How To Start Seeds

You don’t need a greenhouse to produce healthy, vigorous transplants.

April 5, 2016
Mitch Mandel

Seeds are a satisfying and thrifty alternative to purchasing flower and vegetable transplants in spring. Starting Seeds Indoors gives the gardener control over crop timing, as well as a greater selection of varieties (including many heirlooms that are not often sold as transplants). Organic gardeners take advantage of the opportunity to begin the growing process with certified-organic seeds. Success with indoor seed starting requires a suitable light source and a careful eye toward the seedlings’ temperature, moisture, and nutrient needs.

April Johnson, landscape and greenhouse coordinator at the Rodale Institute near Kutztown, Pennsylvania, grows literally thousands of organic transplants every year. Johnson uses a two-step process: First, she plants seeds in flats, and then, when the seedlings are up and growing, she transplants them to individual pots or cell packs. This technique works for many vegetable crops (broccoli, cabbage, eggplant, lettuce, onion, pepper, tomato, etc.) as well as for many annual flowers and herbs.


Related: Beginner's Guide To Seed Saving

1. Make Rows

ruler making rows in seed-starting mix
Mitch Mandel

To sow the seeds, fill a flat with moist seed-starting medium. Johnson shares this recipe for how to Blend Your Own Seed-Starting Mix. Level the medium and use a ruler or piece of lath to press shallow rows about ¼ inch deep and 2 inches apart.

2. Sprinkle Seeds

seeds being sprinkled into soil
Mitch Mandel

Sprinkle seeds into the depressions. Space seeds about ½ inch apart. If planted too closely, the seedlings will be more difficult to separate at transplant time. Label each row to identify the variety planted.


3. Scatter Excess Mix

soil scattered on top of seeds
Mitch Mandel

Some seeds germinate best in cool soil, and others in warm; check the seed packet for temperature requirements. If the seeds demand warmth, place the flat near a heat vent or on an electric heat mat to warm the soil. Watch daily for emerging seedlings, and as soon as they appear, remove the plastic cover and move the flat to a sunny window or grow lights. At this point, many types of seedlings prefer cool growing temperatures around 65 degrees.
Once all rows are planted, gently scatter more of the seed-starting medium to cover the seeds (unless the packet specifies leaving seeds uncovered). Water the surface with a gentle mist and cover the flat with a plastic dome or sheet of clear plastic to maintain moisture.

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4. Gently Loosen Plants

new plants being transplanted
Mitch Mandel


When seedlings have grown their second set of leaves, they are ready for transplanting to individual containers. Use a chopstick or letter opener to lift and loosen the soil beneath a row of seedlings. Gently tug the seedlings apart. Hold the seedlings by their leaves instead of their stems, which are more easily damaged by rough handling. Don’t worry if some roots are torn in the process, or if most of the potting mix falls away from the roots.

Related: 14 Ways To Use Chopsticks In The Garden

5. Transplant + Fill In Soil

plants in individual containers
Mitch Mandel

Add some potting mix to the bottom of a container (Here we're growing tomatoes. For the seedlings shown, we’re using 3 inch square pots). Center the seedling in the pot, then add more soil to fill.

6. Press Soil

hands pressing on soil
Mitch Mandel

Press lightly to firm the soil around the roots.

Related: What You Need To Start Seeds Indoors

7. Water Plants

watering plants
Mitch Mandel

Using a rose on the watering can, soak thoroughly.

Seedlings grown in a mix that includes dirt from the compost pile probably won’t require organic fertilizer. In compost-free mixes, feed the seedlings lightly every 2 or 3 weeks after moving them to individual pots. Johnson recommends liquid kelp and fish emulsion, mixed at half the recommended rate.

Starting about 2 weeks before you plan to transplant the seedlings into the garden, move them to a sheltered spot outdoors for a few hours at a time. This process, called hardening off, allows the seedlings to adjust gradually to outdoor conditions such as wind and sun. “Slow down on water to let them toughen up,” Johnson says. “Be careful not to put them in direct sunlight right away.” Gradually increase their time outdoors and light exposure.

Indoor seed starting requires the gardener to develop new skills, but in the end, it’s worth it. As Johnson says, “Gardening is more rewarding when you start from seeds.”