Cutworm Collars That Actually Protect Seedlings
A cutworm collar is one of those garden fixes that looks almost too simple to work—until you wake up to a row of tomato seedlings lying flat on the soil, each stem cleanly clipped near the base. That neat, angled-looking cut is the giveaway. Rabbits chew higher up and leave rough damage. Slugs rasp leaves. Cutworms usually work at night, right where the stem meets the ground.
I use collars when I am planting anything with a tender stem: tomatoes, peppers, brassicas, beans, squash, and young flowers. They are especially worth the few minutes of effort in beds that were lawn, weedy ground, or covered with mulch before planting. Cutworms hide in that kind of cover during the day and feed after dark.
The collar does not need to be fancy. It needs to do two things: extend below the soil surface so the worm cannot curl around the stem underground, and stand above the soil far enough that it cannot simply climb over it.
The best materials are usually already in the recycling bin
For most seedlings, a short cylinder about 3 inches wide and 3 to 4 inches tall works well. The material should be stiff enough to hold its shape after watering but not so rigid that it is awkward to remove later.
- Paper towel tubes work well for tomatoes, peppers, broccoli, cabbage, and kale.
- Toilet paper tubes are useful for smaller plants, but they are short, so they need to be buried less deeply or joined with another piece of cardboard.
- Plain brown cardboard cut from a box is inexpensive and easy to size for unusual seedlings.
- Thin plastic nursery pots with the bottoms removed make durable collars for areas with heavy cutworm pressure.
- Wax-free paper cups can work in a pinch, provided the bottom is removed and the cup is split if needed to fit around a larger transplant.
Avoid glossy cardboard, heavily printed packaging, and cardboard treated to resist moisture. Plain corrugated box cardboard is the better choice. It softens over time, which is fine; by the time it starts breaking down, a healthy seedling usually has a tougher, thicker stem.
How to make a simple collar from cardboard
For a transplant already in a pot
Cut a strip of plain cardboard about 10 to 12 inches long and 4 inches tall. Roll it into a loose tube around the seedling’s root ball, leaving roughly 2 to 3 inches across the inside. Secure the overlap with a small piece of masking tape, a staple, or a folded tab cut into the cardboard.
Plant the seedling first, then press the collar into the soil around it. The collar should sit about 1 inch below the soil and 2 to 3 inches above it. Firm the soil against the outside edge. Do not pack soil tightly against the plant’s stem inside the collar.
For a seedling already planted
If the plant is already in the bed, cut one straight slit down the side of the cardboard tube. Open it, place it around the stem, overlap the slit, and push the bottom edge into the soil. This is useful when you spot cutworm damage after planting and want to protect the survivors immediately.
A collar should fit around the plant, not squeeze it. Leave enough space for watering and for the stem to thicken over the next few weeks.
The depth matters more than most people think
The common mistake is setting a collar on top of the soil like a tiny fence. It may block a crawling cutworm, but it will not stop one moving just under the surface. Cutworms often stay shallow during the day, and they can tunnel or curl around an unburied barrier.
Push the collar at least 1 inch into the soil. In loose, sandy beds or in a garden where seedlings have been cut off repeatedly, go closer to 1 1/2 inches. You do not need to bury half the collar. The point is to create a continuous barrier at the soil line.
Do not make the collar excessively tall, either. A 6-inch cardboard tower around a 3-inch pepper plant holds shade and moisture around the stem, makes it harder to inspect the plant, and catches wind. Three inches above ground is plenty for ordinary cutworm protection.
What a real cutworm problem looks like
One May morning, I found four freshly planted Roma tomatoes down in a 12-foot bed. They had been planted at 6 p.m. the previous evening, looked perfect at sunset, and by 7 a.m. their stems were severed about a quarter-inch above the soil. The plants had not wilted first; they were simply toppled over. When I scratched around the soil beside one stem, about an inch deep, I found a gray-brown cutworm curled into a C-shape.
That is the moment to collar every vulnerable transplant in the bed, not just the damaged ones. Replace plants if you want, but protect the replacements before the next night. One cutworm can damage several seedlings, and fresh transplants are easy targets.
Quick identification list
- Seedling stem cut cleanly at or just below soil level: likely cutworm.
- Leaves missing with slime trails: likely slugs, not cutworms.
- Stem chewed higher up with scattered droppings: inspect for caterpillars or larger pests.
- Plant collapsed but stem remains intact and dark at the base: suspect damping-off disease or stem rot.
- Plant looks healthy but leans slightly after watering: often normal settling, not pest damage.
When collars are not necessary
Not every bent or damaged seedling needs a collar. A tomato transplant that leans after a hard rain, especially in freshly loosened soil, is not evidence of cutworms. Gently firm the soil, stake it if needed, and check the stem. If it is uncut and green, leave it alone.
Collars are also less important once plants have developed thicker, woody, or fibrous stems. A tomato that has been growing strongly for three weeks and has a pencil-thick lower stem is far less appealing and harder for a cutworm to sever. At that stage, removing soggy cardboard collars can improve airflow around the plant.
The non-obvious part is that mulch can change the equation. Mulch is excellent for moisture and weed control, but a thick layer placed right against new transplants gives cutworms a sheltered route. Keep a bare ring of soil about 2 inches wide around a newly collared seedling for the first couple of weeks, then pull mulch back in once the plant is established.
A practical planting routine
If cutworms have appeared in your garden before, make collars before planting day. It is much easier to prepare twenty cardboard rings at the kitchen table than to cut them in frustration after losing seedlings overnight.
- Make collars 4 inches tall and wide enough for the mature lower stem.
- Plant the seedling at the proper depth.
- Set the collar 1 to 1 1/2 inches into the soil.
- Leave 2 to 3 inches above ground.
- Water the soil around the outside of the collar and check that it has not lifted.
- Inspect seedlings the next morning for the first three nights.
- Remove or loosen collars once stems are sturdy and the cardboard begins to stay wet.
Cutworm collars are not a glamorous garden tool, but they are cheap, fast, and remarkably reliable when installed properly. A few pieces of cardboard can save the plants you waited weeks to grow, which is a very good trade for ten minutes of prep.
