To start plant from seeds, the easiest and least time consuming way is to plant them directly in the garden. But if you want to get a head start on the growing season, you can start seeds indoors or in a greenhouse and transplant the seedlings into the garden when the weather is favorable.
There are other advantages to starting seeds indoors: you have more control over light, temperature and moisture requirements. You can use sterile potting mixes to help prevent diseases. You can also protect delicate seedlings from insects, birds, weeds and other pests. Because of these factors, the germination rate of seeds grown indoors is usually higher.
Although the germination rate is usually lower with seeds planted directly in the garden, and losses to pests and diseases is higher, the plants that survive outdoor sowing are usually better adapted. Transplanting often causes shock, and many plants have to be gradually adjusted to outdoor conditions, before they are planted. This also is best for plants that do not transplant well during the seedling stage and those that are to be planted in quantity over a large area, such as ground covers. Raising and transplanting hundreds of seedlings can be a tedious chore.
Buy the highest quality seeds available. Most national seed rack and mail order brands are uniformly high quality. Beware: Seeds that have been discounted because they are outdated are no bargain. The newer or fresher the seed, the better. Seed companies test germination and some print the test date and germination percentage on the package. If you buy and sow the seed within six months of the tested date, you can assume the germination percentage is not reduced. Seed packages usually show the year they are packaged for or give an expiration date.
If you have seeds left over from last year, you may wonder if they are still viable. Some seeds, such as sweet peas, remain viable for several years while others are only good for a year or less. If you are in doubt, you can always test seed viability. Spread seeds over a moist paper towel and wait for germination. Keep the seeds warm and maintain humidity by covering with plastic wrap or another suitable material. Calculate the germination percentage by dividing the number of seeds that germinated by the number tested.