Cannabis & HempPest Control

Protecting Outdoor Marijuana Plants from Mammals and Rodents

Imagine you have spent hours and hours finding and preparing a site for you to securely and successfully grow your marijuana plants. Your seeds germinated, and your plants are now maturing and healthy, and you are having visions of beautiful, flowering plants that will produce an amazing harvest. You can finally sit back and relax, enjoying the fruits of your labor.

Then you return to your site one day, only to be confronted with a horrible site: chunks missing out of your plants’ stems, leaves disappeared or lying half-eaten on the ground, the soil disturbed and dug up. There is only one way to explain this sight: animals.

It is yet another thing to think about, but it is equally important to be proactive about potential pests. The payoff of having safe, undisturbed plants is huge – they won’t waste valuable energy growing back leaves that have been eaten off, or repairing a damaged stem. If worse becomes worst, the plants could even die, meaning all your hard work and profitable crop is lost completely.

Young marijuana plants that have not yet grown a hard, protective stem are at a constant risk of being destroyed by critters like rodents, rabbits and raccoons that might be passing through and looking for a tasty snack. Because the plants are so delicate, and because these animals are so crafty, you might need to take some extreme measures to prevent them from eating up your crop. Depending on where you are located, you could have problems with animals with each animal presenting its own set of issues.

Preventing Animal Damage

The way to prevent burrowing animals is to form some sort of shell around the bottom of the plant’s stem. You could use a coffee can that had both ends removed or any other object that can form a hard barrier. This should prevent most burrowing creatures from getting to the plants.

Unfortunately growing the plants in a pen constructed of chicken wire won’t work for cannabis growers because of security issues but using a coffee can is a highly effective alternative. It is not as visible from far away, and it is also inexpensive and simple. You have to make sure you do it early in the plant’s life, however, or else it will become dangerous when you’re placing it since it could accidentally cut the stem.

Rabbits love to trample and eat leafy plants that they come across. Luckily, there are some easy ways to prevent this without also attracting human attention to your grow site. To keep rabbits away, try purchasing blood meal powder. Sprinkle it around the plants and grow area to repel animals that live above ground. The only issue with blood meal powder is that it could draw in carnivorous animals that could damage the plants when they dig in search of flesh to eat.

To prevent both the herbivores and carnivores from taking an interest in your plants, try pouring urine from a predatory cat (i.e. lions or mountain lions) around the plants. This will repel small mammals as well as deer, which smell the urine and instinctively identify it as a predator’s urine, so they stay away. You can buy this kind of urine in a nursery or online.

Identify the Problem

If you do experience some sort of pest problem, first remind yourself not to panic. You need to be cool-headed when inspecting the damage, as it is the only evidence you have for what kind of animal you are dealing with. You need to be able to identify which animal is causing the problem since that will help you know exactly how to deal with the issue.

Don’t assume the damaged plants are finished until after you have surveyed the damage. Unless they are clearly wilting because of the damage, they will probably solve the problem on their own and heal as they grow older. If the damage is more superficial, don’t be concerned at all – new leaf growth is a constant in the plant’s life anyway, as it wants to get more sun exposure throughout its life to perform photosynthesis.

Stopping a Pest Invasion

A way of stopping the problem before it starts is to become familiar with the naturally growing plants in the area. It is possible that they are also infested with some sort of pest, which could mean those pests might stumble across your cannabis plants and have an entirely new source of delicious food. You can use information, such as the types of plants and the type of damage they are experiencing to figure out which pests are causing the problem, and how to prevent them from getting to your plants too.

If the problem becomes too much to handle, and chemical insecticides appear to be the only way, make sure you inform yourself about the benefits and unnecessary damage that comes with using each product. The problem with chemical insecticides is that they don’t kill specific species – they simply kill anything, including insects that are advantageous to plant growth, along with harmless mammals that live near that location.

The chemicals can also have a negative effect on your own health. This means that you have to be very careful when spraying insecticides and when harvesting. Make sure the chemically active period has already come to an end before harvesting the crop. This should be obvious when you buy the product, as it is information that should come from the manufacturer, but as with any product you should do your own additional research to ensure the safety and effectiveness. New studies are always being done and they may contain new information that is different from what is in the existing studies.

Whatever your preferred form of preventing or fighting against harmful pests, if you do it correctly you shouldn’t be confronted with too much trouble. The key is to always be observant, informed, and proactive.

