Can Cat Pee Kill Plants? (And How To Get Rid Of It)

It’s one of life’s best moments to have cats around you in the garden. But your cats can also pee and mess up your plants.

Cat pee can kill plants if it’s in large amounts because it contains ammonia that is toxic to plants and beneficial organisms. A little cat pee won’t harm plants but if the cat uses the soil every day it will cause harm. The pee also contains salt that will build up in the soil and harm the plant.

I’ve written details below on what you can do to reduce the effect of such cat urine in your garden. And how you can keep your cats away from your plants.

How do you neutralize cat urine in soil?

It’s essentially the Nitrogen left in the urine after everything has passed through the cat’s kidneys that does the damage. Small amounts are a benefit to the plant, but unless you have a superbly trained cat, you will get random urine soakings. As with any form of excess – not only Nitrogen – your first step would be to soak the area in water. 

If the plant is in a pot, the initial danger is more significant, as there is far less soil to contaminate so that it can happen a lot quicker than, say, in a flower bed. Conversely, the soil in a pot is a lot easier to rinse due to the pot’s smaller size, and the danger can be swiftly averted.

Depending on the severity of the urine soaking and the size of the pot, and only when the soaking is severe, I generally stand the pot in a bucket, which I fill to a point halfway up the flower pot with tap water. No additives are necessary at this point. Remember, you are wetting the soil, for now, not trying to feed the plant.

I leave the pot in the water for five to ten minutes and then place it on a flat surface, where I begin to do the actual rinsing of the soil, using a hosepipe set to a reasonably fine spray and not very hard at all. 

I’d suggest you rinse for three or four minutes, measured once the water is coming out of the bottom of the pot. This underflow will be almost instantaneous since you have already soaked the pot in the bucket.

If the plant is planted directly into a garden bed, the situation is less severe, and I suggest you might allow a sprinkler to douse the area for 10-20 minutes.

How to Remedy the Situation After the Rinse (In a Pot)

Rinsing the soil to remove cat urine will also remove some of the nutrients, minerals, and trace elements vital for your plant’s growth. Naturally, you will need to add these back to restore the balance. If left untreated, the plant will be weak and may attract diseases, and ethylene gas and carbon dioxide might form around the roots, further endangering the plant.

Fortunately, the repair job is relatively straightforward: 

• Add fresh compost. A handful or so is acceptable in a small pot plant or two to five handfuls as the pot increases in size.
• Add seaweed extract or plant food, both readily available at your garden center. Check the labels for measurements, but if they’re organic, it’s impossible to overdose accidentally.
• Pour yourself a nice drink, take a seat in the garden and congratulate yourself on a job well done!

How to keep cats away from your plants

Some consider monkeys to be escape artists extraordinaire. Still, cats can seemingly get out of – and thus into – almost any situation, and keeping them out of your plants or veg patch can be exhausting.

Wooden poles and shade netting are a perfect solution, but unless you’re growing veg or other plants on a large scale, this might be overkill and also a zonal issue, depending on where you live.

You can, of course, purchase a commercial spray with which to spray the plants, but the idea raises two questions:

1. Is it organic (and thus not detrimental to the health of my family in the case of vegetables, etc.,) and
2. Will I have to respray every time it rains heavily?

If you’re trying to grow your own veg, you’re probably also on a reasonably tight budget, so I’d suggest you consider a cheaper option.

What smells do cats dislike? Vinegar, garlic, onions, citrus, coffee grounds, tobacco, and so many others. Figure out which of these you can live with and mix them into a spray. This spray can be applied to the foliage and the soil and monitor should the result. 

You might also toss lemon and orange peels from lunches and salads onto the soil between the plants. 

A small amount of dishwashing liquid and cayenne powder sprayed onto the foliage will also deter felines and has the bonus of smothering any aphids that might be munching under the leaves. 

Having your garden watered via a timer also keeps things interesting for unsuspecting cats looking for a place to hunker down.

What Alternatives Can I Provide?

Cat litter boxes – These do not have to be expensive, but if you are going to make your own from an old drum or similar, I would suggest using plastic. It is easily washable and does not readily absorb odors.

Make sure it is big enough for your cat/s as no self-respecting cat wants to stand in feces when squatting. Naturally, change the sand or other absorbent medium as needed. (Your nose will assist in this regard)

Al Fresco Toilet – A fancy name for an outside loo. Just loosen up sand about 12″ deep and two yards by two yards if you can spare the space. Nice, soft sand is far nicer to a cat than squatting between your raspberry bush and cactus plant, I assure you. (Make sure it’s pretty close to the cat’s usual exit from the place it sleeps)

Can cat pee ward off pests from the plants?

Yes, it can. However, I can find no research papers covering a study that shows an effect, adverse or positive, of cat urine on pests in the insect kingdom.

Animal pests are another matter entirely, and it’s a foolhardy field-mouse or vole that will hang about an area dripping in the sweet tang of your moggy’s pee. (Of course, when they move away, they only move to the closest location, not affected by the smell, and continue ravaging your carrots and tomatoes.)

The cat itself is a far more significant deterrent, so while a cat might be encouraged, his using your veg patch as a toilet is not.

I actively promote cat activity in my garden and veg patch, with several bushes of Nepeta cataria (or catnip) and several water bowls scattered around. I have had very few animal pest issues, but that’s undoubtedly due to my cats’ presence and not just their urine.