By Cheryl Huckabee, Denton County Master Gardener Association
Have the enticing pictures of landscape plants, flowers and vegetables shown in gardening catalogs tempted you to try growing plants from seed, but you were not sure how? Here are some guidelines to get you started toward successful seed starting.
Get Ready
- Purchase or prepare a disease-free (pasteurized) soil-less germinating mix. Instructions for making your own seed-starting mix can be found online at this link from Texas A&M Earth-Kind® Landscaping (https://aggie-horticulture.tamu.edu/earthkind/landscape/starting-seedlings-at-home/)
- Choose containers that are at least 3-inches deep, cleaned and sanitized with a weak solution of bleach and water. Peat pots, milk cartons, and egg cartons work well too. Just be sure to punch holes in the bottom of the containers to allow water to drain.
- Purchase a heat mat to warm the soil under your containers and use plastic bags or plastic wrap to cover the containers and maintain moisture until the seedlings sprout.
- Identify a location that provides 6 to 8 hours of light daily such as a south-facing window or purchase a grow light.
- Have a transplanting mix on hand if you plan to move seedlings into larger containers.
- Create labels for the containers.
- Choose seed types that grow well in North Texas and read the seed package for any guidance on desired starting location. Keep in mind that our spring growing season is shortened by hot weather in June. Choose varieties that have a short time-to-maturity period for spring gardens. The fall season is a smidgeon longer.
Sowing Your Seeds
- Plan to sow your seeds 6 to 8 weeks before the last frost in spring which is typically mid-March in North Central Texas. For a fall harvest, sow them eight to twelve weeks before the first freeze date, generally late November in our area.
- Check the seed packet for seed preparation recommendations. Some seeds germinate best if soaked in warm water overnight, other seeds with hard coats may need to be scarred – nicked or scratched – to promote germination.
- Prepare the germinating mix by wetting it thoroughly and letting it drain. It should be moist enough to hold together when you squeeze it in your hand, but should not be soggy or dripping water when squeezed.
- Fill the containers to about 1” from the top with the germinating mix.
- Make shallow indentations of about ¼” in rows if in a flat or a ¼” hole if in a pot.
- Lightly sow the seeds of a single plant type in each container, check the seed packet label for the recommended seed spacing. If you’re sowing in pots put 2 to 3 seeds per hole.
- Very lightly tamp down the seeds to ensure contact with the soil. Cover the seeds with just enough soil so that you can no longer see them, usually ¼” to ½”. The seed packet will usually include the recommended seed planting depth.
- Mist/spritz the surface of the soil to dampen it.
- Cover the container with plastic wrap or set inside a plastic bag that can be closed with a twist tie or zipper lock.
- Place the container on a heated germination mat if you’re using one.
Caring for Your Seeds
- Be patient! Many seeds will germinate in 4 to 5 days but some will take as long as 2 to 3 weeks.
- Check the soil moisture daily. If the inside of the plastic cover has condensation, then no water is needed. If the top of the soil feels moist, no water is needed. If the top of the soil feels dry, lightly mist or spray the surface of the soil to dampen it. Too much water can cause the seeds to rot.
- Remove the cover once the seeds have germinated by showing the first set of true leaves. Remove the heat mat.
- Apply a small amount of balanced water-soluble fertilizer to your soil after seedlings sprout to accelerate their growth and strength.
Readying Your Transplants
- Newly germinated seedlings need full exposure to light. Place them in a bright location such as a sunny window or under grow lights.
- Water from the bottom, watering the soil only, with a half-strength balanced water-soluble fertilizer. Water only when the soil feels dry when rubbed between your fingers. One of the most common causes of seedling failure is damping-off fungal disease caused by excessive soil moisture or poor ventilation. Do not allow the container to stand in water.
- After the seedlings have grown 2 to 3 sets of leaves, thin out the weakest seedlings by cutting them off at soil level. This is an important step because plants need adequate growing space to be healthy and strong. The seed packet will often have thinning recommendations.
- Harden off your seedlings one week to 10 days before transplanting into the garden or landscape. This allows them to get acclimated to the outdoor environment. Hardening off is done in stages beginning with one hour per day of exposure to sun and normal environmental conditions. Increase the exposure by an hour each day until the plants are on their own for 8 hours.
- When you are ready to transplant into the garden or landscape, carefully remove the seedlings from the container by pushing from the bottom or sliding a pencil or spoon down the side of the container to lift the seedling out from under the roots. Do not be tempted to pull them out by the stem.
- Set the seedling in the soil at the same level it was in the container and water thoroughly. New transplants may need to be watered every 2 or 3 days to get established. Water thoroughly if the soil is dry 1-inch deep or the plant shows signs of wilting. Once established, most plants require only 1-inch of water on a weekly basis.
Growing your own plants from seeds is a terrifically fulfilling endeavor! Enjoy nurturing your babies into healthy, beautiful plants, and imagine taking home a blue ribbon and a cash prize from the Denton County Fruit, Vegetable, Herb & Flower Show on June 20! See DCMGA.org for details.
Sources & Resources
Starting vegetable plants from seeds: https://dcmga.com/files/2019/11/starting-from-seeds-HV.pdf
“Seed Propagation: Care of Seedlings.” dcmga.com, Denton County Master Gardener Association, 1 Sep. 2016, txmg.org/denton/files/2016/09/seed_propagation_allpages.pdf.
Jaane, E.E. & Roberts, Dr. R.E., “Timely Tips on Starting Seedlings at Home.” aggie-horticulture.tamu.edu, Texas A&M AgriLife Extension Earth-Kind® Landscaping, Jan. 2001, aggie-horticulture.tamu.edu/earthkind/landscape/starting-seedlings-at-home/.
Welch, PhD., William C. “Back to Basics: How to Start Seeds Indoors.” aggie-horticulture.tamu.edu, Texas A&M Cooperative Extension, 1 May 2002, aggie-horticulture.tamu.edu/newsletters/hortupdate/hortupdate_archives/2002/may02/art2may.html.
Atchley, Betty. “Starting Seeds in Pots.” easttexasgardening.tamu.edu, Texas A&M AgriLife Extension Service – Smith County, 27 Jul. 2014, easttexasgardening.tamu.edu/2014/07/27/starting-seeds/.
