The timing of a successful garden in Arkansas depends on understanding the state’s diverse climate, which spans from the cooler Ozark Mountains in the north to the warmer Gulf Coastal Plain in the south. Arkansas’s USDA Plant Hardiness Zones generally range from 7a to 8b, reflecting a significant difference in the length of the growing season. Planting too early or too late can lead to stunted growth or crop failure, so a precise schedule based on local conditions is necessary for maximizing spring and fall harvests.
Pinpointing the Last Frost Date in Arkansas
The most important factor for spring planting is the last expected date of a spring freeze, which determines when it is safe to introduce frost-sensitive plants. Due to Arkansas’s size, this date varies significantly; southern regions may see their last freeze in early March, while the northern highlands might not be safe until late April or early May.
Gardeners should consult historical data from a reliable source, such as the local County Extension office, to find the average last spring freeze date for their location. This average date represents a 50% probability that a freeze will occur afterward. Experienced gardeners often wait an additional two weeks past this date to reach the “safe date,” which has a much lower probability of a killing frost.
A freeze is defined as a temperature drop to 32°F or below, but temperatures in the 33°F to 36°F range can also damage tender plants. Knowing the average date allows a gardener to plan the spring planting schedule by counting forward from that benchmark. Planting based on historical data prevents the mistake of losing young plants to a late cold snap.
Planting Cool-Season Vegetables in Early Spring
Cool-season vegetables thrive in moderate spring temperatures and must be planted early enough to mature before the summer heat arrives. These crops tolerate light frost and require a minimum soil temperature of 40°F to 50°F for germination. The ideal root zone temperature range is between 50°F and 70°F.
Crops like peas, spinach, radishes, lettuce, and carrots can be direct-sown four to six weeks before the last expected frost date. If the last freeze is mid-April, sowing can begin in early to mid-March once the soil is workable. Other cool-season vegetables like broccoli, cabbage, and kale are often started indoors and transplanted outside near the average last frost date.
Planting these vegetables in early spring allows them to complete their growth cycle before high temperatures consistently reach the upper 80s. High heat can cause them to “bolt,” or prematurely flower and set seed. Using a soil thermometer to confirm the 45°F to 50°F range ensures the soil is warm enough for strong root growth and nutrient uptake.
Planting Warm-Season Crops Safely
Warm-season crops, such as tomatoes, peppers, squash, corn, and melons, are sensitive to cold and require warmer conditions. These heat-loving transplants should not be placed in the garden until all danger of frost has passed and the soil temperature has warmed consistently.
These tender crops require a minimum soil temperature of 60°F to 65°F at a depth of four inches for successful planting. Tomatoes specifically require the soil temperature to be closer to 65°F to 70°F. Planting into cold soil, even if the air is warm, can cause severe transplant shock and stunted growth.
Safe planting windows range from mid-April in the warmer Zone 8 areas of South Arkansas to late April or early May in the cooler Zone 7 areas. Waiting until the soil temperature remains consistently warm increases the chance of a bountiful harvest. Using a soil thermometer is a more accurate guide than relying solely on the calendar date.
Planning for a Second Harvest: Fall Gardening
Successful fall gardening focuses on the first expected fall freeze. This requires planting cool-season crops during the summer heat so they can mature before the season ends. The average first freeze date ranges from late October in northern Arkansas to early November in the south.
To determine the correct planting date, count backward from the estimated first fall freeze date using the days to maturity, plus one to two weeks for slower growth as days shorten. Many cool-season vegetables, including kale, collards, spinach, and carrots, can be planted for a fall harvest. Optimal planting times typically fall between mid-July and mid-September.
For instance, collard greens and turnips should be sown between August 1 and September 15. Starting seeds in the heat of August requires keeping the soil moist and cool, often by covering rows until germination. This timing ensures plants reach a harvestable size before the first killing frost.