Larger seeds — such as those of broccoli, cabbage, cauliflower, eggplants, marigolds, peppers, tomatoes and zinnias — can be direct seeded into the containers in which they will grow until they are ready to be transplanted into the garden. This eliminates the shock associated with transplanting. Direct seeding requires more space initially, but these large seeds do not require the tender care essential in germinating small seeds.
They will germinate easily providing you keep the rooting medium moist but not wet.
The container size you select for direct seeding will depend on the rate of growth of the species and the size you want the plant at transplant time. For most vegetable transplants and most flowering plants, three- to four-inch pots will be adequate.
However, to produce tomato plants or pepper plants with fruit already well formed by the time you transplant them in the garden, you need two stages. To produce such plants, direct seed into three-inch pots. When the plants are eight to 10 inches tall, transplant them into six- to 10-inch pots. Transplant them before the roots circle the inside walls of the three-inch pots.
To start all these larger seeds, fill the three-inch pots with commercial potting medium such as Pro-Mix, Sunshine Mix, Metro Mix or Farfard Mix to the top edge of each pot. Unless the seed packet indicates that seed germination is 100 percent, which is highly unlikely, place at least two seeds in the middle of each pot and press them in the soil lightly with your fingers. If you are using seeds that you stored from previous years, sow at least three seeds in each pot. As seeds age, germination is reduced.
Irrigate each pot thoroughly until excess water drains from the bottom.
Seeds of broccoli, cabbage, cauliflower, celery, Chinese cabbage, kohlrabi, pak choi and lettuce germinate best at temperatures of 65 to 70 degrees. Sow them in March to be tall enough to transplant into the garden in early to mid-April while temperatures are cool. To prevent sunscald, acclimate the plants by placing them in trays outdoors under light shade for at least a week before transplanting them to the garden.
Seeds of tomatoes and peppers germinate best at temperatures near 80 degrees. Soon after the seeds have geminated, place them in full sun. Never allow them to dry out.
Because seeds of peppers, both hot and sweet, are slow to germinate, they should be sown in March
Like tomatoes, seeds of calendula, gazania, gaillardia, marigold, sunflowers and zinnia germinate rapidly and their seedlings develop rapidly. Delay starting these seeds until five or six weeks before you plan to transplant them into the garden.
If you wish to grow your plants organically, blend any of the potting mixes with one-third by volume compost such as crab or lobster waste compost, which will provide all the nutrients the plants need until they are ready to be transplanted into the garden. Otherwise, within six weeks of germination, you will need to initiate a liquid fertilizer program.
Ask Dr. Gouin your questions at DR.FRGouin@gmail.com. Please include your name and address.