Smith County Horticulturist
Commercial transplant growers can’t offer all of the hundreds of varieties offered by seed companies. Also, by paying attention to timing, you can be sure you’ll have transplants when you are ready to plant.
To give your plants the best start in life, pay particular attention to the soil. Commercial vegetable and flower bedding plants are grown in what is called a soilless mix, because it contains no soil from the yard.
Rather, these are mixes of peat moss, compost and other components that contain no disease organisms that can cause premature seedling death (called damping off).
These mixes also provide excellent porosity for the new roots of seedling plants. Very good premixed, soilless potting soils designed for starting seedlings and growing transplants can be purchased in nurseries and garden centers.
Many types of containers can be used to grow seeds, from commercial to things scrounged from around the house. Foam or waxed coffee cups are convenient containers for growing individual seedlings. Simply poke three or four holes in the side at the bottom of the cup. Write the name of the variety on the side of the cup where it will remain without getting lost, as so often happens if you use labels.
If you use recycled plastic nursery pots, first soak them in a 10 percent bleach solution to kill soil-borne disease organisms that might be hanging out from previous uses.
Start seeds early to allow time for germination and seedlings to develop enough to survive the transplant to the great outdoors. Peppers require seven to eight weeks, and tomatoes five or six weeks to grow to transplanting size. Squash, cucumbers and other cucurbits require only two to three weeks to grow to an ideal size (and do not like to remain in small containers, so don’t start them too early). Members of the cabbage and lettuce families need four to five weeks.
Flowering annuals and perennials vary greatly in the time required to produce a size suitable for transplanting. Keep a garden notebook and record seeding dates, length of time to germinate and time required to reach transplant size.
Presoak tomato and pepper seeds in warm water for several hours to give them a head start. Don’t bury the seed too deep. The seed packet should give the correct planting depth. After seeding, water the soil gently but thoroughly. Place containers in plastic bags or cover the soil surface with plastic film to maintain humidity. Remove plastic at the first sign of seedling emergence. At that time, place seedlings in a sunny window, or very close to artificial lights.
Low light levels will result in weak and spindly plants. If your seedlings were started in community trays, move them to individual pots when the first true leaves are forming, usually two to three weeks after sowing.
Set the seedling at the same level it was in the seedling flat. Handle the young seedling only by the leaves. If you grasp the stem and damage it, the young seedling will be stunted. Use a pencil to make a hole in the center of moist potting soil mix.
Immediately after transplanting to individual pots, gently water your plants. Water only when moisture can no longer be squeezed out by pinching the medium between the thumb and forefinger. Apply enough water so that some drips out of the drain holes in the bottom of the container. Be sure the water is passing through the root zone, not just down the inside wall of the container.
After seedling emergence and during early development, promote strong growth by watering with a water-soluble fertilizer. Follow label instructions, and use this solution when watering.
Stockier transplants can be produced if they undergo just a little stress. A fan blowing a very gentle breeze across the plants can produce this effect. Another method is to gently brush the tops of the leaves a few times a day. In one research test, tomato plant seedling height was reduced by 20 percent, resulting in stockier transplants
Soon your transplants will be ready for setting out into the garden. Condition them to the outdoor environment for several days before transplanting. Do not quickly place containers in full sun, but find a protected area where they will get bright light and plenty of air circulation.
Monitor soil moisture every day. Gradually expose them to more direct sun. After transplanting them into the garden, be ready to protect them from adverse weather the first few days.
Keith Hansen is Smith County Horticulturist with the Texas A&M AgriLife Extension Service. His web page is http://EastTexasGardening.tamu.edu His Blog is http://agri-life.org/etg.