Starting Vegetable Seeds: A Concise Guide

Starting Vegetable Seeds: A Concise Guide

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by Ann Clary and C. Darren Butler

Why start your own seeds?

Better selection. Availability of seedlings may be painfully limited at local garden centers, and they don’t always stock the best varieties for your area or the particular variety that suits your needs. Many new varieties, heirlooms, and disease-resistant varieties, such as mildew-resistant zucchini, that might produce well or offer other benefits in your garden must be started from seeds.

Healthier Plants. When started from seeds, plants adapt to your soil and current environmental conditions such as temperature, sunlight, and soil moisture. Purchased transplants may be root-bound when still small, and never produce well.

Avoid Chemicals. Start your own seeds and you can be sure that your vegetable plants are never treated with pesticides or chemical fertilizers.

Cheaper. Starting from seeds is usually the the most economical option for any vegetable. This may vary based on many factors as compared to purchasing starts from your local garden center. Do you already have seed starting materials? Are you starting many seeds for a large crop or do you just need 1 or 2 plants?

Learning and fun. See new life emerge from the soil as seeds germinate, watch starts grow under your care, and learn from what works and what doesn’t.

Remember—some vegetable plants dislike root disturbance and don’t transplant well; they should be planted directly in the soil, not transplanted from seed containers. Root vegetables, such as carrots and beets, many cucurbits such as squash and melons, and legumes such as peas and beans among others typically are not good candidates for transplanting and should be seeded directly into prepared soil.


Starting vegetable seeds at the right time of year in Southern California is important for optimal plant health, and abundant harvest. Plant too early and some vegetables may suffer in cold late-winter or spring weather. Plant too late, and the plant may not mature or produce a harvest before the heat of summer arrives.

To start seeds you’re a going to need a few—but not many—supplies.


GardenZeus recommends open-pollinated, untreated, organically grown seeds. For additional information on choosing seeds for your area, see How to Choose the Best Seeds for California Gardens and Common Terms for Seeds and What They Mean.


Seed starting containers range from repurposed home items to specialized seed trays.

Repurposed home items save money but may be awkward or less than ideal for seed starting. Plastic containers and milk cartons aren’t biodegradable and might no longer be recyclable once modified for seed starting. Homemade paper and cardboard containers tend to fall apart from moisture. Eggshells and egg cartons may also break or fall apart, and soil may dry out quickly in any small seed-starting container. Small clay flower pots are awkward or inefficient for starting large quantities of seeds, although they can be a solution when starting a small number of seeds.

GardenZeus does not recommend either peat pots or peat pellets often sold at garden centers. Plant roots do not necessarily penetrate the bottoms of peat pots and the individual containers dry out quickly. Peat pellets are expensive and cannot be reused. And most importantly, harvest of peat moss causes environmental damage to wetlands, reduces capture of carbon from the atmosphere, and accelerates climate change.

Six-pack seedling containers are an inexpensive option. GardenZeus recommends cells that are at least 2 inches deep for sufficient root space and better moisture retention.

Flats are preferred by many gardeners for organizing and managing six-pack cells, especially indoors or anywhere water can’t drain freely, and are reusable almost indefinitely.

Seed Starting Mediums

Seed-starting mediums are NOT the same as healthy soil.  Seed-starting mediums do not have to be fertile or rich in nutrients, but they do need to be loose enough to work with easily and allow for aeration (air flow between the soil particles). Ideal seed-starting soil will retain moisture but not get waterlogged.

Gardeners can use formulas or purchase commercial potting soil mix. GardenZeus recommends a mix of 1/3 washed sand, 1/3 compost, and 1/3 soil from your garden. If soil-borne disease or insect pests have been a problem, sterilize garden soil by baking in an oven for 20 to 30 minutes at 200 degrees before adding sand and compost. Sterilizing soil also kills weed seeds—and kills the microbial life that is so important to plant health and vigor. Experienced seed-starters often formulate their own mix using combinations of any of the following: horticultural vermiculite, perlite and filtered garden soil or sifted compost. Many gardeners prefer to avoid using perlite or vermiculite in their seed-starting mixes; both vermiculite and perlite require significant energy to produce. In addition, other products, such as coir or recycled paper fiber, are perceived as from reusable or renewable resources.  Commercial seed-starting mixes may be convenient or preferred by many gardeners.

Regardless of using a homemade formula or commercial mix, GardenZeus recommends that gardeners avoid using peat moss (see “Containers” above).

Preparing Seeds

Keep in mind that some seeds benefit from presoaking while others may benefit from presprouting. See specific plant information for more details.


GardenZeus recommends moistening or presoaking the seed starting soil or medium before planting. If planting in flats or directly outdoors, place the individual seeds according to the recommended spacing for each plant. Many gardeners prefer to plant several seeds per compartment in six packs and thin to the single strongest seedling. A reasonable rule of thumb is to cover seeds to a depth of 2 to 3 times their diameter or width (the smaller dimension when a seed is placed on a flat surface). If planted too deep, seedlings might be slow to emerge or have difficulty growing to the surface. If planted too shallow, seeds may be prone to drying out or produce an exposed or weaker root system.

After planting GardenZeus recommends covering seeds with sand, light potting soil, or seed-starting medium and misting or watering.

To optimize seed germination, provide sufficient and consistent moisture and proper temperature.


Most vegetable seeds germinate well in warm indoor areas at about 70 to 85 degrees. Some seeds need limited or specific soil temperature for best germination. Bottom heat can work wonders for improved germination. Many gardeners use heated seed-starting mats below their trays. Remember, it’s the soil temperature that matters, not air temperature.


Keep the planting medium moist but not wet. Depending on size and age of seedlings, texture of the soil or planting medium, humidity, and temperature, this may require misting or watering as many as several times per day. Some commercial seed starting systems use a cover to increase humidity, retain moisture, and reduce watering frequency.

Other commercial products contain a continuous self-watering system to ensure that the seeds receive continuous moisture.

Grow lights can help to provide the abundant light indoors that seedlings need, especially when seedlings will be grown for days or weeks before transplanting. Grow lights have little or no effect on germination, but they can be help to support healthy and vigorous growth after seedlings emerge.

GardenZeus has customized growing information by plant and zip code. To get started, enter your zip code here.

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