Learning when to start seeds early indoors and which seeds give the best results is, like all gardening endeavors, a learning process. The goal is to cultivate the healthiest, hardiest seedlings to plant out at the time most advantageous for your growing environment. Along the way, you'll save money and discover more choices for vegetables, flowers and herbs you'll want to try.
Learning your plant hardiness zone and frost-free date is the first step and key to figuring out when to launch this fun and rewarding garden project.
Your Zone and Frost-Free Date
The U.S. Department of Agriculture (USDA) publishes plant hardiness zone maps based on minimum winter temperatures. The website includes interactive features that allow you to find specifics about average weather conditions for your area. The National Gardening Association provides frost-free dates by zone, according to zip code. Local garden centers and cooperative extension offices can also give you this information.
Keep in mind that information is based on averages and not set in stone. Microclimates exist within zones that may require you to make small adjustments. If your garden is located in a low-lying area, it could be more susceptible to late or early frost. Topography (the lay of the land) and large bodies of water create weather conditions and events different from other areas in your zone. Use the average as a starting point, and add or subtract a day here or there, depending on what gives you the best results.
Read Seed Packets
Most seed packages offer a wealth of information. They can tell you if the seed is best started indoors or planted directly in the ground either before or after the last frost date in your zone. Many seed packets include a map of regional growing zones, with a suggested range of planting dates for the enclosed seed. You'll find days to germination and harvest, planting depth, spacing, and care and growing tips. A general rule of thumb is to count back from your frost-free date to determine when to start seeds indoors. The following table gives an estimate for listed crops.
|Recommended No. of Weeks to Start Seeds, Prior to Frost Free Date|
|Vegetable||# Weeks||Flowers||# Weeks||Herbs||# Weeks|
|Brussels Sprouts||4-6||Batchelor Button||4-6||Chamomile||8-12|
Plants to Start Indoors From Seed
Some plants fare better when started early indoors from seed. Others don't tolerate being transplanted, and some germinate so quickly and reliably, it's inefficient to start them indoors. Knowing which is which helps you plan and manage a productive garden, according to your personal schedule and green thumb capabilities.
Fruits and Vegetables
Vegetables that require a long growing season are good choices to start indoors. If your season for cool weather crops is short, consider starting cole crops and leafy greens early. Vining fruits like melons are sweeter when they get plenty of sun, and winter squashes develop more sugars when temperatures fall. These crops can be timed to mature when growing conditions are ideal. Some of the easiest to grow with the best results include:
- All tomato varieties
- Bell peppers
- Chili peppers
- Winter squash
- Cole crops-cabbage, kale, cauliflower, Brussels sprouts
- Leafy greens-lettuces, Swiss chard, spinach
Annual and Perennial Flowers
Starting ornamentals indoors instead of direct sowing usually results in earlier flowers with a longer bloom time. There are exceptions, like Zinnias, which sprout reliably by scattering seed after the last frost. Perennials tend to have more specific growing requirements, like cold stratification or scarification, which makes the annuals listed here a better choice to grow from seed.
- Bachelor button
- Sweet Pea
Plenty of herbs, both annual and perennial, give good results when started indoors. These include the most popular kitchen (culinary) herbs. A few perennial herbs, like French Tarragon, are difficult to get started, so a purchased seedling is well worth the expense. Here are seeds you might like to start early for your herb garden.
- basil varieties
- mint varieties
Plants to Direct Sow
Root crops and more traditional row crops like peas, beans and corn, are easily grown by sowing seed directly in the garden. Exceptions include onions, which can be started from sets, and sweet potatoes, which can be set out as slips (young plants) to give growers a head start. Other crops, including cucumbers and summer squashes, germinate so quickly and reliably there is no real benefit to starting them early indoors.