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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Obstacles to Growing Transplants Indoors

This article was published originally on 1/12/1994
Starting flower and vegetable transplants at home can be fun. Growing quality transplants requires good seed, a sterile, well-drained growing medium, proper temperature and moisture conditions, adequate light, and other factors. Since the home is usually not the best environment for growing transplants, problems occasionally develop.

Poor or erratic germination of seed may be caused by improper planting (for example, planting too deeply), uneven moisture, and cool temperatures. Medium to large seeds are sown at a depth of 2 to times their minimum diameter. Fine seed is usually dusted on the surface of the seedbed. Cool potting mix temperatures (below 70 F) delay germination. Maintain the proper germination temperature and even moisture conditions for rapid, uniform germination.

Damping-off, caused by several fungi, can cause serious plant loss. Seedlings may develop water-soaked spots on their stems near the soil surface, then collapse and die. Environmental conditions usually associated with damping-off are a poorly drained potting soil and overwatering. Damping-off can be prevented by using clean containers, a sterile, well-drained potting mix, and by following good cultural practices. Previously used containers should be washed in soapy water, then disinfected by dipping in a solution containing one part chlorine bleach and nine parts water. Flower and vegetable seed need an evenly moist potting mix for good germination. After germination, allow the potting soil to dry somewhat between waterings.

Tall, spindly growth is a common problem when growing transplants indoors. Poor (insufficient) light, excessive watering, high temperatures, excessive fertilization, and crowded growing conditions are factors which contribute to spindly growth. Once the seeds have germinated, move the seedlings to an area with somewhat cooler temperatures and good light. Place the seedlings in a sunny south window or under artificial light. It isn't necessary to have a fancy plant stand. A standard fluorescent shop fixture with one cool and one warm fluorescent tube works fine. For best results, the lights should be no more than 4 to 6 inches above the seedlings. Leave the lights on 12 to 16 hours a day. When the first pair of "true leaves" appear, thin or transplant the seedlings. Allow the potting soil to become somewhat dry between waterings. The best quality transplants are short, stocky, and dark green.

Green algal or brownish fungal growth may appear on the soil surface or sides of peat pots. While their appearance generally causes little harm, their presence usually indicates excessive moisture levels. Allow the potting mix to dry somewhat before watering.

A lack of essential nutrients produces characteristic deficiency symptoms. Phosphorus and nitrogen deficiency symptoms sometimes occur on vegetable and flower seedlings. Phosphorus-deficient plants frequently have purplish leaves and growth is stunted. Yellow lower leaves may indicate a nitrogen deficiency. Other symptoms of a N deficiency are stunted growth and small leaves. Apply a soluble fertilizer, such as 15-30-15, to the seedlings. Fertilize weekly with a one-quarter strength solution.

While there are obstacles to growing transplants indoors, home gardeners can produce good quality transplants if they follow good cultural practices.

Year of Publication: 
1994
Issue: 
IC-467(1) -- January 12, 1994