Brussels sprouts are a cool-season crop, but growing them successfully in Oklahoma is challenging due to the state’s temperature extremes. The plants require a long, cool period to form tight, flavorful sprouts. This is difficult to achieve given the intense summer heat and unpredictable spring temperatures. Precise planting timing is the most important factor for a successful harvest in this climate.
Optimal Planting Schedule for Oklahoma
The most reliable method for growing Brussels sprouts in Oklahoma is aiming for a fall harvest, allowing the sprouts to mature during cooling temperatures. For a fall crop, start seeds indoors around mid-summer, specifically between early to mid-July. This early indoor start ensures the plants reach a substantial size before the harvest window.
Seedlings are ready for transplanting when they are 4 to 6 weeks old, typically between late August and early September. This timing ensures the plants are established and actively growing as summer heat subsides. The goal is for the plants to spend their final 90 to 110 days maturing in the cool weather of late fall and early winter. Harvest often extends into December.
A spring crop is possible, but it carries a greater risk of failure due to the rapid onset of high heat. For spring planting, start seeds indoors 6 to 8 weeks before the average last spring frost date, usually in late February or early March. Transplant seedlings outdoors in late March or early April, as soon as the soil is workable. Plants must mature quickly before sustained temperatures above 80°F cause the sprouts to become loose and bitter.
Choosing a Location and Preparing Soil
Brussels sprouts thrive in a location receiving a minimum of six to eight hours of direct sunlight daily. A full-sun site provides the energy needed for the plant to develop its tall stalk and numerous sprouts. Proper soil is equally important, as these plants are heavy feeders requiring a nutrient-rich environment for their long growing season.
The soil must be well-drained to prevent root rot. Prepare the soil before planting with a generous amount of organic matter, such as aged compost or manure. Amending the soil improves fertility and helps maintain consistent moisture levels. Brussels sprouts prefer a slightly acidic to neutral soil pH, ideally around 6.8, which helps discourage diseases like clubroot.
When transplanting, give each plant plenty of room to grow, as they can reach up to three feet tall. Space individual plants 18 to 24 inches apart within the row. If planting multiple rows, allow 30 to 36 inches between them. This spacing ensures adequate air circulation and access for maintenance and harvesting.
Essential Care and Pest Management
Consistent water delivery is necessary for developing firm, sweet sprouts, especially during hot Oklahoma summers. Plants require about 1 to 1.5 inches of water per week, often needing supplemental watering during dry spells or heat spikes. Inconsistent moisture leads to weak sprout formation and stresses the plants, making them susceptible to pests.
Brussels sprouts are heavy feeders, particularly requiring nitrogen to fuel substantial leaf and stalk growth. About two to four weeks after transplanting, side-dress the plants with a nitrogen-rich fertilizer. Repeat this application every three to four weeks as the plants grow taller and begin forming sprouts.
Pest management is a continuous effort, as the Brassica family is a target for several common Oklahoma insects. Imported cabbage worms and cabbage loopers are a primary concern. Their larvae chew holes in the foliage and can burrow into developing sprouts. Simple, non-chemical controls include hand-picking visible caterpillars from the leaves.
Aphids are another persistent pest that colonize the undersides of leaves and growing tips. Applying a strong jet of water can dislodge aphids, or insecticidal soap or neem oil can manage heavy infestations. Floating row covers can be used early in the season to physically block flying pests, like white cabbage moths, from laying eggs on the leaves.
Knowing When to Harvest
Harvesting should begin once the sprouts are firm, densely packed, and 1 to 1.5 inches in diameter. The sprouts mature sequentially, starting from the bottom of the stalk and progressing upward toward the growing tip. Harvest by snapping or twisting the lowest, firmest sprouts off the stalk by hand.
To encourage remaining sprouts to size up quickly, remove the large, yellowing lower leaves as you harvest the mature sprouts beneath them. For a simultaneous harvest, “topping” involves pinching out the plant’s growing tip (terminal bud). Do this about four to five weeks before the first expected hard freeze. This redirects the plant’s energy into maturing all the remaining side sprouts at once.