January is prime seed-starting time

January is a good time to start seeds for cold- tolerant, early spring annuals that need a long lead time before being planted in the garden. Each seed packet has directions, so you’ll know which seeds require bottom heat, light, or darkness to germinate. You may need to do some research to find the specific requirements. Some seeds need a short period of chilling, soaking in water or being nicked before being sown. Cool-season annuals ( like larkspur, snapdragon, English daisy, ranunculus, pansy, annual poppy, forget-me-not, and edging lobelia) can be planted outside in the garden by the second week in April after the young plants are hardened off. Check your calendar, because in a typical season, it may be best to start seeds 14 weeks ahead to have blooming plants ready for outside planting.

Sow seeds in fiber pots or trays, using a pre-moistened, soilless, or seed-starting mix. Sow large seeds in slightly indented rows and cover them lightly with a thin layer of the mix. Finer seeds may be spread directly on top of soil. Some types of seeds need a glass or plastic cover for extra humidity. Water seeds from the bottom or use a fine mister to keep the soil moist. Most seeds require a warm, bright location out of direct sun to germinate. Air out covered seeds daily, especially in bright conditions. To grow these early spring annuals to a big enough size for a good display in the garden, you’ll need good light. The spring season in the Chicago area is short and there is not much time for these plants to develop and flower outside. Many start to decline once the weather starts getting hot.

When you see germination, gradually increase light levels. Most seedlings need 14 to 16 hours of direct light to manufacture enough food to produce healthy stems and leaves. The legginess that can happen when seedlings are grown on a windowsill shows that the plants are not getting enough light intensity, or enough hours of light. Use a full- spectrum fluorescent bulb placed no more than 3 inches away from the foliage. When two sets of true leaves develop, transplant small seedlings to a larger fiber pot filled with a slightly coarser "growing-on" mix and begin fertilizing with quarter-strength 10-10-10 solution. As the plants grow larger, switch to a half-strength solution once a week.

A great way to up your seed-starting game: come to the Garden’s Super Seed Saturday on Saturday, Jan. 20.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.