Potato tubers that catch light while growing
Potato tubers that catch light while growing (wherever soil settles or washes away and shallow tubers are left uncovered) turn green and become bitter and toxic, so the crop must be kept covered with soil.
Promising A person has checked it against its sources. This one is about eating safely, not how the plant grows. The planner suggests it.
How it works
Tuber tissue exposed to light produces chlorophyll and, in that same tissue, synthesises the toxic glycoalkaloids solanine and chaconine, so soil mounded over the developing tubers keeps light off them and prevents both the greening and the toxin from forming.
What to do about it
Hill the crop. Once the stems are roughly 8-12 inches (20-30 cm) tall, draw loose soil up around the base of the plants to cover most of the stem and bury any shallow tubers, and repeat two or three times through the season so the tubers stay covered. Green tubers are bitter and should not be eaten; the green signals the toxin is present and is not reliably removed by peeling, so the defense is to keep light off the tubers in the first place, in the ground and again in dark storage.
How much it matters: No glycoalkaloid figure is stated or estimated. Greening and toxin buildup rise with the light a tuber receives and are avoided by keeping the tubers covered; because the exposure is the gardener's to control through hilling and storage, the rule only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
Tubers exposed to sunlight (both before and after harvest) will turn green and should not be eaten
Green skin occurs when potato tubers experience exposure to light
Plants it applies to
Read next
- Growing potatoes from seed tubersThe potato (Solanum tuberosum) is a nightshade, kin to tomatoes and peppers, grown from pieces of tuber instead of seed. That decides most of how you grow it.
- When to pick your harvest, and how to make it keepThe picking signs for each crop, which ones must cure before they'll keep, the three kinds of pantry, and what should never see the refrigerator.
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
- Details updated
- Wording made clearer
- Added to the rules
Cite this page
Milpa Gardens. "Potato tubers that catch light while growing (wherever soil settles or washes away and shallow tubers are left uncovered) turn green and become bitter and toxic, so the crop must be kept covered with soil." Evidence grade: Promising. https://milpa.garden/rules/potato-tubers-that-catch-light-while-growing/
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