A cole crop set out too early can bolt or "button"
A cole crop set out too early can bolt or "button". A long spell of cold on a young plant vernalizes it, and instead of a full head it runs to a premature flower stalk or forms a small, misshapen head.
Promising A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
Cabbage, broccoli, cauliflower and their kin are biennials, so cold is their signal that a winter has passed and it is time to flower. A young plant that accumulates enough cold (a stretch of weather in the 40s F) is vernalized and switches from building leaves and a head to running up a flower stalk and setting seed. Set out before the weather has settled, a small transplant crosses that cold threshold before it has grown the leafy bulk a head needs, so it buttons (a tiny premature head) or bolts (runs to seed) and never heads properly.
What to do about it
Aim for cool-but-moderate weather (roughly the 50s and 60s F) through the plant's first weeks, and don't rush an early set-out; a stout transplant with several true leaves shrugs off a cold snap that would vernalize a tiny one, and a row cover holds the cold off if a spell threatens. This is the opposite failure from over-tender growth. Harden the plant, but do not set it out into a cold that will check it.
How much it matters: No threshold or figure is given. The sources give a range (settled weather in the 50s-60s F for the first weeks), with no single number. The risk is highest for a small transplant set out into a cold spell and lowest for a well-grown one set out into settled weather, so the rule only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
Bolting refers to premature flowering. It occurs at any point after a plant has shifted into its reproductive stage
Biennial vegetable crops complete their life cycle in 2 years. But many will produce flower stalks in response to cool or hot temperatures and long days
Plants it applies to
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Wording made clearer
- A person read the sources and confirmed it
- Added to the rules
Cite this page
Milpa Gardens. "A cole crop set out too early can bolt or "button". A long spell of cold on a young plant vernalizes it, and instead of a full head it runs to a premature flower stalk or forms a small, misshapen head." Evidence grade: Promising. https://milpa.garden/rules/cole-crop-set-out-too-early-can/
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