Bolting

Disorderalso: Going to seed, Running to seed

Bolting is when a leafy or cool-season vegetable suddenly sends up a flower stalk and goes to seed, turning bitter and tough in the process. It is a natural response to heat and lengthening days, not a disease, and it commonly ends the harvest of lettuce, spinach, cilantro, and other cool-weather crops as summer arrives.

🔎 How to spot it

Look for a plant that abruptly grows taller and sends up a central flower stalk, with the leaves becoming smaller, narrower, and often more bitter. In lettuce and spinach the head or rosette stretches upward and turns leggy; in cilantro, basil, and brassicas, flower buds and stalks appear. Once the stalk forms, the edible leaves quickly lose quality.

🥀 Damage it causes

Bolting effectively ends the useful harvest: leaves of bolted lettuce, spinach, and herbs turn bitter and tough, roots and bulbs of bolted onions and beets become woody, and the plant pours its energy into seed rather than the part you eat. The crop is not poisonous, just unpalatable, though you can save seed from it.

🔬 What causes it

Bolting is triggered by the plant sensing that conditions favor reproduction, mainly heat and long summer days, and sometimes a cold spell followed by warmth or transplant stress. Cool-season crops like lettuce, spinach, cilantro, and radish bolt as temperatures climb and days lengthen, and drought and root disturbance can hurry it along.

🛡️ Prevent it

Plant cool-season crops early in spring or for a fall harvest, so they mature in cool, shortening days rather than into summer heat. Choose slow-bolt or bolt-resistant varieties. Keep plants evenly watered and unstressed, use shade cloth and mulch to keep roots cool in warm spells, and harvest promptly while the leaves are still tender.

🧯 If it is already here

Bolting cannot be reversed once the flower stalk forms. Harvest what you can right away before it turns too bitter; pinching out flower stalks on herbs buys a little time but not much. The practical response is to pull the bolted plant and resow a fresh, heat-tolerant or fall crop, or let a plant or two flower for pollinators and seed.

💡 Good to know

Bolting is a calendar and weather problem, not a pest, so the fix is timing rather than treatment: grow cool-season crops in the cool ends of the season. Letting cilantro or a brassica bolt is not all bad, since the flowers feed pollinators and you can collect seed, such as coriander from cilantro.

🌱 Plants it affects

130 plants in the library can be affected by this problem

African Blue Basil

Arugula 🥕Atomic Red Carrot 🥬Bibb Lettuce 🥬Black Seeded Simpson Lettuce 🥕Black Spanish Radish

Bloomsdale Spinach

Bok Choy 🥕Bolero Carrot

Calabrese Broccoli 🥬Champion Collards

Detroit Dark Red Beet

Dill

Dragon Carrot

Dwarf Blue Curled Vates Kale 🥬Dwarf Siberian Kale 🌸Easter Egg Radish

Egyptian Walking Onion

Elephant Garlic

Endive

Florence Fennel 🥕French Breakfast Radish

Frisée

Garlic Chives

Genovese Basil 🧄German Extra Hardy Garlic

Imperator Carrot 🧄Inchelium Red Garlic

Italian Flat-Leaf Parsley

Italian Large Leaf Basil

January King Cabbage 🧄Killarney Red Garlic

Lettuce-Leaf Basil 🥬Little Gem Lettuce 🥬Lollo Rossa Lettuce

Mâche

Malabar Spinach

Mizuna 🥕Mokum Carrot

Music Hardneck Garlic

Mustard Greens

Nantes Carrot

Napa Cabbage

New Zealand Spinach 🥬Oakleaf Lettuce

Orach 🥕Paris Market Carrot

Pearl Onion

Purple Basil 🥦Purple Cape Cauliflower

Purple Sprouting Broccoli

Purple Top Turnip

Purslane

Radicchio 🥕Rainbow Carrot Mix

Rainbow Chard

Red Cabbage

Red Leaf Lettuce 🧅Red Onion

Red Russian Kale

Redbor Kale

Romaine Lettuce

Romanesco Cauliflower

Rutabaga

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.