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Sowing Seeds: Sowing Seeds Indoors

Photo Courtesy of Flickr cc/Pink Sherbet Photography
Photo Courtesy of Flickr cc/Pink Sherbet Photography

There are a number of advantages to starting your seeds indoors:

  • You can get a jump on the growing season by starting seeds several weeks before the last frost date (see 'When to Start Your Seeds' below). Some vegetables take a long time to mature and early sowing assures a good crop.
  • Starting from seed offers you a wider selection of plants than can be found in most garden centers. More unusual and cherished varieties are often only available as seed. Over the last decade, many interesting and unusual seed varieties have become available, especially heirlooms.
  • Many seed companies are catering to our desire to try a little bit of everything: besides the popular mesclun salad mix, companies now offer a variety of seed mixes such as 'gourmet beet blend' and 'gaggle of gourds' that include a tasty and colorful assortment of new and heirloom varieties.
  •  Starting from seed is a cost-efficient way to grow a large variety of herbs, flowers and vegetables. The price of a seed packet is just a fraction of store-brought plants.

Finally it is simply rewarding to plant seeds and watch them grow. Passionate gardeners and good cooks wait with eager anticipation as their summer harvest begins its seasonal cycle.

When to Start Your Seeds

When sowing seeds either indoors or out, it is important to know the average date of the last spring frost for your area. In New York City, this date is approximately May 15th. Perennials should be planted ten to twelve weeks before this date; most annuals can be planted four to six weeks before the last frost, and the dates for vegetables range from four to ten weeks, depending on what you are planting.


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.  You can use milk cartons, egg cartons and Styrofoam cups. Whatever you use, make sure that your container has drainage holes. If you are starting a large number of seeds, you can use plastic trays or flats. Popular seed-starting containers are made of peat fiber or processed cow manure (Cowpots). These can be planted directly in the ground, allowing your seedlings to be transplanted without disturbing their roots.

Planting Medium

A good planting medium for seed starting should be porous and well-draining. It should also be free of pests and weed seeds. Many seed-starting mixes are available at garden supply stores. Most are made of sphagnum peat, vermiculite, and/or perlite. Look for mixes that are designated for seed starting; some of the other mixes on the market are too heavy for the purpose.

Sowing Seeds

First, moisten (not soak) the growing medium, either using warm water in a spray bottle or dampening it in a bucket. The mix should be damp but not soggy. When sowing seed in flats do so sparingly so that there will be plenty of room for the seedlings to grow. When sowing seed in smaller containers, make sure to plant 2 to 3 seeds per container as germination rate is never 100%.

Follow instructions on the labels for planting depth. Most seeds need to be planted at a depth of 2 to 3 times the diameter of the seed. When planting large seeds, create a small furrow by pressing a ruler ¼ inch into the mix. Cover seeds lightly with either vermiculite or the potting medium. Some seeds, however, need light to germinate. Simply place those on top of the medium and gently press them in. After planting, mist the surface of the mix.

Covering the tray with a plastic dome or a clear plastic bag helps to keep moisture in; remove the cover once the seedlings have germinated. Seeds will not germinate if they are too dry, too wet or too cold. Initially, they prefer a temperature of 70 degrees F while germinating.  Placing them on top of the refrigerator in your home is a good place to start the germination process.

Check your seeds every day. If the top of the mix feels dry, water gently. Either water from below by filling a tray with an inch of water and laying the flat in it to soak up the water, or water from above by attaching a rose to your watering can to break the pressure of the water. The best way to water in a uniform manner is to start pouring away from the seed flats and then make a sweeping motion over the flats or containers.

Brassica seedlings being hardened off to acclimate to outdoor conditions; photo courtesy of Flickr cc/ Spraints
Brassica seedlings being hardened off to acclimate to outdoor conditions; photo courtesy of Flickr cc/ Spraints

Care of Seedlings

Seedlings grow best in full sun. A south-facing window in your home is ideal. As the seedlings grow, keep the soil moist but not wet.  The temperature should stay in the range of 60 to 70 degrees F. When the first two true leaves appear, thin the seedlings by removing all but the strongest from your trays. When seedlings have two sets of true leaves they are ready for the garden. When transplanting, be careful to disturb the roots as little as possible; transplanting is enough of a shock. When handling seedlings, always hold them by the leaves and not the stems. If you damage the stem the plant will probably not recover.

Hardening Off Plants

The term hardening off refers to a one to two-week period of exposure and acclimation to outdoor weather conditions before planting in the outdoor garden. On warm days, place the plants outdoors in a protected area, and bring them in at night. Protecting your plants from wind and intense direct sunlight is important. 

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