"> OMG! There are blades of grass growing in my above ground pool – Above Ground Pools Know it All

OMG! There are blades of grass growing in my above ground pool

It’s hard to believe when you first see it. You look down into your above ground pool, and at the bottom, there is what looks to be a blade of grass. It’s one very green, perfect blade of grass growing strongly out from the pool’s bottom.

Having to make sure what you see is real, you decide to get in the pool and take a closer look. As you swim down to see it up close, you verify it. It’s a blade of grass.

Nutgrass or Nutsedge is a type of grass that can grow through an above ground pool liner. Not all yards will have this type of grass, but it’s hard to identify, so treating for nutgrass prior to installing the pool’s liner is recommended for most areas.


There are many types of vegetation that will grow under an above ground pool’s liner after the pool has been installed. It’s normal to have life try to grow in the ground under the liner, but the lack of sunlight will quickly prevent everything from continuing to grow.

After a few days of this now new environment of no sunlight(underneath the liner), any vegetation still growing will die. Nutgrass won’t though. THE REASONBecause nutgrass can lie dormant for a while, and then decide to try to grow.

Nutgrass being able to lay dormant is not the whole story on its ability to survive and then grow through a pool liner. The way it grows is also a big factor.

“A newly formed blade of nutgrass is small and has a very sharp, needle-like point to it. As it grows and pushes upward, it’s needle-like top can penetrate through many tough things, including a vinyl liner.”

As this new, small blade of grass makes its way through the liner, it will now have the sunlight it needs and will continue to grow into a nice, healthy, fat, bright green, adult grass.


Under the liner, the nutgrass doesn’t have the ability to seed. It will grow up through the liner and then, that’s usually it. In most cases, pools with nutgrass will only have a blade or two grow through and that’s all.

More often, pool owners can remove the blade or two and patch the small hole they made, and they are good. In other cases though, the earth will still have some nutgrass that is staying dormant for a longer period. This will result in the pool getting more penetrating blades maybe days or weeks later.

It’s uncommon to get more blades of nutgrass growing through the liner at later dates but sucks when that happens as the pool owner is never sure if more will come.


Have you ever seen grass growing up through a road? Yeah, that was nutgrass. I bring this up because it can be no one’s fault as to why this grass grew through your pool liner. I mean, if this stuff can grow through black asphalt, what chance do you think a thin vinyl liner had of holding it back?

This article is not about how to prevent nutgrass from growing through a pool liner, but I will say this: “There is no guarantee that nutgrass won’t grow through an above ground pool liner. Thick layers of purchased sand, liner guards/pads, expensive foam sheeting, and/or nutgrass killer poison may prevent some or all from damaging the liner, but they may not too”.


So, now that you know what this grass is that has grown into your pool, you can fix the issue. Here’s how.


1 A mask and weight belt – You will need to be able to see underwater and stay down near the grass without floating up. A good mask and divers’ weight belt is ideal.

Don’t have a diver’s weight belt? Really? I thought everyone had one. LOL No problem. You can have a family member keep their foot on you while you are doing the repair, or have them hold you down from outside of the pool by pressing the pool pole against your back.

You can also let out the air in your lungs instead of holding your breath. No air in your lungs will keep you down in the water. It’s not ideal, but much better than having your body constantly floating upward while you are trying to do something at the pool bottom.

2 Roundup or Image liquid nutsedge killer and a syringe needle or ear dropper.

3 Underwater vinyl patch kit

4 Utility knife and clippers(if needed)

5 A large coin (like a quarter or bigger)


1 Using the coin, trace and cut coin size pieces of clear vinyl included in the underwater patch kit. Set them aside

2 Fill the syringe or whatever applicator you have with the liquid poison. Set aside.

3 Place all the needed materials on the top rail of the pool or where you can have access to everything once in the pool.

4 Get In the pool, put on your goggles and weight belt.

5 Locate the nutgrass/s growing at the bottom of the pool

6 Take the coin with you and make your first trip down to the blade. Pull out the blade of nutgrass from the bottom of the pool. If it won’t pull out, use clippers of some kind to cut it out. Leave the coin next to where the blade used to be(so you can find the hole later).

7 Take one of the coin-sized pieces of clear vinyl(that you made earlier) and apply glue provided in the patch kit to one side only of the piece and fold in half.

