Don't plant anything sensitive to walnut toxin
Don't plant anything sensitive to walnut toxin (juglone) within a walnut tree's root zone. Nightshades are sensitive, and so are apple and cabbage.
As recorded: Do not plant a juglone-sensitive species within the root zone of Juglans. The plants that count as sensitive come from the walnut hazard's own list, which is wider than the Solanaceae. It also carries apple and cabbage.
Well established A person has checked it against its sources. If you skip this, the planting fails. The planner won’t allow it.
How it works
Juglans roots exude hydrojuglone, oxidized to juglone, a respiration inhibitor. The nightshades are highly sensitive; they wilt and die.
What to do about it
Plant it outside the walnut's root zone, which takes in the whole drip line and beyond. There is no soil treatment for juglone.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
Vegetables such as tomato, potato, eggplant and pepper ... are particularly sensitive to juglone
… members of the tomato family (tomato, potato, eggplant, pepper).
Plants it applies to · 5
Fruiting vegetables · 4, Roots & tubers · 1
Roots & tubers · 1
Plant teams that rest on it
- Blackberry hedge
- Blueberry ring
- Currant ring
- Fruit tree ring
- Fruit tree ring (dwarf)
- Grape arbor
- Kiwi arbor
Read next
- What the evidence says about companion plantingMost companion-planting chart entries are tradition, and few were ever tested. Here's the short list of pairings that hold up, the famous ones that don't, and how to tell which is which.
- Do plants really affect their neighbors? Allelopathy, living mulch, and what the evidence supportsSome plants do change the ground for the ones beside them, and one will kill your tomatoes. The real effects look nothing like the companion chart.
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Sources updated
- Sources updated
- Wording made clearer
- Wording made clearer
- Wording made clearer
- Advice on what to do added
- Details updated
- A person read the sources and confirmed it
- Added to the rules
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Cite this page
Milpa Gardens. “Don't plant anything sensitive to walnut toxin (juglone) within a walnut tree's root zone. Nightshades are sensitive, and so are apple and cabbage.” Evidence grade: Well established. https://milpa.garden/rules/do-not-plant-juglone-sensitive-species-within/
A garden planner built on graded evidence. Every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.