Expert’s Tip: Seed Starting

Patti Nagai, Horticulture Educator, Racine Co. UW-Extension

Master Gardener Volunteers and GreenWorks participants place seeds in flats.

Master Gardener Volunteers and GreenWorks participants place seeds in flats.

It is not too early to plant! We sowed pansy, geranium, aster, canna, and other flower seeds in our Green Works greenhouse in the past 3 weeks. Herbs and cool season vegetables are next, and it won’t be long before we start seeding warm season vegetables.

Jack plants seeds at home using recycled milk jugs.

Jack plants seeds using recycled milk jugs.

Cool season vegetables like cabbage, kohlrabi, spinach, and mustard can be started indoors if you have a cool space in which to grow them. An outdoor cold frame is useful for many cool season plants. Once the seedlings are growing they can be moved into the protected cold frame on days when the temperatures are above freezing. The cold frame is covered with a clear glass or plastic lid that lets light in, and the temperature at seedling level is ideally in the 40 to 55 degree range, perfect for those cool season crops.


Whether flowers, vegetables, or herbs, consider these factors before investing in planting seeds:

  1. Read the seed packet and the description of the seeding requirements! The information you need for a successful planting should be on the back of the package. It will tell you how long germination takes, how long till ready to transplant, and what, if any special conditions are needed. Read carefully; some seeds require light to germinate and should not be covered with soil. Others require darkness, and may germinate better covered with foil instead of clear plastic during that early germination stage (remove, of course, as soon as any signs of seedlings appear!)
  2. Use clean containers and clean soilless germination mix. Germination mix (on right in photo at right) is finer than regular soil mix (on left in photo at right), and gives better seed to soil contact. It is also light and well-drained which helps keep roots healthy.
  3. Drainage is important, the germination mix should be moist, but not soppy wet! Drying out during germination is deadly, keep the mix moist continuously. A layer of clear plastic over the top of the container can help keep the moisture in, or you can mist the top of the soil several times a day. Some seeds will germinate in 3 days, others may take 3 weeks.
  4. Many seeds germinate well with bottom heat, but once germinated most appreciate and grow better with fluctuating day and night temperatures, so turn off those heaters. Cool season flowers and vegetable will develop better if you can keep the seedlings from getting too warm. Try to keep them in that 50 to 60 degree range during the day, cooler at night.Patti Nagai, Racine County UW-Extension Horticulture Educator (retired)
  5. Bright light from a window is great, but seedlings need really bright light to develop healthy, thick stems and proper growth. Consider installing a bank of fluorescent lights on a pulley so the lights can be lowered to just a few inches above the developing seedlings. If you are into new technology, check out the new LED light systems designed for growing plants.
  6. Set up a fan to blow on your seedlings. This helps protect the delicate seedlings from damping off, a fungal disease that attacks the new stems at the soil level. The movement also triggers an amazing series of molecular events in the developing plant resulting in production of structural proteins; these proteins thicken the cell walls and give the plants a stronger stem. Many commercial tomato and pepper seedling producers use brushing to toughen their plants. You can simulate this by gently running your hands over the tops of the seedlings. And that just feels good, so do it frequently!

There may be snow on the ground, but it is time to start thinking about gardening, and seed starting is a great way to get that gardening fix. But take the time to plan out your seeding so you have the best success possible for your efforts.

Some seeds will germinate in 3 days, others may take 3 weeks.

Some seeds will germinate in 3 days, others may take 3 weeks.