The USDA Hardiness Zone 8 designation signifies a region with mild winters, characterized by average minimum temperatures ranging from 10°F to 20°F. This temperate climate allows for a long growing season, supporting both cool- and warm-season crops. March is a transition point, marking when the last threats of deep cold recede and the ground becomes workable. This guide provides advice for maximizing the productivity and color of a Zone 8 garden during this pivotal early spring month.
Understanding the Zone 8 March Climate
March is defined by the average last spring frost date, which typically falls between the middle and end of the month (March 13th to April 7th). Gardeners should watch local weather forecasts for unexpected cold snaps, as the period before this date is safe only for crops that tolerate light freezing temperatures.
A more reliable indicator than air temperature is the soil temperature, which must be conducive to seed germination. Cool-season vegetables require minimum soil temperatures consistently above 40°F to sprout. Using a soil thermometer to check the top two to four inches of the garden bed is more accurate than relying on the calendar. Planting seeds when the soil is too cold results in slow, poor germination and can cause seeds to rot.
Direct Sowing Hardy Edibles Outdoors
The warming March soil is perfect for direct sowing hardy, cool-season vegetables that thrive below 70°F. English peas benefit from an early start and should be planted directly into the soil with a trellis or support structure. Root vegetables, including radishes, carrots, and turnips, must be direct-sown because they do not transplant well and suffer from root deformation.
Leafy greens, such as spinach, kale, and Swiss chard, are highly cold-tolerant and can be planted now for a continuous spring harvest. The seedbed for carrots and radishes should be finely tilled and free of large debris to prevent misshapen roots. Thinning seedlings after they emerge is necessary for all direct-sown crops to ensure adequate space and air circulation. Staggering the planting of quick-maturing crops like radishes and lettuce every two weeks ensures a steady, continuous supply.
Starting Tender Crops Indoors and Transplanting
March is the time to start heat-loving vegetable seeds indoors, as they require a long growing season before being safely moved outside after the last frost. Tomatoes, peppers, and eggplants need eight to ten weeks of indoor growth to reach optimal transplant size. These seeds benefit from heat mats to maintain a consistent soil temperature (75°F to 85°F), which encourages rapid germination.
Seedlings must be placed under strong grow lights immediately after sprouting to prevent them from becoming leggy. This is also the time to transplant cool-season crops started indoors earlier, such as hardy brassicas and onion and leek sets. These plants can be hardened off and moved into their permanent spots. Hardening off is the gradual process of acclimating young plants to outdoor conditions by exposing them to increasing periods of sun, wind, and cooler temperatures over seven to ten days before planting.
Spring Flowers and Ornamental Plants
Gardeners can begin adding color by planting hardy annuals and summer-blooming bulbs in March. Hardy annuals like sweet peas, poppies, and calendula can be direct-sown into the garden beds, as their seeds require the cool, moist soil of early spring to germinate. These plants tolerate light frost and provide the earliest floral displays.
Summer-flowering bulbs and tubers, including dahlias, gladiolus, and cannas, can be planted late in the month once the soil is reliably workable. Although these plants are not frost-tolerant, planting them now allows them to establish a robust root system before summer heat arrives. March is also a good time to divide and transplant fall-blooming perennials before they break dormancy and begin new growth.