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Successfully Starting Seeds Indoors


Photo by Fotolia

Gardening from seed has several benefits. When you garden from seed, you have more varieties available to you, you know what’s going into your food because you are growing it, and you’ll save money by purchasing seeds rather than plants.

Why start seeds indoors?

Some varieties are best started indoors because you have more control over the growing conditions. Starting seeds indoors extends your gardening season, allowing you to grow varieties that require longer growing times than your area’s natural growing season allows. In the case of perennial flowers, an early start can reap first year blooms.

When is the correct time to start my seeds indoors?

Botanical Interests uses the average last frost date—identified as the first day in spring when there is less than a 50 percent chance a frost will occur—as a guideline for when to sow seed. It’s also helpful to know your average first frost date in the fall so you can determine the number of days in your growing season, as well as plan your summer and fall sowings.

How do I start my seeds indoors?

Containers and trays: Almost any container can be used to start seeds including milk or egg cartons, yogurt cups, or plastic trays. When reusing any container, it should be clean and sanitized, and have holes in the bottom that allow excess water to drain. For easy transplanting, try sowing seed in a biodegradable paperboard, paper or pulp pot that can be planted directly into the garden.

Labeling: Don’t forget to label as you sow. Garden stakes, craft sticks or writing directly on pots using paint marker all work well.

Media: A high-quality seed-starting mix (media) is loose and lightweight, holds moisture, and is free from sticks and bark. Avoid potting soil mixes, which can be too heavy for tiny seeds, or soil from your garden, which may introduce insects, weeds or diseases. Thoroughly moisten media before filling your container.

Moisture: Covering your containers with a clear lid or clear plastic wrap helps retain moisture and increase humidity during germination. After seedlings emerge, remove the cover. Misting using a spray bottle or bottom watering (adding water to the drainage tray) are great ways to keep growing media moist without disturbing seeds and young seedlings. Check moisture regularly to prevent seeds and seedlings from drying out or from sitting in standing water.

Temperature: Optimal media temperatures for seeds to germinate will vary for each variety. Once the seeds germinate, room temperatures of 70 to 75 degrees will help most seedlings grow best. Warm season plants such as tomatoes, eggplants and peppers appreciate warmer soil conditions and may benefit from the use of a seedling heat mat when sown indoors.

Light: For best growth, seedlings need at least 14 hours of light per day. Even your sunniest window likely will not supply enough light to grow strong plants. For an efficient and inexpensive option that provides adequate light, we recommend using a shop light with cool or a mix of cool and warm fluorescent bulbs placed 1 to 2 inches above seedlings. To make it easier, plug your lights into a timer set to turn on and off automatically.

Circulation: Air circulation around seedlings can help prevent disease problems while strengthening seedlings. A fan on low setting will create adequate airflow. Avoid aiming the fan directly at the soil as it can cause rapid drying.

Fertilizer: If your seed starting mix does not contain nutrients, add a diluted amount of slow-release, organic, balanced fertilizer to the media or use a liquid formula once seedlings have true leaves. “Balanced” fertilizers have equal amounts of nitrogen, phosphorous and potassium, represented on packaging respectively as numbers with dashes between (e.g. 20-20-20). Check the label for instructions on diluting the fertilizer, and the recommended frequency and rate to mix for seedlings and transplants.

Hardening off: “Hardening off” is the 7- to 10-day process of acclimating indoor seedlings to outdoor conditions. The hardening-off process reduces transplant stress and the chance of sunburn, which both negatively impact overall performance and yield. Start by placing plants in a protected, shady area, progressing to more sun  each day (for sun-loving varieties) over the 7 to 10 days. Be sure to bring plants in at night if temperatures drop below 45 degrees. After 7 to 10 days, plants will be ready for transplanting. Before transplanting, consider fertilizing with seaweed or kelp to further reduce transplant stress. Transplant on a calm, cloudy day, in the evening, or use row covers to buffer wind, sun and temperature swings. Most warm season plants perform best when transplanted in soils over 45 degrees.

Gardening from seed is very rewarding. On the inside of every Botanical Interests seed packet you will find the best growing conditions for the variety. They provide information about special care, organic gardening methods, and tips to improve your garden throughout the seasons. Use Botanical Interests' garden journal templates and lists to help you keep track of which seeds you started and when. By following these guidelines and keeping a journal, all that’s left to do is watch your seeds grow into productive and healthy plants!