Tip of the Week — 3-9-09

Posted in Gardening Tips on March 9 2009, by Sonia Uyterhoeven

Sowing Seeds Indoors

Sonia Uyterhoeven is Gardener for Public Education at The New York Botanical Garden.

There are a number of advantages to starting your seeds indoors, among which is getting a jump on the growing season weeks before the last frost date (May 15 in New York City). Some vegetables take a long time to mature, and early sowing assures a good crop.

Starting from seed offers you a much wider selection than what you would find in already grown plants in a gardening center. Often, the more unusual and cherished varieties are only available in seed, and over the past decade, many more interesting ones, especially heirlooms, have become available.

I have many friends who like to trial heirloom tomatoes. Starting them from seed is easy and gives you more choices than you can possibly make in one season. Thumbing through the Seed Savers Exchange catalog is a great way to kindle your enthusiasm. I am personally interested in starting a basil trial and have been perusing Seeds of Change and Johnny’s Selected Seeds catalogs for inspiration.

These days, many seed companies are catering to our desire to “try a little bit of everything.” Besides the popular mesclun mix, companies now offer a variety of seed mixes such as “gourmet beet blend” and “gaggle of gourds,” which include a tasty and colorful assortment of heirlooms. Botanical Interests, Inc. is one such company that has a delightful selection of seeds.

Starting from seed is an incredibly cost efficient way to grow a large variety of herbs, flowers, and vegetables. The price of a seed packet is just a fraction of the cost of store-bought plants. Finally, it is simply rewarding to plant seeds and to watch them grow. Passionate gardeners and good cooks wait with anticipation as their summer harvest begins its seasonal cycle.

Sonia tells how to best sow seeds indoors, after the jump.

For indoor sowing, most plants should be sown from 4 to 10 weeks before the last frost date. The length of time will depend on the speed of germination, the rate of growth, and the conditions that you provide for the plant.

There are many types of seed-starting containers to choose from depending on your needs and preferences. Containers can be costly and elaborate or simple and inexpensive. Whatever you use, make sure that your container has drainage holes. If you are starting a large number of seeds, you can use seedling flats.

A good planting medium for seed starting should be porous and well drained. It should also be sterile so that it is free of pests and weed seeds. Many seed-starting mixes are available at garden supply stores. Most of these are made up of a combination of sphagnum moss, peat, vermiculite and/or perlite. Never use soil from your garden—it is not sterile, it’s too heavy, and it will hold too much water for the sensitive young seedlings.

First, moisten (not soak) the growing medium, using tepid water (slightly warm) in a spray bottle. You can also use a watering can with a rose attached. Sprinkle several times until the potting media is nice and moist.

If using a watering can, when you tip it to start watering, the sudden force of the water will create a depression or a divot where the water first hits the potting media. To avoid this, tip the can and begin watering away from the seedling flat and then run in briskly over the top of the flat for even contact.

When sowing seeds in flats do so sparingly so that there will be plenty of room for the seedlings to grow (approximately 1 inch apart). When sowing seeds in smaller containers, make sure to plant 2 or 3 seeds per container, as the germination rate never is 100 percent. Follow instructions on the label for planting depth.

Covering the tray with a plastic dome helps to keep moisture in; remove the cover once the seedlings have germinated. Label seed trays with plastic tags using waterproof markers or lead pencils.

Place the seeds on a sunny windowsill and watch them grow. If you are worried they are not getting enough heat during the germination process, stack a few books on top of your radiator and place the seedling flat on top.

Remember to keep the potting medium moist while the seeds are germinating and when the seedlings are in their early stages. The top of the medium should slightly dry out, but overall it should stay moist during the initial stages of growth.

Once the seedlings have grown, you are ready for transplanting. Harden them off by bringing them outdoors for short intervals for 1 to 2 weeks to acclimate to outdoor conditions. Finally, find a space for them in the garden.