How to Start Seeds Indoors

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If you’re learning how to start seeds indoors, consider varieties of tomatoes, peppers, onions, perennials, and some annual flowers. These crops can benefit from an early start indoors, especially if you live in an area with short, warm seasons. Starting seeds indoors helps individuals who garden in high elevations or areas with erratic weather patterns.

Light Requirements for Seeds Started Indoors

Providing adequate light is the most critical step in growing healthy seedlings. Long, tall, skinny seedlings that tend to fall over are usually the result of not enough light. To help the seedlings get enough light, you can use fluorescent light(s), preferably a 4-tube ballast. Place the lights 1” – 2’ above the seedlings. They can be hung on chains and hooked into ceiling hooks for easy adjustment as seedlings grow. Seedlings should receive at least 16 hours of light per day.

Seed Starting Soil for Seeds Started Indoors

Purchase a high-quality seed starting mix that holds moisture and has good drainage. As a result of using an appropriate seed starting mix, you will substantially increase your success rate.

How Often to Water Seeds Started Indoors

Seed starting soil mix must be kept moist but not soggy. If the soil becomes completely dry, the seedling(s) will likely die. On the other hand, if the soil becomes too saturated, it could result in disease problems for the seeds or seedlings. When soil becomes too soggy, it is common to notice mold forming, which can be detrimental to the plant.

How to Plant Seeds Started Indoors

Seed starting trays and larger pots for transplanting seedlings are available. However, you can easily use almost any container to start seeds, such as milk or egg cartons. First, find the container type that works best for you. Second, punch holes in the bottom to ensure adequate drainage. After that, be sure to keep the soil moist until the seed germinates. An excellent way to do this is to cover the container(s) with a clear lid or clear plastic wrap. Once you start to see the seedlings begin to emerge, you will need to remove the cover.

If your containers are small, and it’s not yet time to plant your seedlings outside, you may need to transfer them to larger containers to allow for proper growth. First, choose a box twice the size of the original one. Next, fill it part-way with moistened potting soil. After that, carefully transplant the seedlings, handling them by the root ball. Next, add the soil to fill. Lastly, water gently.

starting seeds in plastic tray

Why You Should Harden Off Your Seedlings

It is important to harden off seedlings because seeds started indoors may take some time to adjust to new outdoor living conditions. It is best to harden off seedlings for about a week. To do this, take their containers outside and place them in a filtered sun/shade location away from harsh winds during the day. Gradually increase their time outdoors. This process is critical for the plant to acclimate from the conditions inside to new outside conditions. Most importantly, do not place your seedlings in a high wind area or on hot concrete. Be sure to check your seedlings often.

When to Start Seeds Indoors

San Diego Seed Company seed packets indicate the optimum sowing time based on the average last spring frost date. As for Zones 9 and 10, you can look for information on what season to grow your plants — in the warm season (May-Oct) or the cool season (Nov-April).

If you live in an area that has frost, check your frost dates here. Generally, tomatoes are sown indoors 6-8 weeks before the average last frost, peppers 8-10 weeks, and onions 8-12 weeks. Flower seed sowing time can vary from 4-12 weeks before the average last frost, depending on the variety. Although it can vary, here is a general list of crops and the number of weeks before the last frost you should start them indoors.

Number of weeks to start indoors before the average last frost date:

Basil: 5 weeks
Broccoli: 6-8 weeks
Cabbage: 8-10 weeks
Cauliflower: 6-8 weeks
Cucumber: 2-3 weeks
Eggplant: 6-8 weeks
Kale: 8-10 weeks
Lettuce: 7-8 weeks
Melon: 1-2 weeks
Onion: 10-12 weeks
Parsley: 10-12 weeks
Pepper: 6 weeks
Pumpkin: 1-2 weeks
Squash: 1-2 weeks
Swiss Chard: 6-8 weeks
Tomato: 6-8 weeks

Planting Seeds Outside

Warm-season crops such as beans, cucumbers, melons, pumpkins, squash, and watermelons are frost-sensitive; sow them after the average last frost date in your region. Cool-season crops such as carrots, lettuce, peas, radish, chard, and many leafy greens can be sown as early as six weeks before the average last frost for a spring harvest and in late summer for a fall crop. Most annual flower seeds should be sown around the average last frost date, even though some can be planted earlier. Perennial flower seeds can be sown almost any time – early spring through late summer. Even a late fall sowing works; seeds remain dormant in the ground until conditions in early spring permit them to germinate.

How to Determine Your Average Last Frost Date

Knowing the average last day of frost in your region is crucial for planting a garden and becoming an expert grower. Find out your last day of frost by calling your county Cooperative Extension Service. Similarly, you can consult websites like the Farmers Almanac.

Perennial vs. Annual

A perennial is a crop that regrows from the root system every year. In contrast, annuals do not regrow from their roots every year. However, there is a possibility that annuals produce seeds that will germinate and grow the following year.

The advantage of a perennial is that you don’t have to replant it every year. A disadvantage is that perennials have a shorter bloom period than most annuals. When choosing perennials for your garden, mix varieties with different bloom periods so that you have color in your garden over an extended period of time. Annuals usually bloom for a longer period than perennials – in many cases, they bloom most of the growing season (spring to late fall).

Why Didn’t My Seeds Germinate?

Here are some common mistakes when sowing seeds both indoors and out.

  • Sowing the seeds too early. For example, when the soil temperatures haven’t warmed up enough.
  • Not sowing the seeds at the recommended depths, for instance, sowing them too deep or too shallow.
  • Seeds are not kept consistently moist. As a result, the seeds dry out.
  • Unusually cool or wet weather occurs.

Once you have mastered a few of the necessary steps on how to start seeds indoors and outside, you will realize the potential you have to create a beautiful and bountiful garden from seeds.

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