What to plant in USDA Hardiness Zone 6 depends entirely on the current season, as this region experiences four distinct periods of gardening activity. Zone 6 is defined by its average annual extreme minimum winter temperatures falling between -10°F and 0°F, supporting a wide range of plants. The moderate length of the growing season allows for both early cool-weather crops and a full summer of heat-loving vegetables. Understanding the annual rhythm of frost dates and soil temperature is the foundation for a successful garden.
Key Timing Factors for Zone 6 Gardening
The timing of planting activities in Zone 6 is governed by the average last spring frost and the average first fall frost. The last expected frost date typically falls between April 1st and April 21st, sometimes as late as May 1st. This date signals the transition to the warm-season planting window. The first fall frost is generally anticipated between October 17th and October 31st, marking the end of the warm-season growing period.
Gardeners must monitor soil temperature, which lags behind air temperature. Cool-season crops require soil temperatures of at least 40°F to 50°F for establishment, while warm-season crops need a warmer environment, typically above 60°F. Planting seeds in cold soil can lead to rot or delayed germination.
Cool-season vegetables are frost-tolerant and thrive in mild spring and fall temperatures. They should be planted 4 to 6 weeks before the last frost. Warm-season varieties are sensitive to frost and should only be placed outdoors after all danger of freezing has passed and the soil has warmed.
Spring and Early Summer Planting Guide
The spring planting season begins indoors, often 6 to 8 weeks before the last predicted frost date, to give heat-loving crops a head start. Tomatoes, peppers, and eggplants benefit from being started inside and transplanted later. This early indoor start is necessary because the zone’s growing window is often not long enough for these plants to reach full maturity if directly sown outdoors.
Early Spring (Cool Season Crops)
As soon as the soil is workable, cold-hardy vegetables can be direct-sown, potentially as early as March. These crops handle a light freeze and prefer to mature before summer heat causes them to bolt or become bitter.
Cool-season vegetables like peas, radishes, spinach, and lettuce can be planted 4 to 6 weeks before the last frost. Kale, Swiss chard, and carrots can also be sown early. Broccoli, cabbage, and Brussels sprouts are often started indoors and transplanted outdoors around the last frost date. Planting these frost-tolerant vegetables in succession every two weeks ensures a continuous harvest throughout the spring.
Late Spring/Early Summer (Warm Season Crops)
Planting of all warm-season crops must be delayed until after the last expected frost date, typically in late April or early May, when the soil has warmed. Transplants of tomatoes, peppers, and eggplants are moved out during this period. These plants are susceptible to cold damage and their growth will be stunted if they encounter a late cold snap.
Direct sowing of warm-season seeds like beans, corn, cucumbers, and squash is done after air and soil temperatures consistently remain warm, usually in late May or early June. Basil should also wait until this time for planting outdoors. Selecting varieties with shorter “days to maturity” helps ensure a successful harvest before the autumn frost arrives.
Flowers and Herbs
The spring season is also the time for planting annual flowers and dividing perennial garden favorites. Tender annuals, such as petunias and zinnias, should only be planted after the last frost date, similar to warm-season vegetables, as they cannot survive freezing temperatures. Perennial divisions of hostas and daylilies can be successfully transplanted as soon as the soil is thawed and workable.
Perennial herbs like thyme, oregano, and sage can be planted from transplants as the weather warms. Hardy annual herbs like cilantro and dill can be planted early in the spring for a harvest before they bolt in the summer heat. Basil, which is highly sensitive to cold, should wait until the weather is consistently warm.
Late Summer and Fall Planting Guide
Late summer marks the beginning of the second growing season in Zone 6. This phase utilizes the still-warm soil temperatures of mid-to-late summer to establish new plantings that will mature in the cooler autumn weather. The main consideration is calculating “days to maturity” backward from the average first frost date, ensuring crops ripen before a killing freeze.
Succession Planting/Fall Crops
Mid-to-late summer, typically mid-August to September, is the window for planting a second round of cool-season vegetables. Leafy greens like spinach, kale, and lettuce thrive in the shorter days and cooler temperatures of fall, often developing a sweeter flavor after a light frost. Carrots, beets, radishes, and turnips are also excellent choices for fall harvesting and can be direct-sown during this time.
Brassicas like broccoli and cabbage for a fall harvest should be started indoors in mid-summer and transplanted into the garden in August. The cooler fall air helps these plants form tight, flavorful heads. Using lightweight row covers is an effective technique to protect these crops and extend the harvest window further into the colder season.
Overwintering Crops
Late fall is the optimal time to plant crops that require cold dormancy, known as vernalization, to produce a harvest the following year. Garlic is the most common overwintering crop, planted in October or early November to establish roots before the ground freezes solid. Certain perennial onions can also be planted at this time for an early spring harvest.
Spring Preparation
The planting of spring-blooming bulbs is a significant fall activity. Tulips, daffodils, crocus, and hyacinths require a period of cold to flower properly and should be planted during October and early November. This late-season planting ensures that the bulbs root before the hardest freezes, providing the first color of the next spring.