Practice

Low Tunnel

Also known as: caterpillar tunnel, hoops and row cover

A bed-scale season-extension structure: a series of low hoops (typically PVC, wire, or fiberglass rod) over a single bed, covered with row cover fabric or thin greenhouse plastic. Smaller, cheaper, and more flexible than a [[hoop-house|hoop house]]; provides 4–8°F of warming and substantial wind protection. Coleman calls it 'the cold frame at field scale.' The standard mid-tier season-extension tool: more protection than a row cover laid directly on plants, less commitment than a walk-in tunnel.

A low tunnel is the simplest way to add several weeks of season extension to a single bed without a major structural commitment. Half-inch PVC pipe or fiberglass rods bent into 4-foot arches, stuck into the ground every 4 feet along a bed, covered with row cover fabric or thin plastic, weighted at the edges.

Time to build: about thirty minutes per bed. Cost: $20–$60 per bed depending on materials.

What it does

4–8°F of frost protection with row-cover fabric; more with plastic.
Wind block — significant.
Insect exclusion — when used with fine row cover (Reemay 0.5–1.0 oz), excludes cabbage moths, flea beetles, cucumber beetles, squash vine borers.
Animal protection — surprisingly effective against rabbits and casual deer browsing, less so against determined deer.

When to use it

Spring: install in March; plant cold-hardy crops (lettuce, peas, brassicas) 3–4 weeks before the conventional last frost date.
Summer: replace fabric with shade cloth in hot regions; protect heat-stressed greens.
Fall: extend the harvest of cold-hardy crops 4–6 weeks past first frost.
Winter: under deep cold (zone 5 and colder), low tunnels alone are usually not enough; pair with row cover laid directly on plants inside the tunnel for a double layer.

The caterpillar-tunnel variant

A larger semi-permanent low-tunnel form — typically 10–14 feet wide and walk-into-it tall, supported by sturdier hoops, with side walls that lift for venting. Jean-Martin Fortier popularized the format for small-scale commercial production; intermediate between a low tunnel and a hoop house in commitment and cost.

Practical notes

Edge sealing matters. Wind under the cover defeats most of the benefit. Bury edges in soil, or weigh down with rocks, sandbags, or boards.
Open on warm days. Even row cover can overheat in spring sun; vent ends or lift one edge.
Hoop spacing — closer in windy or snowy sites; standard is 3–4 feet apart.
Materials — fiberglass rods last longer than PVC, but PVC is cheaper for starting out.

Sources

Eliot Coleman, The Winter Harvest Handbook (Chelsea Green, 2009)
Jean-Martin Fortier, The Market Gardener (New Society, 2014) — caterpillar-tunnel format

Rooted in life.

What links here, and how

Inbound connections from across the wiki, grouped by lens and by relationship. These appear automatically — every entity page declares what it links to, and that data populates here on the targets.

Practical

shares approach with

Row Cover row cover laid directly on plants is the simplest form; the same fabric over hoops becomes a low tunnel

1 inbound link · 3 outbound