8 Immediately take the folded piece of vinyl along with the syringe and go back down to the repair site. Find the hole where the blade used to be (where you left the coin), and apply some poison into it and then patch it with the coin-sized clear vinyl piece.

Unfold the vinyl piece and press the glued side down directly over the hole. Continue to press the patch piece until it sticks very well to the pool’s liner. NOTE: You want the entire patch to stick evenly and not have any edges flapping up. This is why I use round pieces for the patch

9 The repair is complete. Repeat these steps for any other nutgrass blades in the pool.


Some nutgrass damage can be severe. I have seen a couple of pools over the years have a couple of hundred blades of grass growing through. It’s amazing to see all that grass growing in four feet of water and looking super healthy. It looks like a rice field.

If you have the misfortune of an extreme nutgrass infestation, then there’s really only one thing you can do – drain the pool and change the liner.

You could repair a hundred blades of nutgrass in a pool and it would be fine, but I don’t recommend that. One reason is that it’s too much work to do that much repairing.

The bigger reason is that your ground has too much nutgrass in it. In this case, you will probably continue to get more new growth and have to constantly repair the liner. Yikes.

It might suck bad to have to go through the expense of replacing lost water, pool chemical start-up replacement, a new liner, and maybe paying someone to replace it. But it’s better to fix this right and start fresh.


Nutgrass growing in earth made of mainly of coquina under an above ground pool
Nutgrass growing in hardy coquina soil

If you are having to replace your liner because of too much nutgrass damage, then that is extreme and must be dealt with extremely.

My advice here is to take your time. Drain the pool, cut the old liner out, treat the earth with poison, and wait. Here are some steps.

1 Drain the pool and cut out the liner

2 Pull out any visible nutgrass – If you see any blades of grass left in the earth, gently dig the blade up and see if a small nut is attached to it. If so, that’s nutgrass. Hand remove all blades and attached nuts from the area of the pool bottom.

3 Rake the entire bottom of the pool and then apply roundup – Roundup is not an ideal chemical for this, but it’s probably the best product you can use in this situation. Apply a generous amount of roundup evenly with an applicator.

4 Let the pool bottom sit for a week – Do this to wait and see if any nutgrass grows up in the next week. If you see any, get in there, dig up the nut, and remove it by hand.

5 If you had some nutgrass grow in the first week, then rake again, re-apply more roundup, and then wait another week – The idea here is to be able to remove as much nutgrass from the area as you can before installing a new liner. Since nutgrass can lie dormant, waiting helps.

6 If no nutgrass has visibly grown in the earth, you may proceed with installing the new liner. BUT FIRST

7 Purchase a granular nutgrass killer – This may be a hard product to get, but you have to have granular. The liquid killer sold at Home Depot or Lowes will not be effective over the long term. ProTeam Zapzit or something like that is what you need. Purchase enough for a DOUBLE DOSE depending on your size pool.

Remember, your situation is extreme. You don’t want any nutgrass coming through your new liner.

8 Purchase a liner pad/guard for above ground pools – A liner pad is no guarantee for preventing nutgrass from growing through a liner, but when combined with a lot a granular nutgrass killer, it helps a lot.

9 Re-smooth the pool’s bottom, evenly apply all of the nutgrass killer – You absolutely want to use an applicator for this. Spreading out this chemical by hand (like how you would feed chickens) will not make an even layer of poison.

This chemical is a pre-emergence herbicide. This means it’s designed to hang out in the earth and wait for the vegetation(nutgrass) to come to it. So, providing an even layer will make a good kill zone. The double dose of the product should make the earth look like it was hit with a snowstorm of granular chemical.

10 Install the liner guard/pad and then install the liner directly on top of that – I have noticed that some DIYers will bury the liner pad in the ground some. This is wrong, stupid, and won’t aid in creating a chemical barrier or zone to protect the liner from nutgrass trying to grow through it.

11 Fill the pool and hope – The job is done but you could, in theory, still get nutgrass. I mean, after doing all of the above, you most likely won’t. But only a concrete bottom can guarantee no nutgrass growing through a liner.


Dan writes with the knowledge of having 35 years (and counting) in the above ground pool industry.

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