Starting Seeds, Part 3

Growing Seeds

By Ron Dieter, Sunnyfield Greenhouse & Gardens

February 23, 2000

Last time we discussed sowing garden seeds into flats or packs to grow them on to transplanting size. In order to get them growing sturdy and strong, it is important to have good control of light, moisture, and heat.

Providing good lighting for seedlings is fairly easy. For less than ten bucks, you can buy a two-bulb four foot florescent light fixture that will do the trick. Don't waste your money on "grow-lite" bulbs. A plain cool white florescent tube will do quite nicely for less than a fourth of the cost. Your little seedlings will look pretty under those fancy "grow-lite" tubes, but they won't grow any better.

The fixture needs to be about eight inches above the flat. At that height, the light will be strong enough that the seedlings won't stretch and grow flimsy. The fixture will contribute some heat to the growing area also. You can easily put two flats end-to-end under the fixture and still provide adequate light. The lights should be turned on at least sixteen hours a day.

How about just placing the flats in a sunny window? That's not a good idea. The light will not be strong enough (even though it looks bright enough) and even sunny windows are cold and drafty on winter days. You have much more control of the environment using artificial light and keeping the seedlings away from drafty windows and doors.

Now let's consider moisture. The growing medium should always be moist (but not saturated) so that the seedlings never dry out. Using a plastic cover over the flat helps conserve moisture. Some seed starting kits include a rigid plastic cover that snaps onto the flat. They work well and they're handy. You can easily open them up to check the crop and add moisture. A plastic bag from the dry cleaners works, too, if you keep it propped up over the seedlings.

A spray bottle (like what window cleaner comes in) is a good way to add moisture without blasting the seedlings out of the flat. Use good quality water warmed to room temperature. Never use softened water or water high in salt concentration, especially on impatiens or salvia.

Temperature is the most difficult growing factor to control. This is where most home gardeners have problems. If the temperature is too high the seedlings grow too rapidly and begin to stretch and fall over. When there is too little heat, they don't grow at all and often die.

A soil thermometer is a good investment for seed growers. Keep the soil temperature between 70 and 80 degrees for germination. If your light fixture doesn't provide enough heat, try to find a warm spot in the house. Some folks find the top of the refrigerator or near the furnace is a nice warm spot. If all else fails, there are heating mats available to provide good growing temperatures. Never use an electric blanket for obvious reasons.

Now the trick to this whole growing process is to produce seedlings at just the right size for planting outside when the weather is right. The most common error made in this regard is having seedlings ready too soon. Once a young plant is up and growing strong, it needs cooler temperatures and bright light. Otherwise it starts to stretch and become weak and useless. Most homes are too dark and too warm for adolescent plants. Commercial growers move these young plants from the germination building to the greenhouse where the light is bright and the air is cool. Most homeowners don't have that luxury and so timing is much more crucial for them.

For some crops, such as pansies and snapdragons, a cold frame with some night heat works well. For cold sensitive plants like tomatoes and peppers, it is better to have them behind schedule rather than ahead.

If this is your first time starting seeds, I suggest you wait until April first and then plant tomatoes, peppers, marigolds, and zinnias. You'll get the knack of growing and the plants will be ready to set out by mid-May.