Cabbage is a cool-season vegetable that requires precise timing to thrive. The goal is to ensure the plant matures during the mild temperatures of spring or fall, avoiding the stress of summer’s intensity. Timing your planting schedule depends on understanding your local frost dates within Zone 7b.
Defining the Zone 7b Climate
USDA Hardiness Zone 7b is defined by its average annual minimum winter temperature, which falls between 5°F and 10°F. The average last spring frost date generally falls between mid-March and early April, marking the point after which the risk of a hard freeze significantly decreases. Conversely, the average first fall frost date typically occurs between late October and mid-November, signaling the close of the warm growing period.
Timing the Spring Cabbage Crop
The spring planting window is designed to allow the cabbage head to form before temperatures consistently climb above 75°F to 80°F, which can cause the plant to bolt or the heads to split. Seeds should be sown indoors approximately six to eight weeks before the last expected spring frost date. This indoor start, usually falling between mid-February and early March, develops robust seedlings ready for the garden.
The young cabbage plants need a process called “hardening off.” The ideal time to transplant these seedlings is two to four weeks before the average last frost date, typically placing the event in mid-to-late March. This early timing is possible because cabbage is a hardy crop, capable of withstanding light frosts and temperatures as low as 20°F. Planting this early ensures the crop reaches maturity during the peak of the mild spring weather, resulting in firm, sweet heads.
Timing the Fall Cabbage Crop
Planting a fall crop requires counting backward from the first expected frost date to allow enough time for the heads to mature before a deep freeze. Cabbage varieties require anywhere from 60 to 90 days to reach full size after transplanting. Therefore, the planting date should be scheduled for approximately 10 to 12 weeks prior to the average first fall frost, placing the target transplant window in late July to mid-August.
The primary challenge for the fall crop is the intense summer heat during the establishment phase, as young seedlings struggle when temperatures exceed 80°F. Direct seeding during this time is difficult due to the warm soil, so starting seeds indoors or buying transplants is highly recommended. If direct seeding is the only option, select a partially shaded spot and maintain consistent moisture to mitigate heat stress. The benefit of a fall harvest is that the mild frosts that occur just before harvest can actually convert starches in the leaves to sugars, which naturally sweetens the cabbage.