after setting it in the ground. A starter fertilizer solution can be prepared by following directions on a water-soluble fertilizer or by dissolving 1 to 2 tablespoons of an all-purpose garden fertilizer, such as 20-20-20, in 1 gallon of water. This is one time when more is not better. Fertilizer burn damage can result if too much fertilizer is used.

Warm and Cool Season Crops

Crops are generally classified as warm or cool season. Cool-season crops are hardy or frost-tolerant. Warm-season crops are not frost-tolerant and must be transplanted after the last frost of the season. Consult the WVU Extension Garden Calendar for specific planting dates. Cool-season vegetables include many popular vegetables, such as beets, broccoli, cabbage, lettuce, kale, cauliflower, kohlrabi, leeks, onions, peas, spinach, radish, etc. Many cool-season vegetables can be grown in the spring and fall in West Virginia. Depending on location within the state and whether season extension tools (e.g., row covers, low tunnels or high tunnels) are used, most cool-season vegetable crops are transplanted two to six weeks before the last spring frost. For fall production, cool-season vegetables are transplanted four to eight weeks before the first fall frost.

To determine how late to plant in the fall in your region, there is a simple formula used by growers: Number of days from seeding to harvest + average harvest period + fall factor (estimated at two weeks) + frost sensitivity.  

So, for example, cucumbers are 55 days from seeding to harvest + 21 days of harvest + 14 days for the lower light/temps of fall + 14-day frost buffer = seeding 104 days before the first frost date (October 15), which would be approximately July 1.

Warm-season crops transplanted before the frost-free date require row covers, hot caps or low tunnels to prevent damage to the plants. Warm-season vegetables include crops, such as beans, tomatoes, melons, peppers, sweet corn, squash and eggplants.

For recommended varieties or cultivars, check out  Vegetable Gardening for Beginners.

Planting Guide for Common Garden Crops

Adapted from Planting a Home Vegetable Garden  by Richard Jauron, Iowa State University Extension Service.

References:

AG12-137, Vegetable Transplant Production (wvu.edu) by Dr. Lewis Jett, West Virginia University Extension Service

Vegetable Gardening For Beginners | Extension Service | West Virginia University (wvu.edu)  by Jodi Richmond, West Virginia University Extension Service

Planting a Home Vegetable Garden (iastate.edu) by Richard Jauron, Iowa State University Extension Service

SP291-A-Growing Vegetable Transplants for Home Gardens (1).pdf by David W. Sams, The University of Tennessee Agricultural Extension Service

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