Gophers and Moles

One of these two underground rodents presents some potential problems. Anytime you have a burrowing critter; there is the risk of root damage. Fortunately, most of the time, moles have no interest in cannabis and stay clear root systems. In fact, moles can offer benefits to your cannabis: they’ll aerate the soil and eat any insects they can get their paws on. In general the mole is nothing to worry about because he will just create his tunnel around the roots of a cannabis plant. Moles have little to no interest in cannabis plants since the roots aren’t food for them. Gophers, on the other hand, are bad news. Gophers will seek out the cannabis roots and eat them. Left unchecked, they have been known to pull entire plants down into their tunnels.

Solving Gopher Problems

Signs of a gopher problem include:

  • The roots of a plant or plants are chewed away
  • An entire plant or plants are missing
  • Gopher mounds nearby

You can deal with gophers in a lot of different ways. If some gophers take up residence near your crop, you can try to encourage natural predators in the area. Predatory birds such as hawks and owls are natural enemies to gophers. If they are around, they will always be on the lookout for gophers and will not hesitate to take action.

You can deal with them humanely by pouring castor oil or garlic into the opening of their mound to try to force them off to another area. You can also try planting oleanders in the cannabis garden since they are toxic. But do this with caution because oleanders can possibly poison humans and any other non-harmful animals that come in contact with it. As a last resort, you can always set traps for gophers.

Solving Deer Problems

Cannabis plants are at the greatest risk of deer damage before they have matured. This is simply because the cannabinoid levels of your plants increase as they get older. Almost all herbivores (except deer) therefore dislike the taste of marijuana plants; deer like it just fine until the plants have reached their peak levels of cannabinoid, making the taste unpleasant to even the deer. You therefore simply need to keep your plants until the point when they have reached maturity – then you can rest easy knowing that the deer are no longer a threat.

If the plants are out in the open, it’s unlikely that deer will ever make it to your garden – and if they do, you will most likely see them. If, however, your plants are located somewhere with dense tree cover, you may encounter a deer problem.

Signs of a deer problem include:

  • Hoof prints
  • Deer droppings
  • Leaves missing
  • Buds missing
  • Seedlings missing

Deer are nocturnal and are therefore most likely to come to your garden in the middle of the night when fewer humans are walking around. If they do stumble upon marijuana plants, they will have a heyday, devouring plants’ leaves buds, and entire seedlings.

The only way to handle a deer problem is to use any means necessary to keep them away to begin with. If they do discover a growing operation and get the chance to eat to their hearts’ content, they will cause some serious damage to the plants.

The first preventive measure is to install a fence around the growing operation. The fence should be at least eight feet high and constructed out of durable, sturdy materials. Deer generally don’t jump higher than six feet, but occasionally jump as high as eight feet if they panic. Deer are quite nimble so make sure there is no room between the slats that allow the deer to slide through or crawl underneath the fence.

A second fencing option is to use an electric fence. Some people “train” the wild deer in the area by putting peanut butter on the wire or on a foil tag that is attached to the electric part. When the electric current is turned on, the deer will experience a shock when they try eating the treat. One or two of these shocks will remind them not to try again, after which your crop is likely safe.

You can also take advantage of the fact that deer are easily spooked. The sudden appearance of bright light will scare deer. Some growers, therefore, equip their growing operations with motion sensor lights, placed in specific spots. Placing too much light on the plants could disrupt the timing the plants’ natural life cycle. Make sure they are carefully placed and pointed away from the plants but still low to scare the deer away. Another option is to use something referred to as a “scarecrow sprinkler,” which blasts an intruder with sudden, high-pressured water.

If you don’t have the time, money, or energy to utilize one of these techniques, there are some other options available that are inexpensive or completely free. Deer have a strong sense of smell so repellents with specific scents can be quite effective. For instance, they hate the smell of human hair. You can, therefore, take hairs from your hairbrush and sprinkle them all over grow area and even on top of the plants.

Predator urine can help. You can buy coyote, fox, or bobcat urine online, and then follow the directions for how to apply it. This will need to be done again every time it rains. Deer also dislike the smell of rotten eggs, so try mixing 2 parts egg and 8 parts water, then drench the plants with it. You can also try the vampire approach and place crushed garlic in nylon socks, and then hang the socks trees around growing area. Scented bar soap is also an option – just drill a hole in it, add in some fishing line, and tie it up next to your plants. Fabric softener sheets hung from trees is also effective, as are moth balls placed in a nylon stocking and hung up.

Deer will adjust and get used to whatever smell you’re using, so switch it up every so often to help keep them away. The best approach is to combine this with motion lights or sprinklers, just to make sure.

Background information for this story was provided by Robert Bergman from

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