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Growing Seeds Under Lights


Use fluorescent light bulbs that mimic the full spectrum of sunlight to grow the healthiest seedlings. Alternatively, use a combination of red and blue tinted fluorescent light bulbs. Do not use all red or all blue tinted fluorescent light bulbs or the growth of your seedlings will be stunted or leggy.


Resist the urge to mist and frequently water your seedlings; water only when the surface of soil begins to feel dry to the touch. Seedlings that are subjected to high humidity or frequent watering are more likely to come down with a syndrome known as “damping off.” This is characterized by the seedlings rotting at soil level, turning limp and falling over.

If you’re on a budget and want to plant many different plants in your garden without spending a lot of money, grow seeds under lights indoors and plant them in your garden after the weather warms. Starting your own seeds has another benefit besides saving money: You have the choice of many more varieties to grow than you do if you purchase plants someone else has started. One four-foot fluorescent light fixture with two bulbs emits enough light to start two or three dozen small pots of seeds indoors.

Set up a seed starting stand. You should be able to move the lights up and down as the plants grow so they are never more than 3 to 4 inches above the tops of the seedlings.

Use individual 2-inch pots, individual peat pots, or large shallow flats to grow seeds under lights. Fill up the containers to the top with the growing medium.

Sprinkle seeds on the surface of the growing medium and cover with a thin layer of the growing medium.

Water newly planted seeds from the bottom. Place the individual pots into a large, shallow container. Carefully add water to the container until it comes about half way up the sides of the pots. Let the individual pots of seeds sit in the water until the surface of the growing medium looks damp. Remove the pots and allow them to drain. Continue watering the pots of seeds and seedlings in this manner until the plants are 3 to 4 inches high.

Put the pots under the lights as soon as the seeds begin to germinate. Position the lights so they are only 3 to 4 inches above the tops of the seedlings. Raise the level of the lights as the seedlings grow. Leave the lights on 14 to 16 hours each day.

Thin the seedlings when they stand about 2 to 3 inches high. Use small scissors to snip off the unwanted seedlings at soil level. Leave the strongest and healthiest plant in each pot. For seedlings planted en masse in large flats, thin so they stand 2 to 3 inches apart in all directions.

Fertilize seedlings after thinning them. Feed weekly with a water-soluble fertilizer mixed at half the manufacturer’s recommended rate of application. Water the seedlings with the mixture when their soil is damp; never apply fertilizer solution when the soil is dry.

Begin to harden off seedlings outdoors when the seedlings are 4 to 6 weeks old and after spring weather warms to comfortable daytime temperatures. Put the seedlings in the shade for a longer period of time each day until they’re outdoors all day long. After this, move the plants into full sun for a longer period each day until they are in full sun all day long. Bring indoors at night if temperatures are expected to dip to freezing or below.

Plant hardened-off seedlings in the garden.

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