Starting Your Plants by Seed
Growing your own transplants from seeds indoors can give you a head start on the growing season. In some cases, it may be the only way to obtain plants of a new or special cultivar (variety) that is not widely available through garden centers.
To obtain vigorous plants, start with high-quality seed from a reliable source. Select cultivars that provide the plant size, color (flower, foliage, or fruit), and growth habit you want. Choose cultivars adapted to your area. Many vegetable and flower cultivars are hybrids. They may cost more than open pollinated types, but they usually have more vigor, more uniformity, and better growth than non-hybrids.
Purchase only enough seed for one year’s use, because germination decreases with age. The seed packet label usually indicates essential information about the cultivar, the year in which the seeds were packaged, the germination percentage, and whether the seeds have received any chemical treatment.
If seeds are obtained well ahead of the actual sowing date (or are surplus seeds), store them in a cool, dry place. Laminated foil packages help ensure dry storage. Paper packets are best kept in tightly sealed containers and maintained around 40oF in low humidity. A good storage location would be an airtight jar or a sealed, Zip-Lock-type bag in the refrigerator. Some gardeners save seed from their own gardens, but these may not produce plants similar to the parents; this is especially true of hybrids.
Germination is the resumption of active embryo growth after a dormant period. Three conditions must be satisfied in order for a seed to germinate: The seed must be viable (the embryo must be alive and capable of germination). Internal conditions of the seed must be favorable for germination, that is, any physical, chemical, or physiological barriers to germination must have disappeared or must have been removed by the propagator and finally, the seed must be subjected to appropriate environmental conditions, including water (moisture), proper temperature, oxygen, and for some species, light.
The first step in germination is absorption of water. An adequate, continuous supply of moisture is important to ensure germination. Once germination has begun, a dry period can kill the embryo.
Temperature affects the germination percentage and the rate (speed) of germination. Some seeds will germinate over a wide range of temperatures while others have a narrow range. Many species have minimum, maximum, and optimum temperatures at which they germinate. For example, seeds of tomato have a minimum germination temperature of 50oF, a maximum of 95oF, and an optimum germination temperature of 80oF. When germination temperatures are listed, they are usually optimum temperatures. Generally, 65oF to 75oF is best for most plants.
Light can stimulate or inhibit seed germination of some species. Seeds that require light for germination include: ageratum, begonia, browallia, impatiens, lettuce, and petunia. Other plants germinate best in the dark. These include calendula, centaurea, annual phlox, and verbena. Some plants germinate in either light or dark conditions. Seed catalogs and seed packets often list germination and cultural information for particular plants. When sowing light-requiring seeds, sow them on the medium surface. Fluorescent fixtures suspended 6 to 12 inches above the medium for 16 hours a day can provide supplemental light.
A wide range of media can be used to germinate seeds. With experience, you will learn to determine what works best for you. The germinating medium should be rather fine in texture and of uniform consistency, yet well aerated and loose. It should be free of insects, disease organisms, nematodes, weeds, and weed seeds. It should also be of low fertility and capable of holding moisture, but yet be well drained. Purchase commercial potting media containing fine particle pinebark, sphagnum peat moss, and perlite, or prepare a combination of equal parts (by volume) of these materials. Do not use garden soil to start seedlings; it is not sterile, it is too heavy, and it does not drain well. Commercial mixes have low fertility, so seedlings must be watered with a dilute fertilizer solution soon after germination and emergence. Use 1/4 to 1/2 of the recommended rate.
Plastic cell packs can be purchased or reused if sterilized. When using cell packs, each cell holds a single plant. This method reduces the risk of root injury when transplanting. Peat pellets, peat pots, or expanded foam cubes can also be used for producing seedlings. Resourceful gardeners often use cottage cheese containers, the bottoms of milk cartons or bleach containers. Just make certain that adequate drainage holes are made in the bottoms of the containers and the containers are sterile. The importance of using sterile medium and containers cannot be overemphasized. Before using containers, wash them to remove any debris and then immerse them in a solution of one part chlorine bleach to nine parts water for 5 minutes and allow drying.
Seedlings are often started indoors 4 to 12 weeks before the last spring frost. A common mistake is to sow the seeds too early and then attempt to hold the seedlings under poor environmental conditions (light and temperature). This usually results in tall, weak, spindly plants that do not perform well in the garden. The following provides general guidelines for sowing seeds for transplants. However, it is important to refer to the instructions on the seed packet for more specific information.