Many gardeners have encountered rats, and urban gardeners often face this problem multiple times. The Norway rat (commonly known as the brown or sewer rat) thrives in human environments. Gardens, especially in cities, provide an ideal habitat for these rodents, offering abundant food, water, and shelter.
Why Rats Are Attracted to Gardens
Rats burrow into the soil to create nests, with garden soil being particularly attractive due to its fertility and freshness. Burrows can be between one to six feet deep, typically with an entrance, an exit, and sometimes an escape hole. Each burrow can house up to eight rats, and by counting burrow holes, gardeners can estimate the population in their garden.
However, you don’t need to resort to toxic pesticides to manage rats. Effective control starts with prevention and understanding what rats need to survive.
Eliminate What Attracts Rats
Rats require one to two ounces of food and daily access to water. They will eat virtually anything, but like most mammals, they need protein, fats, and carbohydrates, particularly for reproduction.
- Compost: While vegetable and fruit scraps are not enough to sustain a rat colony, compost piles containing table scraps, meats, grains, oils, or fats become highly attractive. Food scraps like this should never be added to a community garden compost pile. The heat generated by decomposing organic material can also provide warmth, making compost piles even more appealing during colder months. Compost must be tightly managed, including being turned regularly and covered or stored in sturdy plastic or metal bins with secure lids.
- Trash: Bags of garbage left near gardens offer a continuous food supply to rats. Trash should be stored in durable containers with tight lids to prevent access. Gardeners must ensure any food waste is cleaned up after meals or picnics in the garden. Large commercial dumpsters, often located near community gardens, likely have drainage holes typically located at the back. These uncovered holes offer an easy entry point for rats, allowing them access to a continuous food supply. If you have such a dumpster nearby, consider using a drainage plug or steel mesh to cover the holes, or request a new dumpster. In Colorado’s dry climate, the need for drainage is minimal, so covering these holes won’t impact water management but will significantly reduce rat infestations.
- Pet Food and Waste: Food left out for animals like pigeons, cats, dogs, chickens, or rabbits can inadvertently attract rats. Even animal waste, like dog feces, provides nourishment. Feeding feral cats to control rats often isn’t effective, as rats breed rapidly. While a cat may occasionally catch a rat, female rats can reproduce multiple times a year, having up to 12 pups per litter. Therefore, it’s best to avoid feeding outdoor animals where rats are a concern.
Reduce Shelter Opportunities
Rats seek out areas where they feel safe from predators. Dense vegetation, tall weeds, and clutter like lumber or rock piles provide them with ideal shelter. They often use bushes, ivy, and ground-level vegetation as cover, and prefer to travel along straight lines such as walls or fences, using their whiskers to navigate.
To deter rats from taking up residence:
- Trim back vegetation at least 18 inches away from buildings.
- Remove ivy and vines from the sides of buildings and trees.
- Keep tree branches from touching buildings, as rats can use them as bridges.
Removing clutter and ensuring the garden is neat and exposed will make it harder for rats to find safe pathways or hideouts, and they may move on to more sheltered areas.
Interrupt Rat Pathways
Rats leave behind greasy rub marks along walls, which contain pheromones used to communicate with other rats. Washing these marks with vinegar or biodegradable soap can help disrupt their established routes. Additionally, hardware cloth (half-inch mesh) can be installed along the base of walls and fences, buried 8-12 inches underground, to deter burrowing. Though rats can dig deeper, many will be discouraged by the effort.
A Simple Rat Reduction Plan
Here are steps you can take to keep rats out of your garden:
- Move compost into rodent-resistant containers with tight-fitting lids.
- Store seeds and pet food in secure, rodent-proof containers.
- Remove fallen fruit or nuts regularly.
- Clean up animal feces and food waste daily.
- Eliminate standing water and improve drainage to avoid water pooling.
- Remove clutter from sheds, garages, or outdoor spaces.
- Cut tall grass, weeds, and trim plants near buildings and walls.
Monitor and Control Rat Activity
Early spring, before planting, is the best time to inspect your garden for signs of rat activity. Look for burrow holes, droppings, rub marks, gnawed plants, and worn paths, which indicate an infestation. Check the garden perimeter a few times a week to stay on top of new rat activity. Gardeners can tell if rats have been in beds or under the shed by wadding newspaper, filling holes, and seeing if they get moved over a few days.
If you identify rats, consider using non-lethal control methods first before adding snap traps in protective boxes to ensure birds, pets, and children can’t accidentally access them. Check and reset the traps daily.
Non-Lethal Control Methods
For gardeners who prefer non-lethal methods, there are several effective options:
- Live Traps: Live traps are a humane option for catching rats. Baited with food like peanut butter or fruits, these traps allow you to capture and relocate the rodents away from the garden. However, ensure you release them far from your home or community garden, as rats can find their way back if released too close.
- Natural Deterrents: Certain scents are known to repel rats. You can plant strong-smelling herbs like mint, lavender, or garlic around the perimeter of your garden to act as a deterrent. Rats dislike these odors, and it may help keep them from nesting in the area. If there is a particular spot that you are attempting to exclude, ammonia-soaked rags work well to get rats moving from under sheds.
- Balsam fir oil in a material like sawdust has been shown to repel rats. If they are nesting under a garden shed, place some underneath. Wait about a week, then seal off all access to the space under the shed. The repellant can also be placed around the garden plots and replaced every 30-90 days.
Avoid using poison dust in burrows, as this is illegal in gardens and can be dangerous to other animals and children. Similarly, be wary of sonic devices that claim to repel rats—there’s no scientific evidence supporting their effectiveness.
