Starting seeds indoors


Starting seeds indoors

Varieties such as tomatoes, peppers, onions, perennials, and some annual flowers really benefit from an early start indoors if you live in an area that has short warm seasons.  For those in Southern California, it is helpful to those in areas of high elevations or zones outside of nine and ten. 

Here are our tips if you are going to start your seeds indoors.


Providing adequate light is the most important step in growing healthy seedlings. Long, tall, skinny seedlings that may fall over are usually the result of not enough light. Use fluorescent light, preferably a 4-tube ballast. Tubes must be placed 1” – 2’ above seedlings. Ballast can be hung on chains and hooked into ceiling hooks for easy adjustment as seedlings grow. The seedlings should receive at least 16 hours of light per day.


Purchase a high-quality seed starting mix that holds moisture yet has good drainage. You will increase your success rate if you use appropriate seed starting soil.


 Soil must be kept moist but not soggy. If soil completely dries out, the seedlings may die. If soggy, disease problems may affect seeds or seedlings. You will notice mold forming on the soil which can be detrimental to the plant. 

What to plant your seedlings in

 Almost any container can be used to start seeds including milk or egg cartons. Punch holes in bottoms to ensure adequate drainage. Seed starting trays and larger pots for transplanting seedlings are available. To keep the soil moist until seed germinates, cover container with a clear lid or clear plastic wrap. Remove cover when seedlings begin to emerge. If your containers are very small, and it’s not yet time to plant your seedling outside, you may need to transfer them to larger containers to allow for proper growth. Choose a container twice the size of the original one, fill it part-way with moistened potting soil, and carefully transplant the seedling handling by the root ball or the base of the stern. Add soil to fill, and water gently.

Why you should harden off your seedlings

Harden off the seedling for about a week by taking containers outside and placing in a filtered sun/shade location away from harsh winds during the day. Gradually increase time outdoors. This process is very important for the plant to acclimate from the conditions inside to the outside. Do not place your seedling in a high wind area or on hot concrete. Make sure to check your seedlings often.

When to sow seeds

All packets indicate the optimum sowing time based on the average last spring frost date. For Zones 9 and 10 you can look for information on what season to grow your plants in. Warm-season (May-Oct) and cool season (Nov-April)


Generally, tomatoes are sown indoors 6-8 weeks before the average last frost, peppers 8-10 weeks, onion 8-12 weeks. Flower seed sowing time can vary from 4-12 weeks before the average last frost depending on the variety.  


 Warm-season crops such as beans, cucumbers, melons, pumpkins, squash, and watermelons are frost-sensitive and should be sown after the average last day of frost in your region. Cool-season crops such as carrots, lettuce, peas, radish, chard, and many leafy greens can be sown as early as 6 weeks before the average last frost for spring harvest, and in late summer for a fall crop. Most annual flower seeds are sown around the average last frost date even though some can be 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 the seeds to germinate.

When is your average last frost?

Knowing the average last day of frost in your region is crucial when planting a garden and being an expert grower. To find out your last day of frost, call your county Cooperative Extension Service. You can also consult websites like:

Perennial vs. annual

A perennial is a variety that regrows from the root system every year. The advantage of perennial is that it doesn’t need to be replanted 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 a longer period of time. Annuals do not regrow from their roots every year; they may produce seed that will germinate and grow the following year. Annuals usually bloom for a longer time period than perennials – in many cases, they bloom most of the growing season (spring to late fall).

Common Challenges and our Solutions

Getting the best seed germination

Occasionally, seeds may fail to germinate. Common reasons 

 – seeds are sown too early when soil temperatures haven’t warmed up enough

–  seeds are not sown at the recommended depths, too deep or too sallow

– seeds are not kept consistently moist 

– unusually cool or wet weather occurs. 

Build better garden soil

Adding organic matter such as compost or manure to your garden soil will help create healthy soil. Don’t over-fertilize your vegetable garden but do make sure you feed your vegetables. Refer to the fertilizer instructions. 

Space your plants correctly!

Spacing between plants is important for proper development. Proper spacing allows for adequate sunlight, air circulation and room for roots to grow without competition.

Monitor for diseases

Many plant diseases can be prevented by starting with high-quality fresh seeds and good gardening practices. This includes good garden hygiene like removing diseased plant material from the garden.

Prevent and monitor for pests

Pest information can be found on the UC IPM website in great detail.

Give adequate sunlight

 Most vegetable plants need at least 8 hours of direct sunlight. Some root crops (carrots, beets) and leaf crops (lettuce, kale) can manage with 6 hours of direct sun.  If plants are not grown in optimal conditions it is likely they will have pest and disease issues. 

Control weeds

 Weeds compete with seedlings and desirable plants for water, light, and nutrients. Also, they can harbor harmful insects and diseases. Keep flower and vegetable beds weeded all season, particularly during initial seedling emergence. 

Retain Moisture

 Mulch is a layer of almost anything – grass clippings, leaves, bark, newspaper – placed on the surface of the soil in order to maintain even soil moisture and prevent weeds from coming up. Mulching is critical in dry regions., particularly in zones 9 and 10.  Mulch should be applied thickly, several inches if possible, to keep weed seedlings from emerging. When using leaves and wood mulch, these items break down and improve the soil over time in addition to keeping moisture in the soil. 

Once you have mastered a few of the basic steps of seed gardening you will realize the potential you have to create a beautiful and bountiful garden with local, organic seeds!

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