Kohlrabi is a unique member of the Brassica family, sharing lineage with cabbage, broccoli, and kale. The edible part is the swollen, globe-like stem that grows just above the soil line. It is prized for its mild, slightly sweet flavor and refreshing, crunchy texture. Achieving the best flavor depends entirely on harvesting the stem at the precise moment of peak tenderness.
Identifying Optimal Harvest Size and Timing
The most reliable indicator for harvesting kohlrabi is the diameter of the swollen stem, which should be between 2 and 4 inches for most varieties. Harvesting within this size range ensures the stem is succulent and sweet, avoiding a tough or woody texture. Allowing the stem to grow larger than 4 inches results in a fibrous interior and a less palatable eating experience.
The time from planting to harvest typically ranges from 50 to 70 days. Kohlrabi is a cool-season crop that thrives in temperatures between 59 and 68 degrees Fahrenheit during stem formation. For spring crops, harvesting must occur before hot summer weather causes the stem to become tough. Fall crops benefit from cooler temperatures, often enhancing the sweetness of the stem.
Visual and Textural Indicators of Readiness
While size is a good guide, the physical condition of the plant offers confirmation of its readiness. A healthy kohlrabi stem ready for harvest should feel firm and solid to the touch. If the stem feels spongy, hollow, or has a soft spot, it is likely past its prime, indicating the onset of woodiness.
The skin of the swollen stem should appear smooth and unblemished; a tough or cracked exterior suggests the plant was left in the ground too long. The surrounding leaves should be a vibrant, healthy green. Yellowing or wilting leaves indicate the plant is redirecting energy away from the stem, suggesting reduced quality.
Proper Harvesting Techniques
Harvesting the kohlrabi stem requires a clean cut to avoid damaging the edible portion. Use a sharp knife or pruning shears to cut the swollen stem cleanly at its base, just below where it connects to the primary root. The root structure can be left in the ground, or the entire plant can be pulled up and the root trimmed off.
After separating the stem, the large, leafy stalks extending from the bulb should be trimmed immediately. These leaves are edible, but they draw moisture from the central stem, which can lead to wilting and toughening if left attached. When harvesting the leaves during the growing season, only snip the outer stalks and never remove more than a third of the foliage.
Post-Harvest Handling and Storage
The first step in post-harvest handling is to remove all the leaves and the root, known as topping the kohlrabi. This trimming is essential because the leaves actively transpire, pulling moisture out of the stem and causing it to shrivel quickly. Once topped, gently wash the stems to remove any soil residue before storage.
Kohlrabi stems store best in cold, high-humidity conditions, typically at 32 degrees Fahrenheit with at least 95 percent relative humidity. Placing the stems in a perforated plastic bag within the refrigerator’s crisper drawer helps maintain moisture without trapping excessive condensation. Stored this way, the stems can maintain quality for two to three months. The edible greens should be stored separately and consumed within a few days, as their shelf life is much shorter.