This guide is designed for everyone, from novices to experienced seed starters.

Winter is a great time to plan your spring garden and sprout seedlings. Why should you go to the trouble of starting your own seedlings?

• One of the best reasons is cost savings. The investment you make in seeds and equipment will offset the much higher cost of purchasing seedlings from a nursery.
• Starting seeds indoors in late winter allows you to plant larger, more established plants in the spring, which yield an earlier harvest and longer growing season.
• The selection of seed varieties is so much greater than that of transplants available at plant nurseries.

A good seed starting operation requires that you:

• Start the seeds indoors where the ambient room temperature doesn’t fall below 50 degrees Fahrenheit. Supply heat to keep soil at appropriate temperature (72 to 80 degrees) for the type seed you are planting.
• Keep soil moist, but not wet.
• Supply ample light to keep plants from being leggy.

Starting from Scratch

• Space. Find a room or space such as a garage or closet to start the seeds. It should be 50 to 80 degrees Fahrenheit (warmer is better) and have room for plants and lights. Keep in mind plants need water and soil, so there is always a possibility of spills.

• Seeds. Start by planting vegetables you and your family will really enjoy until you have mastered those veggies; then start experimenting. I suggest buying seeds from reputable seed brands/suppliers, and it is great to use fresh seeds, bought this year. If you use seeds from previous years, expect that fewer of the seeds will grow than fresh seeds.
• Soil. Use good quality potting soil (not garden soil), as well as a seed starting mix or coco coir, which is a sustainable, organic growing medium made from processed coconut husks. It offers excellent water retention, aeration, and drainage.
• Lights. While it is tempting to use natural light from windows, modern windows frequently have additives to filter out ultraviolet light, heat, and light itself, which can prevent plants from getting the amount or quality of light they need. Relying on window light alone can result in weak, leggy or spindly plants that often die. For this reason, I suggest LED or fluorescent bright lights (high Lumens) that are on the cool end of the color spectrum (high Kelvin) without getting too hot. Lights should be about two inches from the top of the cell packs until the seeds sprout, then keep them 2 inches above the top leaves on the plant. Use a timer to keep lights on for 16 hours and off eight hours.

• Temperature. Use a heat pad with a thermostat to keep the soil at the appropriate temperature for the type seeds you are planting (typically 72 to 80 degrees Fahrenheit).
• Fertilizer. Depending on your preferences, you can use organic or chemical fertilizers that are granular or water soluble. I prefer water soluble for seedlings, as it is easier to apply.
• Water. Your seeds need water when the top of the soil looks dry, typically every two or three days. I suggest using one of the following methods:
  • Bottom watering: Lift one of the cell packs and pour water into the tray until it is about one inch deep then replace the cell pack. After 15 minutes drain any excess water in the tray.
  • Top watering: Carefully sprinkle water on top of the cell packs. I use a plastic water bottle with small holes drilled into the lid. Be sure to water thoroughly. After 15 minutes, drain any water that has filtered down to the 1020 tray.

Seeding

1. Read the instructions on the seed packet or look online for suggestions for when to plant outdoors in your area. While some seeds should be directly sown outdoors in their final location, many plants should be started indoors about six to eight weeks before you want to plant them in the garden. As an example, to plant tomatoes outdoors in mid-March, you would need to start the seeds January 15 – 31.

2. Fill a one-inch (or larger) 6-pack with pre-moistened potting-mix. Firm the soil down to where the cell is 80% full.
3. Place multiple seeds on the surface of the potting mix in each 1-inch cell, for example, six or so tomato or pepper seeds, 10 lettuce seeds, etc.

4. Cover seeds with pre-moistened seed starter mix or moistened coconut coir. Cover seeds to the depth stated on seed packet. If planting depth is not specified on the packet, cover to double the seed width. Don’t cover too deeply, as doing so may delay or prevent seeds from spouting. You can always add soil after the seeds have spouted.

5. Be sure to label them!
6. Put 6-packs into a 1020 daisy tray (tray with efficient drainage), and set the daisy tray into a 1020 tray (tray without drainage holes).
7. Water the potting mix in the cells carefully and thoroughly. Let them sit for 15 minutes and then drain any excess water in bottom from the 1020 tray.

8. Place trays on heat mats. Set the thermostat to the appropriate temperature for the type of seeds you are planting; typically, 72 to 80 degrees. Insert the thermostat’s temperature probe into the potting mix in one of the cells. Make sure the temperature probe is in the soil, not under the pots.
9. Keep the lights one to two inches from the top of the plants as the plants grow.

Sprouting

1. When seeds sprout, they will have two leaves (cotyledon) which are not “real” leaves. Then they will start forming “real” leaves as the plants grow, keep the lights one to two inches away from the top of the leaves.
2. Once the plants have two sets of real leaves, it is time to transplant them into larger pots (up-pot).

Transplanting (Up-potting)

1. Use larger clean pots (3.5 inches) or so. Fill to 80% full with moistened potting mix.
2. Make a hole in the soil to receive the transplant. The receiving hole should reach almost to the bottom of the pot.

3. Carefully remove plants and soil from one of the 1-inch cells. Then carefully tease the roots apart to separate into individual plants.
4. Put one plant in each of the larger pots you have prepared and firm soil around the plant.
5. Add a little coco coir or seed starting mix to the top of the soil.
6. Water gently and thoroughly from the top to moisten the soil and help ensure the roots have good soil contact. Stop watering once water is dripping from the bottom of the pot.
7. Plants no longer need to be on a heat mat if the room temperature stays above 50 degrees.
8. Keep the lights one to two inches from the top of the plants as the plants grow.

9. You can fertilize by either adding a ¼ teaspoon of dry fertilizer to the cell or by watering with liquid fertilizer diluted to about 10% of the recommended amount. In other words, if your liquid fertilizer says to use two teaspoons per gallon of water then you would want to use about ¼ teaspoon in a gallon of water.

Hardening (or Hardening Off)

As soon as outdoor daytime temperatures are above 50 degrees, start taking the trays outside to harden off the plants. Take them out in the sun for 15 minutes on the first day, 30 minutes on the second day, 45 minutes on the third day. Then you should be able to put them in an area that gets four or less hours of sun per day. Remember to take them inside at night to avoid losing them to frost.

Planting

When outdoor temperatures will support this plant species, check to see if your transplants are ready by carefully removing one from its pot to see if there are roots reaching the bottom and sides of the pot. If so, they are ready to transplant into the garden (assuming weather/frost allows).

Plant to the correct depth. For most plants, the outdoor soil should be level with the soil depth of the potted plant. However, with tomatoes, the bottom sets of leaves are often removed and then planted almost up to the leaves that remain on the plant.

About the Author

For More Information

• Texas A&M AgriLife Extension Earth-Kind Landscaping: Timely Tips on Starting Seedlings at Home
• AgriLife Extension: Texas Home Vegetable Gardening Guide
• University of Maryland Extension: Seed Starting Indoors
• Texas Master Gardeners, Collin County: Seed Starting Indoors, A Beginner’s Guide
• University of Minnesota Extension: Clean and disinfect gardening tools and containers