Sowing Seed for Fall Transplants

by Bill Adams, County Extension Horticulturist, ret'd
Texas AgriLife Extension Service

Arugula (Eruca sativa)

If you haven’t already done so, this is the time to begin sowing seeds for fall transplants. By starting seeds now, you can have pansies, calendulas, Johnnie-jump-ups, flowering cabbage, and flowering kale, as well as broccoli, cauliflower, cabbage, Chinese cabbage, lettuce, and other cool-season transplants ready to plant in the garden in September or early October.

If starting your own transplants has been disastrous for you in the past, especially in the spring, then take heart because starting fall transplants is easier. Since the soil is not as cool as it is in spring, there is not much damping-off disease. Gardeners are able to start the transplants outside where they can get plenty of sunlight. However, it is best if the transplants don’t get too much sun - morning sun and afternoon shade make a good combination.

Although many containers can be used to grow seeds in, the most convenient I’ve found is the foam coffee cup. Simply poke three to four holes in the side at the bottom of the cup. Write the name of the variety being planted on the side of the cup; it will remain there without getting lost, as so often happens if you use labels. An additional advantage of the coffee cups is that they’re white and reflect heat.

The next major concern is a potting soil mix. Many standard potting soils will work fairly well, but you can make your own. To one bushel each of vermiculite and peat moss (finely ground pine bark can be substituted for peat moss), add 10 tablespoons of 0-20-0 (superphosphate) and l/2 cup of a garden fertilizer such as 12-24-12. Mix the material thoroughly, scooping into the bottom and throwing each shovelful on the top, pyramid fashion, or roll the mixture back and forth in an old tarp. The soil should be watered down slightly so it’s damp but not soggy.

Most seeds should be barely covered with the soil mix, but some tiny seeds like lettuce need not be covered at all. Water them in thoroughly by setting them in a pan of water and allowing the cup to soak from the bottom. After they rain, put them in a plastic bag out of the sunlight. Within a few days, the seedlings will begin to make growth. As soon as this happens, you’ll need to get the containers out of the bags an into a well ventilated area. As the seedlings begin to grow, use any soluble houseplant fertilizer to keep them growing vigorously.

If you’ve had problems with disease in the past, you might want to use a fungicide twice, once at planting and again at germination. Captan is good. Lightly dust the seeds prior to planting. Captan or benomyl can also be used to drench the young seedlings just as they come up. Before you know it, you’ll have a pot full of tiny seedlings that can either be transplanted into individual containers or, if there aren’t too many in a pot, you can hold them until time to go into the garden. Perhaps the simplest technique is to plant two or three seeds in each pot, then thin them to one plant after a few weeks.

If you go the transplanting route, be sure that you handle the young seedling only by the leaves. If you grasp the stem and damage it to any extent, the young seedling will be stunted. Pots for transplants should be filled to within 1/4 inch of the rim. A pencil can be used to make a hole in the center of the potting soil mixture. This is where a little moisture is critical, since a dry soil won’t allow the hole to stay open. Carefully lower the seedling roots into the hole, and then use the pencil again to firm the soil against the root system. Be sure to water the plants carefully, uprighting any that get buried in the soil. Before you know it, you’ll be eating your own delicious homegrown broccoli.

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