Gardening in Alabama: zones, frost dates and when to plant

North, central and south Alabama

Between Huntsville and Mobile, the difference across Alabama shows up mostly in how long winter hangs on. According to the state climatologist’s office at UAH, freezes end earliest along the Gulf Coast, a few weeks later in central Alabama, and latest in the north, where cooler air and higher ground keep frost around well into spring. The NOAA state climate summary puts it in plain numbers: average winter nighttime lows run near 30°F in the north and above 45°F on the coast, and Huntsville sees more than twice as many freezing nights a year as Mobile.

Alabama Extension builds its planting chart around central Alabama and asks you to shift it. For spring crops, south Alabama plants about 10 days earlier and north Alabama about 10 days later; for fall crops the shift reverses. The separate fall gardening guide suggests a bigger adjustment for fall, about two weeks either way, so treat those offsets as a range. Check the frost dates for your city above, then move with the weather rather than the calendar.

Heat, rain and a two-season garden

Alabama’s long-term average is about 55 inches of rain a year, but it is not evenly spread. The UAH climate office lists December and January as the wettest months and October and May as the driest, so a dry spell can arrive right when fall seedlings need water. NOAA’s summary notes that summer days above 95°F are common.

Summer heat is why Alabama gardens split into a spring and a fall season. The Alabama Vegetable Gardener (ANR-0479), the state Extension handbook, notes that cabbage cannot take the state’s summer heat and belongs in early spring or fall, and that lettuce bolts and turns bitter in high summer temperatures unless you choose a heat-tolerant variety. Warm-season crops follow the opposite rule: okra should wait until three to four weeks after the last frost, and southern peas and watermelons go in only after frost danger has passed.

Fall is a productive season here. The fall guide (ANR-1422) puts most crops in from July through early September, including broccoli, collards, turnips, spinach and onions. Direct-seeded fall crops depend on steady moisture after germination, and the guide suggests an overhead sprinkler to get seed up in late-summer heat. The handbook adds that tomatoes can keep bearing until frost, so gardeners in south and central Alabama can often pick into November and sometimes December.

Acid soil and drainage

The handbook is blunt that low pH causes more garden trouble in Alabama than any other soil factor. Heavy rain leaches basic minerals over time, and manure, compost and fertilizer speed the process. In very acid soil, aluminum and manganese can reach toxic levels and calcium and magnesium run short. Most Alabama garden soils need lime every 3 to 5 years, with a target pH of about 6.0 to 6.5 for most vegetables. Irish potatoes are the exception and tolerate a lower pH, which also suppresses scab.

Phosphorus is the other surprise. Auburn soil-test records show that more than 40 percent of Alabama garden soils carry high or excessive phosphorus, usually from years of complete fertilizers such as 13-13-13 and heavy manure or compost. Phosphorus does not leach, so it accumulates.

Clay that stays wet is common. Extension suggests working in organic matter, forming raised beds in fall so they are ready and warm faster in spring, and building soil up on top of poorly drained clay instead of digging deep holes that hold water like a bathtub.

Nematodes and disease

Root-knot nematode is the most widespread nematode in the state and attacks nearly every vegetable, with sweet corn the possible exception. Stunted, yellowing or wilting plants on a site with good fertility and pH are a warning sign. Extension recommends keeping tomatoes, peppers and potatoes off the same spot for at least two years. Choose tomatoes labeled V, F and N for resistance to Verticillium wilt, Fusarium wilt and root-knot nematode. In humid weather, water early in the day so leaves dry before night, and soak the garden thoroughly once a week in dry spells rather than sprinkling daily.

The handbook’s tomato list includes Celebrity, Bella Rosa (heat-tolerant, with tomato spotted wilt resistance), Amelia VR and Red Defender. For fall, the ANR-1422 guide names collards such as Vates and Blue Max and broccoli such as Packman and Green Duke.

Start with a soil test

Extension calls a soil test the only way to set lime rates and the best guide to fertilizer. Your county Extension office can tell you how to collect and submit a sample. Test at least every two years, and mix lime into the soil a month or two before planting so it has time to react.