Bolting
Plant disorder
Description
Bolting is the premature switch from leafy or root growth to producing a flower stalk and seeds. It is a normal part of a plant’s life cycle, but it becomes a garden problem when it happens before a crop is ready to harvest. Lettuce, spinach, cilantro, radishes and other cool-season crops are particularly prone to it. Depending on the crop, long days, rising temperatures, cold exposure earlier in growth, or stresses such as drought can trigger the change. A bolting plant often sends up a rapidly lengthening central stem with flower buds at its tip. Leaves may become smaller, tougher or bitter; edible roots may turn fibrous or woody. Once flowering begins, the plant puts more energy into seed production and less into the leaves or roots being grown for food. Bolting is a growth response, not an infection, and it cannot spread from plant to plant.
Symptoms
- Flowering too early (bolting)
How to Identify
Look for a central stalk that grows taller than the surrounding leaves and develops buds or flowers earlier than expected for the crop. Check the rest of the plant: lettuce or spinach leaves may taste bitter, while a harvested radish may be woody. Normal flowering looks similar, so timing and intended harvest matter—a seed crop flowering on schedule is not a problem. Bolting differs from drought-related wilting or nutrient-related stunting because it produces a distinct reproductive stalk. In biennial vegetables, flowering in the first growing season rather than the second may follow exposure to cold when the plants were young.
Prevention
Choose bolt-resistant varieties when available, and sow each crop in a season suited to its temperature needs. Plant cool-season greens early enough to harvest before sustained heat, or grow them in the cooler part of autumn. Make small, successive sowings so one hot spell does not ruin the entire harvest. In warm weather, afternoon shade can help keep leafy crops cooler, though it cannot change day length. Water consistently, use mulch to moderate soil temperature and moisture, and give plants enough space to avoid competition. Avoid leaving seedlings root-bound or disturbing their roots unnecessarily when transplanting. For crops whose flowering is triggered by cold exposure, follow local sowing guidance so young plants are not exposed to prolonged cold before they establish.
Treatment
First, harvest usable leaves or roots promptly. Taste a leaf before picking a large quantity: some remain edible, while others have become too bitter or tough. For herbs such as basil, pinching off flower buds and harvesting stem tips may encourage more leafy growth if the plant has only just begun to flower. This is usually a delay, not a reversal. For crops such as lettuce and spinach, cutting off the flower stalk rarely restores tender leaf production. Remove spent plants and sow a new crop if growing conditions are suitable, or wait for cooler weather. Alternatively, leave healthy bolting plants in place to provide flowers for pollinators or to collect seed, provided you are comfortable with possible self-seeding. Pesticides and fungicides do not treat bolting because it is not caused by a pest or disease.
Plants Affected
Arugula, Beet, Bok Choy, Broccolini, Carrot, Celeriac, Celery, Chervil, Chinese Broccoli, Chinese Cabbage, Cilantro, Coriander, Daikon, Dill, Endive, Fennel, Kohlrabi, Komatsuna, Leek, Lettuce, Mizuna, Mustard Greens, Napa Cabbage, Onion, Parsley, Parsley Root, Radicchio, Radish, Rapini, Salsify, Shallot, Sorrel, Spinach, Swiss Chard, Tatsoi
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