Anxious for spring to come, northerners and other gardeners living in cold climates can get a jump start on the growing season by starting seedlings in the winter, grown indoors from seeds that germinate in containers. One key to growing successful seedlings is timing. By starting them too soon, you risk the seedlings outgrowing their containers before spring. On the other hand, starting too late is risky, as they won't be ready for transplanting when spring comes. That's why it's necessary to monitor your area's weather as well as know the needs of different seedlings.
Seedlings are newly spouted young plants or trees with a single stem, lacking branches. They can either be grown in the ground when there's no danger of frost or in containers inside buildings, homes or greenhouses.
Parts of a Seedling
A seedling is composed of three basic parts: the radical, the hypocotyl and the cotyledon. With favorable growing conditions, the radicle is the first part of the seedling to sprout. Later the radicle, which is the embryonic root, evolves into the primary root, where lateral roots and root hair will develop. After the radicle emerges, the cotyledon appears.The cotyledons are seed leaves, making up the major portion of the embryo. The embroyonic shoot, called the hypocotyls, later develops into the stem. The hypocotyls is separated externally from the root by the collet. The embryo is encased by the seed leaves and cotyledons, which usually differ in shape from the leaves produced from the mature plant. Plants producing one cotyledon are grouped as monocotyledons, while plants yielding two seed leaves are dicotyledons, also known as dicots. After a seedling matures into a plant, adult leaves appear, called metaphyll.
Cryptocotylar seedlings, also known as hypogeous, are seedlings with the cotyledons remaining within the seed. This seedling usually remains below ground. Phanerocotylar seedlings (epigeous) are types of seedlings in which the cotyledons grow inside the seed and usually emerge above ground.
The same conditions are needed for growing indoor seedlings as those grown outdoors. However, growing seedlings inside requires more care because you need to artificially maintain the environment. Although special considerations apply to individual cases, soil, light and water are the basic needs of growing indoor seedlings, just as any plant grown outside.
Seeds sown too closely together can result in seedlings that are spindly. That's because there are too many plants competing for light, resulting in seedlings that are long and leggy, unable to support themselves. To prevent spindly seedlings, sow seeds with enough room between them for proper growth. However, if you've already planted them too thickly, remove the seedlings from the original pot and replant in separate containers, planting them deeper within the soil.
Gradually transfer seedlings from a warm environment, such indoors or a heated greenhouse, so they can slowly adjust to colder temperatures. First, make sure there's no danger of frost. Transport seedlings outside for only a brief period each day, returning them, covered, to their original home at night. Do this, gradually increasing the time outdoors, for about two weeks. Then, it's safe to transplant seedlings into the ground.
Usually labeled "sprouts," seedlings are also eaten as health food. However, their nutritional worth is over-rated because the small size of a seedling doesn't yield enough vitamins and minerals to warrant the nutritional claims made by some health enthusiasts.