Starting seeds indoors not only gives you earlier yields, it also extends the harvest season for tomatoes, peppers and other vegetables that thrive in warm soil and summer heat. Heavy clay or cool spring soil can put a damper on seeds sown in the ground, and the results often lead to disappointment with little harvest. Seeds simply germinate better when started in the controlled environment indoors or in a greenhouse. And this can make all the difference between harvesting only a few tomatoes or a few basketfuls.
You'll need a space to set up your nursery and a few basic supplies: growing containers, planting mix, a light source (natural or artificial), seeds and water. Choose a sunny area or location where you can hang lights, such as a bench or shelf in a greenhouse or solarium or a large sunny window in a kitchen or utility room.
All-in-one seed-starter kits that include trays, cells, capillary matting and greenhouse covers make the process simple, but you can easily put together your own kit using purchased items or materials at hand.
Any shallow container will do as long as it holds soil and has drainage holes; for example, egg cartons, halved milk cartons and toilet-paper rolls. Other options include plastic pots, peat pots and compressed-peat pellets. Flats and cells are often preferred for serious seeding. Open flats require careful handling when it is time to separate and transplant seedlings to cell packs or pots; seeding directly into cell packs is convenient and saves time. Most vegetables can be started in a 72-cell pack, although larger-seeded types -- such as squash, corn and melons -- do better in a 48-cell pack.
The basic idea is to fill containers with a potting medium to within 1/4 inch of the top, make an indentation in the soil, plant the seed and cover it with soil, and then wrap or cover the container (to keep moisture in) until the seedlings appear. A few refinements to this process will yield better results.
A light potting mix will work for starting seeds, but a seedling mix helps minimize the risk of "damping off," a fungal disease that often kills infected seedlings. (To prevent this fungal disease, use a sterile germinating mix, provide good air circulation and don't overwater.)
A better take on the "basic idea" is to fill the container to less than 1/2 inch from the top, and (skipping the part about making an indent) sow one to two seeds per cell directly on the surface. Then cover the soil to three times the seed's width with fine vermiculite. (Some seeds need light to germinate successfully and should not be covered. Be sure to read the seed packet for germinating instructions.) This procedure saves time, and the vermiculite keeps the surface moist and loose so seedlings can easily germinate and emerge.
Be sure to keep the soil moist, but not drenched, until seedlings emerge. This can be accomplished with a fine mist sprayer, placing a capillary matting underneath the container or setting the container in a tray of warm water. Covering the container does create a greenhouse effect, so you water less often, but plastic bags or wraps may encourage mold and keep the soil too saturated. If you do cover the container, opt for plastic domes. Seeds will, however, germinate uncovered as long as the surface stays evenly moist.
Seeds started in cool locations may need a propagation heat mat or heating cables to aid germination. Any covers or heating elements should be removed after the first few sprouts appear.
Keep in mind that growing seedlings need light. If the available natural light is insufficient, place the container under fluorescent lights (about 12 to 16 hours a day) so seedlings always remain 1 to 3 inches below the lights. Continue watering as needed so the soil stays slightly moist. Feed with a diluted liquid organic fertilizer, such as fish emulsion or compost tea.
Watching seedlings emerge is a magical process that the entire family can take part in and enjoy. There's no better time to start than now. As Henry David Thoreau once wrote, "Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders."
TIMING IT RIGHT
Broccoli, cabbage, cauliflower, lettuce and other greens can go out when they are 4 to 6 weeks old. (Be sure to harden off the seedlings before you transplant them outdoors.)
Melons, cucumbers, tomatoes, squash and peppers can go out at 6 weeks without potting up as long as they were sown in a 48-cell pack or 2-inch pots. You can get a jump on the season by sowing this group up to 10 weeks before your last spring frost and then potting them up into larger containers so they can grow bigger before planting outside. (Use a potting mix enriched with compost or organic fertilizer when potting up seedlings.)
Almost any vegetable becomes less of a challenge when it is started inside rather than being sown directly in the cool, spring soil. But once in the ground, some varieties are more demanding than others. Easy-to-grow varieties let you succeed regardless. Tasty contenders include 'Arcadia' broccoli; 'Golden Acre' cabbage; 'Snow Crown' cauliflower; 'Cool Breeze' and 'Marketmore 97' cucumbers; loose-leaf 'Red Sails' and heirloom 'Speckles' lettuce; 'Northstar' and 'Gypsy' sweet peppers; 'Eight Ball' summer squash; and tomatoes 'Celebrity,' 'Early Cascade,' 'Green Zebra,' 'Stupice' and 'Sun Gold.'
GREENHOUSE AND COLD-FRAME TIPS
Greenhouses are generally classified as being either cool or warm and vary from portable to permanent. The tips that bring success will vary depending on your greenhouse.
In an unheated greenhouse, heat mats and cables are essential for starting seeds in the late winter and early spring. The key is to create a warm environment for germinating seeds, a cooler (50 to 70 degrees Fahrenheit) environment for growing seedlings, good air circulation and adequate drainage. Slatted tables and benches not only are ideal for elevating flats and growing plants off the ground, they also improve water drainage and air flow. When the greenhouse is closed up tight, one or more fans will help circulate the air.
Greenhouses and cold frames can quickly heat up on a clear day, especially once spring weather and a clear day arrive. Of course you'll want to open the windows and vents, but shade cloth can also help keep things cool. Cold frames are great for hardening off plants before putting them in the ground. But a heated cold frame, known as a "hotbed," can also be used to start seeds and grow seedlings. Both electric heating cables and soil heating cables that you bury in the soil work well. Many come equipped with a built-in thermostat that automatically turns on the cable when soil temperatures are low.
Nichols Garden Nursery
Territorial Seed Co.
West Coast Seeds
More tips on starting seeds are online at Homes & Gardens on OregonLive.com
Garden writer Kris Wetherbee is the author of "Attracting Birds, Butterflies & Other Winged Wonders to Your Backyard"