Starting Seeds Indoors

Seedlings are fun to grow!
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Gardening from seed has several benefits. There are more varieties available to you, you know what’s going into your food and flowers because you are growing them, and you’ll save money by purchasing seeds rather than plants. But I caution you, it can get addictive! Starting seeds is simple and very rewarding. It is easy to start more seeds than you will need. I do it every year. I end up giving hundreds of seedlings away to local food groups, friends and neighbors. If this is your first time starting seeds, keep it simple and don’t overwhelm yourself with too much to take care of. Think about what you and your family eat the most and start with those seeds. Lettuces and greens are simpler to grow and more immediately gratifying than peppers and tomatoes.

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. With perennial flowers, an early start can reap first-year blooms.

When is the correct time to start my seeds indoors?

Use your average last frost date as a guideline for when to sow seed. This is identified as the last day in spring when there is less than a 50% chance a frost will occur.   Most seed packets will tell you “Start indoors X weeks before last frost”.  This is also generally known as your USDA Growing Zone.  Seed packets will also list dates by zone.  You can identify your zone here. It’s also helpful to know your average first fall frost date so you can determine the number of days in your growing season as well as plan your summer and fall sowings.

Here is a general guideline on how long before your average last frost date to start indoors:

10-12 weeks8-10 weeks6-8 weeks4-6 weeks2-4 weeks
ArtichokeDillBorageBasilBroccoli Raab
CeleryEndiveChiveBok Choy
Some lettuces
Swiss Chard

How do I start my seeds indoors?

Plant Pots are a great place to start seeds.
Plant Pots are a great place to start seeds.

Containers: Almost any container can be used to start seeds including milk or egg cartons, yogurt cups, plastic trays, etc.  We offer a Starter Kit that will help you get going and it is reusable.  When reusing any container, it should be clean and sanitized, and have holes in the bottom that allow excess water to drain.

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

Medium: A high-quality seed-starting mix (medium), is loose and lightweight, yet holds moisture while being free from sticks and bark. Avoid potting soil mixes, which can be too heavy for tiny seeds, or soil from your garden that may introduce insects, weeds, or diseases. Thoroughly moisten medium before filling your container.  I have had a lot of success with our Peat Pellets as there is no netting around them and nothing that needs to break down which could impede how quickly the roots can penetrate into the soil in your final planting location.

Moisture: Covering your containers with a clear lid or clear plastic wrap helps retain moisture and increase humidity during germination. After your 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 medium moist without disturbing seeds and young seedlings. Check moisture regularly to prevent seeds and seedlings from drying out or from sitting in standing water. Our starter kit and 7.5″ dome offer adjustable ventilation to assist with this.

Light: For best growth, seedlings need at least 14 hours of light per day. Even your sunniest window may not supply enough light to grow strong plants. An efficient and inexpensive option that provides adequate light is a shop light with cool-white fluorescent bulbs or a mix of cool-white and warm-white bulbs placed 1”–2” above the seedlings. To make it easier, use a timer that is set to turn on and off automatically.

Temperature: Optimal medium temperatures for seeds to germinate can vary. Seed packet sowing instructions indicate if the temperature is specific. Once the seeds germinate, room temperatures of 70º–75ºF will help most seedlings grow best. Generally, frost-sensitive 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.

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. Our starter kit and 7.5″ dome offer adjustable ventilation to assist with this.

Fertilizer: If your seed starting mix does not contain nutrients, add a diluted amount of slow-release, organic (if possible), balanced fertilizer to the medium or use a liquid formula once seedlings have true leaves. “Balanced” fertilizers have equal amounts of nitrogen, phosphorous, and potassium represented 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.  We suggest always using organic fertilizers.

Hardening off: This is the 7 to 10 day process of acclimating plants started indoors to outdoor conditions. This 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 (for sun-loving varieties) over 7 to 10 days. Bring plants in at night if temperatures drop below 45°F. 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°F.

Garden Tower Project will be providing several more blog posts on hardening off seeds, starting and growing some common vegetables, garden maintenance, pests control, etc. Consider joining our Garden Training Project users group on Facebook to learn more about starting seeds, along with dozens of other topics.

Happy and Healthy Gardening!!!