Seeds are uniquely adapted to a plant’s natural environment. Therefore, each seed has specific requirements that it needs to turn into a plant.
Some seeds have very broad requirements, and come from plants that gardeners often call “easy to grow from seed.” These seeds are not fussy, and are good for beginners and children. Marigolds and peas are two classic examples of seeds that are often grown in children’s classrooms or given to a child starting his first garden. All one needs to do to grow them is to follow a few basic rules – plant them at the right time (if planting outdoors), and give them light and water.
Many seeds, however, are far more specific in their requirements and much stronger in their preferences. Here are some of these requirements and preferences:
- Light: Some seeds, such as the heirloom flower Salpiglossis, need darkness to germinate. Other seeds, such as annual poppies (Papaver spp.), have the highest germination rate if sown on bare ground or with the lightest of soil coverings.
- Temperature: Many seeds prefer the soil be at a certain temperature, some so strongly that they will not sprout otherwise. Tomatoes and peppers are two classic examples of this. Many people grow their tomato and pepper seedlings on a heating mat, a radiator (as long as it is safe), or the top of their fridge because they do so much better when the soil is warmer. Other seeds prefer that the soil be cool and will be less likely to sprout, or not sprout at all, if the soil is too warm. Many cool-weather crops and flowers, such as garden peas, fall into the latter category.
- Cold period: Some especially finicky seeds prefer, or need, to go through a period of cold weather to germinate. These are the kinds of seeds that are best sown outside in autumn or early winter in cold-weather climates. The North American native butterfly weed (Asclepias tuberosa) is one example of a seed that has a higher germination rate when it has gone through a period of cold weather. Botanists typically call this “cold stratification” or “seed stratifying.”
- Water: Most seeds are more likely to sprout if consistently watered (but not waterlogged) until they sprout, and for a minimum of a couple of weeks after sprouting. However, certain seeds prefer the soil be fairly or quite dry, and other seeds prefer a soggy soil. As one may guess, certain water/bog plants and certain desert plants produce some of the most common seeds to have unusual water requirements.
There are many books that detail the needs and preferences of each type of seed. Two of the most popular ones are The New Seed-Starter’s Handbook by Nancy Bubel and Seed to Seed by Suzanne Ashworth.
Here are a few more things to keep in mind when starting seeds:
- Air circulation: A common problem for novice seed-starters is to sow seeds too closely together or not thin seedlings enough. The spacing between both seeds and seedlings is important to the health of the plants. Seedlings that are too close together are more susceptible to “damping off” (a potentially fatal and very common problem) and other diseases, molds, and mildews. In addition to being sure to sow seeds far enough apart and to thin seedlings if they grow closer together than expected, many gardeners find it beneficial to blow a small desk fan on their indoor seedlings for an hour or two a day after they reach a few inches in height.
- Light: Be sure that indoor seeds have enough light. Place them in a sunny location or invest in a high-quality bulb.
- Hardening off: “Hardening off” is a term gardeners use to signify the period of time when they are getting indoor seedlings adjusted to life outside. Many gardeners are tempted to move indoor seedlings straight outdoors into their garden beds, but the seedlings are much more likely to succeed in the garden if they are allowed to gradually acclimate to outdoor life. Start out by putting them outside for a couple of hours a day, gradually increasing the time. After doing this for at least a week or two, start leaving them outside in a shady spot most or all of the time. Then plant them in the garden, knowing the seedlings have been given the best start possible.
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