A young transplant can be cut off at the soil line overnight by a cutworm - a caterpillar that curls around the tender stem and severs it just above the ground. A collar around the stem blocks it.
Promising · suboptimal if ignored → advise
How it works
Cutworms are the soil-dwelling caterpillars of several night-flying moths. They feed after dark, curling the body around a seedling's stem and chewing through it at or just above the soil surface, which topples the whole plant. A young transplant is vulnerable because its stem is small and tender; as the plant grows the stem thickens past what a cutworm can encircle and cut, so the risk is an early-season one. A collar - cardboard, stiff paper, or foil - set around the stem and pushed into the soil is a physical barrier the cutworm can neither climb over nor tunnel under to reach the stem.
What to do about it
Around each new transplant, set a collar of cardboard, folded paper, or foil a few centimetres tall, with one edge pushed a few centimetres into the soil and the rest standing above it, so the cutworm cannot get over the top or under the bottom to reach the stem. Once the stem thickens the collar can come off.
How much it matters: No incidence figure is stated or invented. Cutworm pressure is local and episodic, and the collar is a cheap preventive for the early-transplant window, which is why the rule advises rather than warns.
The evidence
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
UMN Extension, 'Cutworms', extension.umn.edu/yard-and-garden-insects/cutworms (read 2026-08-21): 'Cutworms curl their bodies around the stem and feed on it. This feeding causes the plant to be cut off just above the soil surface'; 'New transplants or young plants have more chances of injury because their stems are smaller and more tender'; 'Place aluminum foil or cardboard collars around transplants. This creates a barrier that stops cutworm larvae from feeding on plants'; 'Place the collars around plants such that one end is pushed a few inches into the soil, and the other end extends several inches above ground.'
Univ. of Illinois Extension, 'Cutworm', extension.illinois.edu/insects/cutworm (read 2026-08-21): 'older caterpillars eat through the stem of young plants about 1/2 inch above ground and then eat the plant'; 'Collars of cardboard, aluminum foil, or metal can be placed around transplants at planting to prevent feeding'; 'older plants with thicker stems are less susceptible to attack.'
Where this rule stops
A STANDING EARLY-SEASON TRANSPLANT ADVISORY (trigger.kind always, like another rule here/115), so it surfaces on the species pages and can be cited by the transplanting guides. It gates nothing and docks no score - the app cannot know a garden's cutworm pressure - it is preventive practice. The risk is specific to YOUNG transplants with tender stems; both sources note that older, thicker-stemmed plants are safe.
Change history
Every change to this rule is one commit. This is what the project's version history records — the date and the reason — not a summary of it.
- a collar guards a young transplant against cutworms (verified)
Cite this page
Milpa Gardens. "A young transplant can be cut off at the soil line overnight by a cutworm - a caterpillar that curls around the tender stem and severs it just above the ground. A collar around the stem blocks it." Evidence grade: Promising. https://milpa.garden/rules/young-transplant-can-be-cut-off-soil/
A garden-planning corpus: 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.