Understanding the information on a seed packet then knowing how to start seeds are the first steps to a successful garden.
There are three important components to indoor or outdoor seed starting: consistent moisture (never let the seed dry out during germination), soil temperatures between 65 and 85 degrees, and bright light.
Seed starting instructions and tips are on the backside of a seed packet. Some seeds need light to germinate; for example, some peppers and dill just barely need to be covered, so they germinate better with light. Most other seeds need darkness and completely covered by soil. The packet should state what is needed.
A light seed-starting soil mix for germination is best. Never use garden soil. Garden soil is too heavy and may contain weed seeds and pathogens that will harm a newly sprouted seed. Use a commercial seed starting mix or make your own. To make your own, use a large plastic tub with a lid to help keep the soil moist. Mix a ratio of 1-to-3 perlite to sphagnum peat moss good-quality potting soil and stir well. Do not add fertilizer or manures. Dampen, but do not soak, the seed starting mix with warm water.
Seeds can be started in any type of container, from deli salad bowls to Styrofoam cups; special seed trays are not required. If the container has a lid all the better for keeping moisture in; otherwise, cover with clear plastic. This cover creates a mini-greenhouse to help keep the soil moist until the seeds sprout.
Fill the container three-quarters full, plant the seeds according to the depth recommended on the seed packet, water lightly, and cover.
Keeping the soil warm pre- and post-seed germination is important. You can use seed starting heat mats or a warm place in the house. Some seeds need warm soil in the range of 80 degrees to germinate. Vegetable seeds may rot in too cool a soil.
Plants need full sunlight after germination to prevent them from getting leggy (long, thin stems). A grow light or a sunny windowsill can be used once they are up. The goal is to have thick stems and a short distance between sets of leaves. Make sure the seed starting containers are turned every few days so plants don’t grow in one direction.
Seedlings may need transplanted to a larger pot once there are two or three sets of true leaves. Carefully remove them from their containers and place in the next bigger size. Some plants don’t like to be transplanted and are very delicate to handle, such as squash and pumpkins; plant them in a big enough pot they can stay in until planted in the garden.
Best vegetables to start indoors are tomatoes, peppers, squash, eggplant, okra, watermelon, sweet corn, cauliflower, broccoli, cabbage, cucumbers, and herbs.
Vegetables that don’t like to be started early or transplanted are carrots, beets, lettuce, onions, radishes, sweet potatoes, peanuts, green beans, peas, and most leafy greens. Direct sowing into prepared garden soil is best.
How to read a seed packet
The back of a vegetable seed packet will provide days to germination and days to harvest. Here are what all the numbers mean.
Days to germination – The seed will germinate in a given time under the proper growing conditions (warm soil and proper moisture). Some seeds can take a couple days, others a couple weeks.
Days to maturity or harvest – Once planted and allowing for transplant shock, then under proper growing conditions, when you harvest that first fruit or vegetable. Here’s an example.
Amana Orange Tomato seed packet information:
- 7-15 days to germination
- 14 days to transplant size
- 14 days for plant to adjust to soil
- 80 days to harvest
- Total: 115 to 123 days to harvest vegetable
Wyoming’s growing season can be as short as 90 days or as long as 120. Count backward from the 123 days to figure out when to plant. You need to start the seed in early April and transplant the last week of May if you want tomatoes mid-summer. Any days to harvest over 70 makes growing in our environment difficult.
Catherine Wissner is the University of Wyoming Extension Laramie County horticulturist and can be reached at 307-633-4480 or at firstname.lastname@example.org.