Seed Starting Tips

If you’ve ever seen a volunteer tomato, dill or squash seedling pop up unexpectedly in your garden plot, you may think that starting seeds is as easy as dropping them in the soil and waiting. And it is – given the right temperature, moisture, soil, and passage of time. But getting those factors -or germination conditions- just right, and on your schedule can be a challenge.
For grewbies (gardening newbies), we generally recommend that you start with purchased seedlings and some easy-to-sow seeds such as zucchini, radishes, and beans, which can be sown directly in your garden plot.
When you’re ready to take the next step and start seeds indoors, keep these factors in mind:
  1. Seeds need warmth (usually room temperature, though seeds like peppers and tomatoes like it a little warmer) to germinate.
  2. Seeds need continuous moisture to germinate.
  3. Seeds do best in sterile seed-starting mix and clean planting containers.
  4. Once sprouted, seedlings need a very strong source of light to prevent legginess (thin, weak stems and tiny leaves). Windows with a southern exposure in spring in Chicago generally do not allow enough light in, even if they seem very bright and houseplants do fine in them.
  5. Seedlings benefit from a window fan on a low setting (this helps them develop stronger stems and helps inhibit some fungal diseases).

Seedlings under T5 grow lights with an oscillating fan a few feet away. Photo by Breanne Heath. 


More about lighting: 
  1. Once you’ve started your seeds, put your containers pots under a strong source of light. In Chicago, not many home windows allow strong enough light to enter for seedlings, leading to long, spindly plants. These plants have weak stems that can break as soon as they go out into the Chicago wind. Instead, place your plants under inexpensive fluorescent lights – either tubes or compact. Just be sure that the bulbs have a high number of lumens and ideally, a wide range on the light spectrum. Now here’s the part that may seem a little odd – put your lights just 2-3″ above your plants. Getting your seedlings as much light, as close as possible will help them grow into squat, multi-leaved, healthy plants.
  2. As your seedlings grow, raise the fluorescent fixture as needed to give them a few inches of space from the bulbs. It is also a great idea to keep a fan on low, blowing on your seedlings.  Do this after they sprout, and the fan will mimic the wind they would experience outside. As the stems sway in the gentle breeze, they will develop thicker and stronger – and be better able to withstand our very windy spring days. When your plants are 4-6 weeks old, and the last frost date has passed (usually around Mother’s Day), it’s usually safe to plant them outside in the garden.
For more information on starting seeds under light indoors, check out The Garden Primer by Barbara Damrosch, in the chapter “What Plants Need”.
written by Breanne Heath