For many of us, getting a head start on spring planting begins with a few plastic pots or homemade containers on the kitchen counter or top of the refrigerator where there is more warmth. If we're lucky enough, we have a special spot designed for propagation on a tiered light cart or on a heat mat in a greenhouse.


Even though we might lack ideal conditions for starting seeds, it's still possible to produce strong, healthy seedlings that will be fun to grow, save ourselves money that we'll surely spend elsewhere in the garden, and most of all, be ready to transplant when the weather is right.

One of the greatest limitations in making all of this happen is not the germination process itself but how seedlings develop when exposed to low light levels inside our homes. Once sprouts show the first sign of green as they erupt from the soil, they need bright light to begin photosynthesis, the process of making their own food that sustains their lives. But when light is too low, stems elongate and become weak and a healthy start is compromised.

Moving seedlings onto a windowsill is an obvious strategy, but even this doesn't solve the problem entirely because the sun is still too low in the sky for the next couple of months to send intense rays indoors. Besides, sunlight is often obscured on cloudy days and not all windows are south-facing where light is brightest.

What plants need most is bright natural light. An outdoor cold frame encased in glass or plastic is one solution, but it takes some monitoring to keep it from getting too hot or too cold.

If limited light is all you have to work with, it's possible to augment it by setting up a small production area using bright white, mirrored, or aluminum foil-covered reflective surfaces to direct light onto seedlings.

Indoors, the ideal setting for seedlings is under artificial light. Special grow-lights provide the same full-spectrum light that plants receive outdoors, but an ordinary fluorescent tube is perfectly adequate and comes close to replicating sunlight.

If you already have an under-the-counter fluorescent fixture, you may find it convenient to use rather than setting up something new. But because such lights usually have thin, low-wattage tubes, they support only a very small number of seedlings.

A relatively inexpensive alternative is to purchase an industrial fixture -- a shop light with 2 long tubes and a reflective hood -- suspended by small chains. It's awkward and not very pretty so you may want to rig it up in the garage, in a spare room, or closet. In other parts of the country, people generally relegate it to the basement.

It isn't the sophistication of your set-up that's important; it's the distance of the fluorescent tubes from the plants.

As soon as sprouts emerge from the soil, position them no more than 3 or 4 inches below the tubes. Keep them close for a month or until stems attain some girth. Increase the distance gradually as leaves form and plants grow tall, but never allow more than 6 to 8 inches above the growing tips.

The time factor

There are two time constraints to consider. One is the time period for exposing seedlings to light each day; the other is how many weeks they'll be under artificial light.

Twelve hours a day is a minimum exposure, but 16 hours is probably better. Any more limits the amount of darkness too severely. Plants do require dark periods since that's when, it is believed, most growth actually occurs.

To determine when to sow seed, consult seed packets for the time it takes before seedlings will be ready for transplanting. Holding them too long impacts root development.

How many weeks you keep plants indoors really depends on the weather. Cool-season crops can be transplanted outdoors whenever the soil is dry enough to be worked and during a relatively mild period -- when nighttime temperatures stay above freezing.

Warm-season crops need warm soil and warm air; so, be sure to wait until after our last frost -- usually April 15, but May 1 is safer -- and when nights stay above 50 degrees.

Hardening off

A week before you're ready to plant, begin the hardening off process to acclimate plants to tougher, stress-inducing outdoor conditions of strong sun, wind, and vacillating temperatures.

Begin by allowing soil to dry a little more between waterings. Each day, expose plants to longer, cooler periods outdoors in a sheltered spot, gradually moving them into sunlight. At the end of the week, leave them outdoors for a night or two.

A lean beginning

If you're tempted to add fertilizer to the germinating mix when you sow seeds to give them a strong start, don't. It may seem like a good idea, but too much fertility actually promotes damping off disease, a fungal infection that causes seedlings to collapse and die.

Wait to fertilize until the first true leaves appear.

Rosemary McCreary, a Sonoma County gardener, gardening teacher and author, writes the weekly Homegrown column for The Press Democrat. Write to her at P.O. Box 910, Santa Rosa, 95402; or send a fax to 664-9476.