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Propagating Perennials from Seeds

Martha Stewart Living Television

A garden overflowing with beautiful, hardy perennials is not as mysterious or impossible as you might initially think. Some perennial varieties, like Digitalis purpurea 'Foxy,' Echinacea purpurea, and Platycodon grandiflorus, can be easily raised from seed and may even flower in the first year.

Easy, fast-growing perennials like hollyhocks and Rudebeckia hirta can be planted in the garden ten to sixteen weeks after seed sowing. To determine sowing date, count back from when you hope to move the seedlings outside. For germinating seeds, use porous, fiber flats measuring ten by six inches or twelve by ten inches. Both are three inches deep, which allows roots to develop more fully and retain moisture.

Use a sterilized seedling medium of peat moss, vermiculite and perlite. Its fine texture allows fast drainage and air circulation. A misting bottle will help moisten the medium in a plastic dishpan. The medium should be just damp enough to hold together when balled in your hand, yet crumble easily when you press down on it with your thumb. Fill the flats with the moistened medium and lightly tamp it down to make a flat surface for sowing the seeds across. This helps with even watering and drainage. For tamping, use a quarter-inch piece of plywood cut to fit the flat, to which attaches a cabinet handle.

When sowing small seeds such as poppies, use a salt shaker with a spring-loaded lid to ensure that the seeds don't all end up in one corner of the flat. Another method to help with spacing seeds is to mix a few pinches of coarse sand with your seed in a small cup and sprinkle by hand across the surface of the flat. The seeds should then be firmed into the soil surface with the same tamper used to firm the soil into the flat. Larger seeds like hollyhocks should be sown by shaking a light covering of seedling mix through a colander.

Mist the sown seeds well, then place the flat in a basin of water deep enough to reach halfway up its sides. Allow the flat to sit and soak up the water for ten to fifteen minutes. Remove the flat from the basin, let the excess water drain off, and label with the plant name and the date sown. This label helps you to track the days it takes a seed to germinate and will be useful for recording information in a gardening journal.

For best germination, the flats should be kept at sixty-five to seventy degrees. A propagation mat with a wire tray will elevate the flats over a heat source while allowing warm air to circulate and hasten the germination process. If you want to place flats on a radiator to act as a heat source, Robert suggests inverting a cookie sheet and setting the flats on the sheet. This helps reduce rate of evaporation.

Some seeds, like columbine, need a period of cold to promote better germination. First, make a 50-50 mix of vermiculite and perlite and moisten lightly. Add your seeds to the mix and combine gently. Put this mix into a re-sealable plastic bag and store in a dark, warm cabinet for a week. Next, place the bag in the refrigerator for six to eight weeks. After that time, sow the seeds into a flat using the techniques described above.

Thin densely sown seedlings with tweezers, removing the smallest and leaving the faster growing, stronger young plants. Transplanting can take place when the first set of ''true'' leaves has developed. Gently loosen the soil around the base of the seedling using the pointed end of a wooden plant label. Each seedling can be moved to its own two-inch-square container, filled with a soil-less seedling mix that you can find in most good garden centers and catalogs. Use the plant label's point to make a hole in the seedling mix roughly the same depth of the seed flat. Place the seedling, roots first, into the hole, coaxing it carefully into place. Firm the mix around the seedling, taking care not to damage the young roots. Water the seedling thoroughly. Check daily to maintain even moisture levels and wait a week before beginning a fertilization program.

Feed your seedlings with a very weak liquid-fertilizer solution -- about a tablespoon per gallon of water. A low-nitrogen, high-phosphorus ratio will promote healthy roots and help the young plants on their way. Place your new transplants in bright light, but not direct sunlight. The temperature range for perennials can be much cooler now than during the germination process. In fact, warm daytime temperatures and cool evening temperatures will mimic the conditions outdoors and will promote healthier growth. You'll find specific information on the seed packets.

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