You might notice a plant poking through a crack in the concrete and find yourself wondering whether the crack was already there or if the plant broke through the concrete. Are plants strong enough to grow through the concrete, or is something else happening?
Plants can’t grow through concrete directly. However, their growth can displace the concrete, causing small cracks to appear. The plant will seek the fastest way to get to the surface and grow through those weak areas. Over time, the cracks worsen as the plants push through the opening more.
Even the smallest plants can pose a problem for concrete. You’ll want to keep reading to learn more about how these plants break through the surfaces of sidewalks and driveways. Let’s begin!
How Do Plants Grow Through Concrete?
When you see a plant growing in a concrete crack, the plant didn’t burst through and cause those cracks. There was already a gap there, and the plant growing through the crack worsened it. Most seedlings aren’t strong enough to burst through a solid concrete slab.
Even new concrete paths can have tiny cracks barely visible to the naked eye. When a plant seed gets into those cracks, it starts growing. The roots spread under the concrete until it finds a weak point to push through to the surface. This process causes the gaps in the concrete to worsen.
It may appear as though the plants are breaking through the concrete, but what happens is the plant forces itself through a crack. If this happens, it can be highly damaging to concrete surfaces as the plant grows.
Can Roots Grow Through Concrete?
Roots can grow through concrete if there are small cracks. The roots can push through these gaps and enlarge them. However, tree roots growing under concrete will cause more damage than small plants since they can push up entire concrete slabs.
So, the roots of any plant can grow through concrete, and some types of plants will be much more harmful to concrete than others. The roots won’t pierce through the concrete, but they can displace the slabs or take advantage of any tiny cracks they find.
However, you’re more likely to see a plant growing through the cracks, not the roots since they spread out under the concrete. Most plant roots will only push through the surface if the soil doesn’t drain well or becomes overly compacted, and they need more air.
It’s also worth noting that concrete dust can sometimes kill plants by changing the pH level in the soil. To know more, check out my article on the ill effects of concrete dust on plants: Will Concrete Dust Kill Your Plants?
Tree roots are much stronger than most other plants, so they cause the most problems with concrete. Even small trees can destroy a sidewalk. If you’re having this issue, you’d need to remove the tree, the old concrete, and the tree roots before leveling the slabs.
What Plants Are the Worst for Concrete?
Just about any plant can make its way through spaces in concrete. Weeds and grasses are the most damaging because they don’t give up. These plants are hardy and will eventually find a way through the cracks in your cement. They can also be challenging to get rid of.
Trees are also awful for concrete, so you must plant trees a certain distance away. A good rule is that tree species that grow up to 30 feet (9 meters) should be four feet (1.2 meters) or farther from all concrete. Larger trees should be double that distance away to prevent their long roots from reaching the concrete.
Flowers can also press through concrete cracks, but it’s less likely to happen unless you are already growing flowers somewhere else nearby. The seeds can blow into the concrete cracks, causing them to grow. Although, many garden flowers won’t be as hardy as weeds and grasses. They may not make it through the gap and can be easier to deal with if they do.
Overall, any plant can be highly damaging to your concrete paths. You’ll need to remove these plants as soon as you notice them to lessen the repairs you need to make.
How Do You Get Rid of Plants Growing Through Concrete?
You can get rid of plants growing through concrete by pulling them out and resealing the cracks or by using boiling water. Both of these methods work very well if you’re consistent. You’ll need to keep removing the plants for a few weeks to be sure they’re gone.
- First, most people remove plants by simply ripping them from the ground. The plant shouldn’t sprout again if you can get the roots out. However, removing all the roots in a single go can be difficult. So, you’ll need to check on the spot weekly and remove any new growth you find.
- Second, you can try using boiling water to kill the plants. All you need to do is pour hot water onto the plants. You want to spray as close to them as possible so that the roots die. Again, you’ll need to do this a few times over several weeks to ensure the plant doesn’t return. After the plant cools off, you can try pulling it out of the ground.
- Lastly, after you’ve got the plants out of the concrete, you’ll need to reseal the gaps with masonry caulk to ensure nothing else pops up. The caulk gun works perfectly for more minor cracks, but you may need to patch the larger holes.
If you don’t reseal the cracks, the cement will worsen as water, ice, and more plants get inside. So, it’s best to deal with cracked concrete sooner rather than later.
Watch this short YouTube video before filling the cracks using masonry caulk:
How To Deal With Returning Plants
If you have a stubborn plant that keeps coming through the spaces in your concrete, you’ll want to research it and find out its species. Most likely, it’s a weed that keeps returning, but most plants require different methods to eliminate them. Sealing the crack should kill it since it won’t be able to break through anymore.
However, you can also treat the concrete cracks with a weed killer. These solutions can soak into the soil and reach the root, so they’re often very effective. If you don’t want to use a store-bought chemical, you can also try making your own at home.
Here’s how you can make a weed killer using vinegar and salt:
- Mix a gallon (3.78 liters) of white vinegar with a cup of salt (273 g) in a large container.
- Add a cup or so of lemon juice (237 ml) and a few squeezes of dish soap to make your solution more deadly to unwanted plants.
- Stir the solution until you can’t see any salt at the bottom.
- Pour or spray the solution on the plants until they’re fully saturated. You also want the solution to seep into the soil surrounding the plant.
- Continue applying the solution to the unwanted plants for several days.
- When the plant withers, remove it from the concrete.
- Vacuum the soil and debris from the crack, then fill it with a masonry caulk.
Some plants will keep returning no matter how many times you pull them out. Usually, this means they have hidden roots under the concrete, so you’ll need to kill them using a solution like this. Commercial weed killers should also work well.
Will Plants Grow Over Concrete?
It’s also possible for plants to grow over the top of concrete. Plants will eventually make their homes there if there’s a layer of soil on the concrete slab. Their roots can reach down to the cement layer, so the ground needs to be deep enough for the types of plants that you want to grow.
Today’s concrete can break down after about 50 years. Plants can cover it to help break it down faster as their roots can push through open spaces in the slabs. Moss can grow in the soil over concrete and wear it down even faster since it holds moisture. Check out my article to know how to prevent moss growth on cement: How to Keep Moss from Growing on Cement
It’s also not uncommon to discover hidden concrete slabs on your property. As grass and other plants grow over it, it becomes completely hidden. Unless you tried to dig in those areas, you’d never know it was there. Many people discover old shed foundations and sidewalks when digging up the ground for their new projects.
Overall, plants can grow over concrete quickly. They only need a layer of soil to start taking root on the solid slabs. However, plants that require deeper roots might not be able to grow there since they can’t dig down past the concrete.
Final Thoughts
In short, plants can find even the tiniest cracks in concrete and force their way through those weak points. As they get bigger, the damage worsens. The plants aren’t bursting through solid concrete but instead push through spaces already there. This process can make it look like the plants are bursting through the surface.
Depending on the damage, you’ll want to fill in the gaps with new concrete. The plants will keep making the cracks worse over time, so you need to replace the concrete entirely. It’s easier to repair the earlier you catch the damage.
