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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.

Problems Encountered by Home Gardeners When Growing Transplants Indoors

This article was published originally on 3/8/2013

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 not the best environment for growing transplants, problems occasionally develop. 
 
Poor or Erratic Germination
 
Poor or erratic germination of seeds may be caused by improper planting (for example, planting too deeply), uneven moisture, and cool temperatures. 
 
Fine seeds and those seeds which require light for germination should be sown on the surface of the germination medium and then lightly pressed into the medium. Cover medium-sized and large seeds with additional potting mix to a depth of 1 to 2 times the seed's diameter. 
 
Uniform moisture levels are required for optimum seed germination. To maintain uniform moisture levels, place clear plastic food wrap over the containers. Flats can also be covered with clear plastic domes. Remove the plastic food wrap or dome as soon as germination occurs. 
 
Most seeds germinate best when the medium temperature is 70 to 75 degrees Fahrenheit. Placing containers in a warm location in the house, such as on top of a radiator or near a heat register, usually provides suitable germination temperatures. In cool environments, electric heating cables or mats can be used to insure warm medium temperatures. 
 
Tall, Spindly Growth
 
Tall, spindly growth is a common problem when growing transplants indoors. Poor (insufficient) light, excessive watering, high temperatures, excessive fertilization, and crowded conditions are factors that contribute to spindly growth. 
 
Proper growing conditions should produce short, stocky transplants. Immediately after germination, move the seedlings to an area with a temperature of 60 to 70 degrees Fahrenheit and place them under fluorescent lights (a sunny window usually doesn't provide sufficient light). A standard fluorescent shop fixture containing two 40-watt tubes (one cool white and one warm white) works fine. Position the fluorescent lights no more than 4 to 6 inches above the seedlings. Leave the lights on for 12 to 14 hours a day. Thoroughly water the seedlings when the soil surface becomes dry to the touch. Fertilize every two weeks with a dilute fertilizer solution. Seedlings growing in flats should be transplanted into individual pots or cell packs when the first "true" leaves appear. 
 
Collapse and Death of Seedlings
 
The collapse and death of seedlings is usually due to damping-off. Damping-off is caused by several different fungi. Environmental conditions associated with damping-off are poorly drained potting soil, overcrowding, and excessive watering. Damping-off can be prevented by using clean containers, a sterile, well-drained potting mix, and by following good cultural practices. Wash previously used containers in soapy water, then disinfect by dipping them in a solution containing one part chlorine bleach and nine parts water. Sow seeds thinly to avoid overcrowding. Flower and vegetable seeds need an evenly moist potting mix for good germination. After germination, allow the potting soil to dry somewhat between waterings. 
 
Yellow-Green Seedlings
 
A nutrient deficiency is likely responsible for the sickly yellow-green color. Nitrogen and phosphorus deficiencies sometimes occur when flower and vegetable seedlings are started indoors. Symptoms of a nitrogen deficiency include yellow-green foliage and stunted plant growth. Phosphorus-deficient plants have purplish leaves. Applying a dilute fertilizer solution once every two weeks should help supply adequate nutrients to the seedlings. 
 
While there are obstacles to growing transplants indoors, home gardeners can produce good quality transplants if they follow good cultural practices.