Though a number of seed are easily started outdoors where they are to grow, almost all seed can be reliably started indoors. There are two main reasons to start your seed indoors:

1. Some seed types are picky about germinating and require pretty specific conditions to do well, especially if they are tiny seeds. Begonia, Petunia, Pansy, Salvia and Vinca are almost always started indoors before planting out.

2. Many flowers and vegetables require a long growing season before flowering or fruiting and starting them indoors will give them a head start. Tomato, Pepper, Celery, Delphinium, Geranium and Hollyhock are examples of this category.

The listings of individual flowers and vegetables includes information about whether a particular type of seed will start best when sown directly in the garden, or whether it prefers to be started earlier indoors. There is also a list of varieties that resist transplanting.