Horticulture News: Starting your own transplants

By Kim Cowherd, Published:

Germinating and growing vegetable and flower seeds until they are ready to be planted in the garden can save you money and give great satisfaction. Home germination of flower and vegetable seed may be necessary if you plan to produce your favorite varieties of vegetables during the year or if you have an older or different variety of plant than can be found in a garden center greenhouse.

The following information from University of Kentucky Extension Horticulture gives you assistance if you decide to start your own vegetable and flower plants at home from seed.


Plan the seed-sowing date carefully so your transplants are ready to go into your garden on time. The length of time from sowing seed until plants are ready to be transplanted depends upon the cultivar and the environment available for growing.

Generally seeds of mid-season vegetable plants should be sown between March 1 and April 15 so they will be ready for the garden after the frost-free date and in our planting zone that’s the first week of May.

A variety of systems can be used for starting transplants. These systems should provide an ideal environment for both seed germination and plant growth. They should also be dependable when seeding a variety of plants and give consistent results.


Seed selection and storage. It is best to start with new seed, so order only one year’s supply. While some seed may be stored for several years with slight deterioration in quality, other seed may be viable for only one year.

Selection of germination medium. The germination medium should be well drained, relatively low in fertilizer, and sterile (free of insects and diseases). The medium can be prepared from a combination of peat, vermiculite, or similar ingredients.

However, since relatively little medium is needed for seed germination, it may be best to consider purchasing a commercially packaged growing medium from a garden supply store or greenhouse operator. Commercially packaged growing media consist of a mixture of two or more of the following materials: sphagnum moss peat, bark, perlite, vermiculite, coarse sand, processed bark or expanded shale.

These media are convenient and suitable for most plants directly from the bag. They are free from weeds, insects and diseases, and limestone and fertilizers have been added to support plants for 2-6 weeks. Most are suitable for germinating seeds as well as growing transplants.

Selection of containers. The container used for seed germination should have certain characteristics. It should be 2-3 inches deep and sterile and it should have holes in the bottom for drainage as well as for water uptake. A single container may be used for many types of plants. However, it would be best to germinate only one cultivar of a certain plant in a small container so that the environment for each may be more accurately controlled.


The germination medium should be damp before it is placed in the container. Fill the container to within about 1/2 inch of the rim. Seed should be scattered uniformly across the surface or sown in rows at the rate of 10-20 seeds per square inch.

Seeds sown too thickly will result in excessive competition among plants and spindly growth. Small seeds should be left uncovered. Cover larger seeds with a thin layer of germination medium. Most seeds will germinate in either darkness or light. Special needs regarding light and dark treatments should be stated on the seed packet.

Temperature requirements for germination. Most seeds will germinate very well when grown within a 70-80-degree F range. Again, specific temperature needs of seeds will be indicated on the seed packet. If the temperature is maintained below or above the recommended range, the germination rate will be slower and fewer seeds will germinate. Most homes are kept at temperatures somewhat below the recommended range but there may be some areas in the home that are suitable.

Moisture and humidity requirements for seed germination. Maintenance of a constant moisture level and nearly 100 percent relative humidity is important to successful seed germination. Several methods may be used.

Adequate moisture can be maintained by hand watering. However, great fluctuations in water content of the medium may occur between irrigation as it is easy to forget to water. Hand watering with cold water also reduces germination temperature.

Plastic is an excellent way to maintain high humidity and moisture levels. After seed is sown, a piece of clear plastic, placed over the top of the container, will maintain a high humidity level. The container may also be placed inside a plastic bag and sealed to prevent moisture loss.

To avoid any problems, the container should not be placed in direct sun because plastic will trap heat and damage the seeds. Secondly, the plastic needs to be removed immediately after emergence of seedlings to prevent leggy growth.

Maintenance of sterile conditions during seed germination. Fungi and/or bacteria may kill seedlings during germination. Thus the medium, container, tools and even the seed itself should be sterile. Containers and tools can be sterilized by soaking them in a 10 percent household bleach solution (1 1/2 tablespoon/cup of water) for 5 minutes.

The following suggestions should help prevent disease problems: Use seed treated with fungicide. Seed packets are usually clearly marked when seeds have been treated with fungicides. Seeds are generally brightly colored (pink, purple, green). Do not plant seeds deeper than necessary. Keep temperature constant. Provide seedlings with adequate ventilation. Avoid overwatering.


After germination, plants need a maximum of light for optimum growth. Seedlings should be transplanted to larger containers within a few weeks after germination. One application of a complete fertilizer should be given to seedlings while they are still in germination containers.

After transplanting, plants should be fertilized once a week with a complete fertilizer. The ideal temperature for growth of transplants should be 60-75 F during the time plants receives light and about 5O-65 F during darkness. Excessive night temperatures (too cool or too warm) will result in poor quality growth. The growing medium should be kept damp.

For more information log on to ca.uky.edu/agc/pubs/ho/ho56/ho56.htm. For this information in print, contact the Extension Office at 695-9035 or email Kim.Cowherd@uky.edu and request the publication, “HO-56 Starting Plants from Seed at Home.”

Another excellent publication is “Home Vegetable Gardening in Kentucky,” also available at the office, 101 Lakeview Ct.

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