A lightweight fabric floating row cover laid over a bed at planting keeps flying and egg-laying pests off the crop through its vulnerable early stage - flea beetles, cabbage moths and loopers, cucumber beetles and squash bugs, and the root-maggot flies of cabbage, onion, and carrot - but it must come off at flowering for any crop that needs an insect to set fruit, or it excludes the pollinator too.
Promising · suboptimal if ignored → advise
How it works
Floating row cover is a gauze-like spun sheet laid loosely over the crop and sealed at its edges to the soil, and it stops damage by physical exclusion - the adult insect cannot reach the plant to feed or lay eggs - so the barrier must be continuous from planting, before the pests arrive, with its edges buried against a walking insect; because the same closed barrier also shuts out the bee, a crop whose fruit depends on insect pollination has to be uncovered once its flowers open.
What to do about it
Cover the bed at planting with the crop still small, drape the fabric loosely with slack to grow into rather than tight, and bury or weight every edge so the perimeter is sealed. Leave it on through the early weeks when the pest is active. For a crop that needs insect pollination to fruit - squash, cucumber, melon, pumpkin - remove the cover once female flowers begin to bloom so pollinators can reach them; leafy greens, roots, brassicas grown for heads, and self- or wind-pollinated crops can stay covered to harvest. Where the target pest overwinters in the soil under the bed (root maggots, flea beetles, Colorado potato beetle), cover a bed that did NOT grow the same crop, or the pest emerges trapped inside.
How much it matters: No exclusion percentage is stated or invented. The protection is near-total while the barrier is intact and sealed and nil wherever there is a gap or once it is removed at flowering; because the outcome depends on timing and edge-sealing, both the gardener's to control, the rule advises.
The evidence
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
UNH Extension, 'Using Row Covers in the Garden', extension.unh.edu/blog/2020/10/using-row-covers-garden (read 2026-08-21): 'row cover can create a barrier around your plants to exclude insects, as well as some animals like rabbits, birds and deer'; brassicas - 'cabbage maggots, cutworms, flea beetles, cabbage loopers, cabbage worms'; cucurbits - 'cucumber beetles, squash bugs, squash vine borer'; 'For insect pollinated vegetables, like the nightshades ... and cucurbits ..., row cover should be removed when female flowers bloom so as to allow pollination to occur.'
UMD Extension, 'Row Covers', extension.umd.edu/resource/row-covers (read 2026-08-21): floating row cover is used to 'exclude large and small animals, especially insect pests, making it an exceptional organic pest management tool'; 'Some pests overwinter in the soil near host plants, emerging the following spring under a cover. (Examples include the adult flies of root maggots, flea beetles, and Colorado potato beetles.)'; 'Crops that don''t need their flowers pollinated by insects, like spring leafy greens and green beans, can be kept covered until harvest.'
Where this rule stops
A STANDING CULTURAL ADVISORY (trigger.kind always, a physical-barrier sibling to the collar another rule here and the seed-starting another rule here/115), so it surfaces on the species pages and can be cited by the pest and planting guides. It gates nothing and docks no score - the app cannot know whether a bed is covered - and it carries its own limit in-rule: for an insect-pollinated crop the advice to cover is conditional on uncovering at flowering, stated rather than advising a cover that would prevent fruit set.
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.
- floating row cover excludes pests - remove at flowering for pollinated crops (verified)
Cite this page
Milpa Gardens. "A lightweight fabric floating row cover laid over a bed at planting keeps flying and egg-laying pests off the crop through its vulnerable early stage - flea beetles, cabbage moths and loopers, cucumber beetles and squash bugs, and the root-maggot flies of cabbage, onion, and carrot - but it must come off at flowering for any crop that needs an insect to set fruit, or it excludes the pollinator too." Evidence grade: Promising. https://milpa.garden/rules/lightweight-fabric-floating-row-cover-laid-over/
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.