Starting Seed Like a Pro - U of I Extension

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Starting Seed Like a Pro

This article was originally published on February 14, 2017 and expired on June 4, 2017. It is provided here for archival purposes and may contain dated information.

Starting Seed like a Pro


BLOOMINGTON, Ill. – University of Illinois Horticulture Educator, Kelly Allsup, states there are added benefits to starting your garden seed indoors. Garden seed started indoors has a higher germination rate, produces more uniform growth, more cost efficient, can offer a better selection and gives you a jump-start on the growing season.

Starting seed can be very easy if you remember the three requirements of seed germination: water, oxygen, and temperature. Water breaks the seed coat, allowing oxygen to enter as the seeds necessary respiration in this step. Respiration is required to allow the cotyledon (shoot) to access the stored energy in the endosperm (stored energy in the seed) therefore allowing growth. Temperature plays a substantial role in seed germination because the seed will not germinate under temperature extremes. Please follow these steps for successful garden seed germination.

  1. Choose a location to germinate and grow your seedlings. This spot can be in front of a south facing window in your home, in a cold frame or a greenhouse. Cold frames can be purchased from garden centers or easily made out of lumber and plastic.
  2. Choose seeds and read the germination requirements on the back of the package. Some seeds germinate faster than other seeds. This information is crucial when timing your plants to be ready for the garden. For instance, cucumber, melon, squash, radish, beets, herbs and peas germinate faster than broccoli, cabbage, pepper, tomatoes, eggplant and Brussel sprouts. The amount of time to seed germination rate also depends on temperature.

3.     You will want to gather supplies needed to start your seed. A plug tray, plastic inserts in a flat that you may have left- over from buying plants or peat pots are the best vessels to start seed. Fill trays with a high-quality germination mix composed of peat moss, vermiculite and/or bark rather than average garden soil to ensure good drainage. Use fluorescent lighting mounted over the seed trays or heating pads placed under the seed trays to reach optimal temperature for seed germination. Use a spray bottle to water plants while they are young.

  1. Pack trays with the germination mix by tapping the tray on a hard surface to ensure all air spaces fill.
  2. Use your finger to create an indention in the soil. Place 1-2 seeds in the divot. The general rule of thumb is to bury the seed the same depth of the size of the seed; 1:1. This information will also be on the seed package for reference. Then either sprinkle a thin layer of germination mix over or push seed down with the tip of a pencil.
  3. Finely mist the soil with water until media is saturated. You can also saturate mix before seeding.
  4. Cover with glass or clear plastic tucking under the sides of the plug tray to help ensure moisture & warmth at all times. Germinating seeds must be kept moist. Remove plastic daily and only spritz the cells that have dried out.
  5. Place the plug tray on heat mats or under lights to emit extra heat. The optimal temperature for germinating seed is 77-86 degrees. Use a thermometer to determine the temperature of your rooting media.
  6. Once you see that at least one seed has germinated, remove plastic or glass to prevent damping off (fungal disease) of young seedlings.

Congratulations, you have germinated seeds like the professionals. However, there is more to know to make sure this new seedling makes it to the garden in good health. Please follow the following steps for successful garden seedling care.

  1. New seedlings need light. The fluorescent light you originally had to heat the seeds will now provide light for photosynthesis. The best indoor light situation is the combination of natural light from a south facing the window and the addition of fluorescent lights. Place fluorescents 6-8" above the seedlings.
  2. Once all of the seedlings have emerged, remove plug flat from the heating mats.
  3. Use the water sprayer to individually water dry cells to help prevent overwatering. Water flat thoroughly if it is light when held.
  4. Once first leaves are on the seedling, fertilize with weak fertilizer (1-2 tsp. per gallon of water) using a watering can that is designed to make the water trickle out. Fertilize additional times if plants are slow to start, or nutrient deficiencies are evident.
  5. Be conscientious of timing. Our last frost-free date in Zone 5B is April 15. Cool weather vegetables can be planted earlier but covered if a frost returns. Most seeds take 7-10 days to germinate and 2-8 weeks to grow in their plug flat before planting in the garden. This amount of time varies with temperature, light, and overall type of garden seed.
  6. You will want to harden off the plants by placing them outside for a few days before planting. This timing, allows your plants to acclimate to the environment.

Now you are ready to plant your vegetable garden and enjoy the fruits of your labor when the time comes. 

Source: Kelly Allsup, Extension Educator, Horticulture,

Pull date: June 4, 2017