Cabbage is a cool-weather crop that thrives in temperatures between 60 and 65 degrees Fahrenheit. In Oklahoma’s variable climate, timing is crucial; planting at the wrong time can expose young plants to temperature extremes, causing them to fail to form heads or bolt prematurely. Success depends on scheduling planting so the crop matures before the intense heat of summer or a hard winter freeze. Oklahoma gardens have two distinct planting windows for cabbage.
Establishing the Optimal Planting Windows
Oklahoma’s climate permits two distinct growing seasons for cabbage: a spring crop and a fall crop, each timed around the state’s average frost dates. For the spring crop, the goal is to transplant seedlings into the garden approximately four to six weeks before the average last spring frost. The last spring frost date is typically around April 10th in Oklahoma City and April 5th in Tulsa, though this varies across the state. This means seedlings should ideally be transplanted outdoors between late February and mid-March, allowing the heads to develop during the cooler days of spring.
The timing for the fall crop revolves around the first expected hard freeze, which signals the end of the growing season. Across much of the state, the average first frost occurs between early and mid-November. To calculate the planting date, count backward from this first frost date by the variety’s “days to maturity,” plus an additional two to three weeks for establishment. This calculation usually dictates that seeds must be started indoors in mid-July and transplanted into the garden by mid-to-late August or early September. Planting the fall crop is more challenging because the seedlings must be established during the summer’s highest temperatures, but the resulting harvest benefits from the cool, bright days of autumn.
Preparation Before Planting
Successful cabbage production requires proper site selection and soil preparation. Cabbage needs a location that receives full sun (at least six to eight hours of direct sunlight per day), though some afternoon shade can benefit fall crops started in the summer heat. Since cabbage is a heavy feeder with a relatively shallow root system, the soil is a critical factor.
The planting site needs fertile, well-drained soil rich in organic matter to support the plant’s rapid growth. Prior to planting, amend the soil with compost or well-rotted manure to boost organic content and improve water retention. Cabbage thrives in a slightly acidic to neutral pH range (6.0 to 7.0); maintaining this range is important to prevent the common disease known as clubroot. If the soil pH is too low, agricultural lime can be incorporated several weeks before planting to adjust the level.
Gardeners must decide whether to sow seeds indoors or purchase transplants, with seeds allowing for more variety selection. Start seeds indoors approximately six to eight weeks before the intended outdoor transplant date. This ensures seedlings develop five to six true leaves and a sturdy stem, preparing them for the garden environment.
Initial Care and Transitioning Outdoors
The transition from a protected indoor environment to the unpredictable outdoors is a physically taxing process for the young plants. To prevent transplant shock, seedlings must undergo a process called “hardening off,” which slowly acclimates them to sun, wind, and temperature fluctuations. This acclimation should begin seven to fourteen days before the final transplanting date, gradually exposing the plants to outdoor conditions for increasingly longer periods each day. On the first few days, seedlings should only be placed outside in a shaded, sheltered spot for a couple of hours, and they must be brought back inside if temperatures are expected to drop below 45 degrees Fahrenheit.
Once transplanted, immediate care focuses on establishment and protection from environmental stress. At the time of planting, a liquid starter fertilizer applied directly to the root zone encourages rapid root growth. The newly set plants need consistent moisture, especially during the first few weeks, requiring about one inch of water per week through rain or irrigation.
A mulch layer applied around the base of the plants will help maintain soil moisture and temperature, which is especially beneficial in Oklahoma’s fluctuating spring and fall weather. Inspecting for common pests like cutworms immediately after transplanting is also a proactive measure, as damage to the young stem can quickly destroy the plant.