The rutabaga (Brassica napobrassica) is a root vegetable resulting from a cross between a turnip and a wild cabbage. It is often confused with the turnip, but the rutabaga is generally larger, has a sweeter, more yellow-fleshed root, and thrives in cooler weather. Gardening in USDA Hardiness Zone 9 presents a unique challenge for this cool-season crop, given the zone’s mild winters and long, intensely hot summers. Successfully growing rutabaga relies entirely on timing the planting so the root development and maturation occur during the cool period for a successful harvest.
Rutabaga’s Ideal Growing Conditions
Rutabaga requires a cool climate for proper root formation and flavor development. The plant grows best when air temperatures remain consistently between 50°F and 65°F during maturation. Optimal soil temperatures for germination range from 40°F to 60°F. This preference explains why it is almost exclusively grown as a fall and winter crop in Zone 9.
The cool weather is responsible for the vegetable’s quality, as the plant converts starches in the root into sugars. A light frost, common in Zone 9 during winter, further enhances this conversion, leading to the characteristic sweet flavor. Conversely, sustained temperatures above 80°F during root development will cause the plant to stop forming a quality root, leading to bolting, bitterness, or a woody, fibrous texture.
Zone 9 Specific Planting Schedule
Given the intense summer heat in Zone 9, rutabaga must be grown as a fall and winter crop, completely avoiding the spring and early summer heat. The goal is to time the direct sowing so that the 90 to 100-day maturation period concludes during the mild winter months. This ensures the developing roots benefit from the necessary drop in temperature.
The ideal planting window begins in late August and extends through October. Sowing during this period allows young plants to establish themselves as the intense summer heat subsides, with cooler weather driving the root’s growth. Succession planting is highly recommended: sow a new, small batch of seeds every two to three weeks until late October to extend the harvest period.
Spring planting is not practical in this zone because the long maturity time means the root would develop during the rapidly heating conditions of late spring and early summer. The quick rise in temperature forces the plant to bolt, or flower prematurely, before the root can fully form, resulting in a small, low-quality, and inedible harvest.
Essential Preparation and Sowing Methods
Rutabaga thrives in deep, loose, and well-draining soil, which is necessary for the root to expand uniformly without obstruction. The soil should be fertile and enriched with organic matter, maintaining a slightly acidic to neutral pH between 6.0 and 6.8.
Before planting, the soil should be worked to a depth of at least eight inches, removing any rocks or clumps that could cause the developing roots to fork or become misshapen. Seeds should be directly sown into the prepared bed at a shallow depth of about one-half inch. Consistent moisture is required for successful germination within four to seven days.
Initial spacing can be close, approximately two to four inches apart. Once seedlings develop their first true leaves, thinning must begin. Thinning is necessary for producing large, high-quality rutabagas; remaining plants should be spaced six to eight inches apart. Crowding results in small, underdeveloped roots as they compete for resources, and maintaining consistent soil moisture throughout the growth cycle is also important, as irregular watering can cause the roots to split or become bitter.
Harvesting and Storage
Rutabaga roots are typically ready for harvest approximately 90 to 100 days after planting. They are mature when they reach a diameter of three to five inches, appearing slightly above the soil line. Roots should be carefully dug up using a garden fork to loosen the soil, preventing damage to the skin, which prolongs storage life.
In Zone 9, the roots can often be left in the ground until needed, provided a hard freeze is not anticipated. This acts as natural storage and allows the roots to continue sweetening after exposure to cold temperatures. For long-term storage, trim the green tops to within an inch of the root crown, and place the roots in a cool, dark location, such as a refrigerator or root cellar, for several months.