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Sowing or Starting Seeds

Many types of planting mediums can be used when sowing or starting seeds. The seeds can be planted in artificial mediums like vermiculite, soilless organic mediums like peat moss, or amended soil mixtures. Such mediums should be fine, uniform, and loose. The medium should be low in fertility or soluble salts. Planting mediums should be free of insects, disease, and weeds. It should be capable of retaining moisture. A mixture of sphagnum peat moss and vermiculite provides such a mixture and can be purchased commercially or easily made. Do not use garden soil to start seedlings.


There are many options when it comes to containers for sowing seeds. You can buy plastic or wooden flats and trays. You can make your own flats and trays. You can use flowerpots. Or you can make containers from things like plastic yogurt cups, the bottom halves of milk cartons, bottom half of water bottles, etc. so long as they are thoroughly cleaned with a mixture of one part chlorine bleach and nine parts water and holes are punched in the bottoms for good drainage.


Proper planning should be done when sowing seeds indoors for transplanting outside. When to plant depends on several factors, including how fast germination occurs, the growth rate of the plants, and the conditions under which the plants are being cultivated. Typically, this falls between 4 and 12 weeks before the last freeze of spring.

After determining the proper time to plant, you must prepare you containers for seeding. Fill the container with moistened medium to within 3/4th of an inch from its top. If you are planting very small seeds, make sure the top 1/4th inch is vermiculite or some other finely screened mixture.

Very fine seeds should not be covered, but instead lightly pressed into the planting medium or sprayed with a fine water mist after being placed atop the planting medium. These can be broadcast, but care should be taken to create a uniform stand of plants by first broadcasting in one direction and then the opposite direction.

Medium to large seeds are often sowed in farrows about 2 inches apart and 1/8th to 1/4th inch deep which aids with the availability of light and movement of air once the seedlings sprout. This also slows the spread of damping-off fungus should it appear. Once planted the seeds should be lightly covered with dry vermiculite or finely sifted medium if they require darkness to germinate. Often, 2 or 3 large seeds are planted in an individual small contained so they can later be thinned, allowing the strongest seedling to continue to grow.

You can also purchase seed tape at most garden stores. They offer different tapes for both indoor and outdoor planting. The seed tape is enclosed in an organic, water soluble material with the seeds inside evenly spaced. Once planted, the organic, water soluble exterior dissolves allowing the seeds inside to germinate as normal. While seed tape is more expensive per seed than packaged seeds, tape does provide several benefits like proper spacing of seeds and ease when sowing in straight rows.


Seeds can also be pregerminated by sprouting the seeds prior to planting in pots or a garden. This reduces the time required to germinate and ensures a high germination percentage because of the temperature, moisture, and other environmental factors are easily controlled.

Pregermination is done by laying the seeds between a folded cotton cloth or paper towel on vermiculite or like material and keeping it moist and warm. When the roots begin to emerge, plant the seeds in individual containers or directly in the garden being very careful not to damage the tender roots. Plant them at half their recommended depth, cover with a little potting mix, and then add about 1/4th inch of vermiculite or milled sphagnum peat moss to keep the surface moist while remaining light enough for the shoot to push through.


Once seeds are sown, the planting medium should be thoroughly moistened using a fine mist sprayer or by placing the container inside some type of tray that contains about an inch of warm water. Be sure not to splash or otherwise do anything that might displace small seeds. Once the container has been thoroughly watered, set it aside to drain.

Seed flats should typically not require additional watering during germination. One way to avoid the need for additional watering is to place the flat or container into a clear plastic bag after its initial watering keeping the plastic 1 to 1 ½ inches above the soil. Some home gardeners place glass or plastic wrap over their flats instead of using a bag. You can also purchase commercial clear plastic domes to place over flats. Avoid direct sunlight so that temperature inside the bag or other cover does not rise to the point where it harms the seeds. Remove the plastic bag or cover as soon as the first seedlings appear.

Temperature and Light

During germination, the planting medium containing the seeds should be kept at the plant’s optimum germination temperature. Because this is usually higher than the typical temperatures in your home at night, it is often necessary to use thermostatically controlled heating cables or mats to maintain a steady optimum temperature during germination.

After the seed has germinated and the seedling has established itself, the container or flat should be moved to a location that is cool, bright, and has good air circulation. Typically, daytime temperatures at this location should be 65° to 70° F, and evening temperatures should be 55° to 60° F. However, this may vary by plant variety. Some may have different optimal daytime and evening temperature ranges. Others may do best at a steady temperature.

It is important that seedlings get receive bright sunlight immediately after sprouting, so that it can begin producing its own food with photosynthesis rather than using stored food from the seed’s endosperm or the cotyledons. If there is not a good place where the plants can get bright sunlight, place the seedlings under a 40-watt, cool white fluorescent light positioned 2 to 4 inches above the seedlings for 16 to 18 hours per day. As the seedlings grow, continuously raise the lights so they remain 2 to 4 inches above the plants.