Rodents may eat seeds and young sprouts, and enter grow spaces for food, water or shelter. The best protection is simple: seal every gap over 1/4 inch (the opening size UC IPM gives for mice) with metal mesh or sheet metal, clean up food sources, and use snap traps placed out of reach of pets and kids.

Mice and rats are a common problem in garages, sheds, basements and outdoor gardens. Below, we answer whether mice like weed, show the signs of rodents, and walk you through sealing them out, cleaning up and trapping safely.

Do mice like weed? What rodents actually go after

Mice and rats are not drawn to cannabis because it is cannabis. They are looking for food, water and shelter, and a grow space can offer all three. The California Department of Pesticide Regulation lists mice and rats as pests that eat young sprouts and seeds in its California guidance on legal pest management for cannabis growers.

That makes seeds and seedlings the most at risk. A tray of freshly sprouted seedlings is an easy meal, and a bag of seeds left on a shelf can disappear overnight. Rodents may also chew stems, dig in pots, or nest in warm spots near lights and equipment.

Grow spaces attract them for other reasons too. Bags of soil, organic amendments and spilled nutrients can smell like food. Water trays and reservoirs offer a drink. Clutter, stacked bags and the warm space around a tent offer shelter. Remove those draws and you remove most of the reason rodents come in.

Signs you have rodents

Look for droppings first. Mouse droppings are small and pointed, while rat droppings are larger. You will often find them along walls, under benches and near food.

Other signs include chewed seedlings, stems cut cleanly near the soil, gnaw marks on bags, containers or wiring, and shredded paper or fabric used for nests. You may notice holes dug in pots or soil scattered on the floor. Some growers hear scratching at night or find greasy rub marks along walls where rodents travel.

If you see one sign, check the rest of the space too. Rodents rarely come alone.

A simple way to confirm activity is a tracking test. Sprinkle a thin layer of flour or talc along a wall where you suspect traffic and check it the next morning. Small footprints or tail drag marks tell you where rodents run, which is exactly where to place traps and where to look for a nearby entry point.

Seal them out

Keeping them out is the most important step. UC Statewide IPM explains that “mice can enter through openings as small as 1/4 inch,” and advises sealing small cracks and openings using wire screen or coarse steel wool. That 1/4 inch figure applies to mice. Rats need larger openings, so sealing anything over 1/4 inch with metal mesh or sheet metal covers both.

Material matters. UC IPM warns that “rats can chew through plastic, foam, wood, and caulk.” The Cannabis Industry Journal adds that caulk, mortar and spray foam offer almost zero protection against the gnawing power of rodents, and that steel wool will eventually rust and break down. Use metal mesh, hardware cloth or sheet metal for lasting repairs, and use foam or caulk only as a filler behind metal, not on its own.

Go over the whole space. Look where pipes and wires enter, under doors, around vents, along the bottom of walls, and at gaps in garage doors. Fit door sweeps and cover vents with metal mesh.

Don’t forget the grow equipment itself. Ducting ports, fan openings and gaps where cords enter a tent can all give a mouse a way in once it is inside the room. Keep tent zippers closed, cover intake ports with fine metal mesh, and lift bags and pots off the floor on shelves or racks so you can see underneath. A tidy floor makes new droppings easy to spot.

Clean up

A clean space gives rodents fewer reasons to stay. Store seeds, soil, amendments and nutrients in sealed, hard containers such as metal bins or thick plastic tubs with tight lids. Sweep up spilled soil and plant waste after each session, and do not leave pet food or other snacks near the grow.

Cleaning up droppings needs care. Wear gloves, wet the droppings with an EPA registered disinfectant per its label, then wipe and bag the waste. Wetting first keeps dust down. Wash your hands well when you are done.

How to rodent proof a grow, step by step

1. Look for droppings, chewed stems and nests.
2. Find and seal every gap over 1/4 inch (the mouse size from UC IPM) with metal mesh or sheet metal.
3. Store seeds, soil and nutrients in sealed hard containers.
4. Clean up spilled soil and plant waste.
5. Clean up droppings safely: wear gloves, wet the droppings with an EPA registered disinfectant per its label, then wipe and bag the waste.
6. Set snap traps along walls where you see activity, out of reach of pets and kids.
7. Check traps and seals every week.

Seedlings deserve extra protection. Cover trays with a fine metal mesh cage until plants are bigger and less tempting.

Trapping safely

UC IPM notes that for mice, snap traps work well and are a great first step. Place them along walls, behind objects and near droppings, since rodents tend to run along edges rather than across open floors. Set the trigger end toward the wall. Use several traps rather than one.

Keep traps out of reach of pets and kids. Put them inside a covered box or a trap station with a small entry hole. Check them often and wear gloves when you empty them.

Avoid poison baits around your grow. In California guidance, the California Department of Pesticide Regulation notes that some rodenticides should never be used in or around cannabis cultivation sites. Poisoned rodents can also die in walls or be eaten by pets and wildlife. Rules on rodenticides differ by state, so check yours. For outdoor gardens, the same California guide lists practices such as chicken wire fencing, traps and barn owl boxes.

For more ways to protect your plants, see our guide to protecting marijuana plants from pests at https://kindseed.com/7-ways-to-protect-marijuana-plants-from-pests/.

Troubleshooting

Sign	Likely cause	What to do
Seedlings chewed off	Mice or rats	Protect seedlings with mesh and trap
Droppings near the tent	Active rodents	Seal gaps, set traps along walls
Holes reappear	Soft fillers like foam	Use metal mesh or sheet metal
Traps catch nothing	Wrong spot	Move traps to walls and runways

If rodents keep returning after you have sealed and trapped, there is likely an entry point you missed. Check again at night with a flashlight, and look high as well as low, since mice climb well.

Sources: UC Statewide IPM Program, House Mouse (https://ipm.ucanr.edu/home-and-landscape/house-mouse/). UC Statewide IPM Program, Rats (https://ipm.ucanr.edu/home-and-landscape/rats/). California Department of Pesticide Regulation, Legal Pest Management Practices for Cannabis Growers (https://www.cdpr.ca.gov/wp-content/uploads/2024/11/attach1502.pdf). Cannabis Industry Journal, Comprehensive Rodent Exclusion.

FAQ

Do mice like weed?

Mice are not drawn to cannabis itself. They look for food, water and shelter. In a grow, they mainly go after seeds and young sprouts, and they may nest in warm, cluttered spaces. Sealing gaps and storing seeds and soil in hard containers removes most of the draw.

Do rats eat cannabis plants?

Rats may eat seeds and young sprouts, and they can chew stems, pots and equipment. Larger plants are less at risk, but rats can still damage a grow. Seal gaps over 1/4 inch, the opening size UC IPM gives for mice, with metal and use traps placed out of reach of pets and kids.

Will peppermint oil keep mice away?

Scents like peppermint oil are not a proven way to keep mice out. UC IPM’s advice is to seal gaps and use traps. Focus on blocking entry points with metal mesh or sheet metal and removing food sources.

Is rodent poison safe near a grow?

Avoid it around plants, pets and kids. California’s pesticide agency bars some rodenticides at cannabis sites, and rules in other states differ, so check yours. Snap traps in covered stations are a safer first step.

How do I protect outdoor plants?

Use metal mesh cages around seedlings and fencing such as chicken wire around beds. Keep the area tidy, store soil and seeds in sealed containers, and use traps in covered stations. Some growers also put up barn owl boxes.