Killer Roots - Punching holes in liner

Like all the myths I discuss please feel free to point all examples where I'm in error. I'm more than happy to improve the information. But please, let's stick to actual data and references to published papers.

Short story

It's a myth. Roots do not have sharp points being pushed through soil and liners. It is no more possible for a root tip to grow through a liner than it is for you to shove your head through a 16" thick concrete wall.

Claims of people who have seen roots do this are using their imagination to say how this happened. It's not that they shouldn't believe their own eyes, it's their brains they shouldn't believe.

Long story

For people waiting at the DMV, dentist office, cable dude, and this is the only reading material you have, enjoy the rest of this page.

Pretty safe to say virtually all people in the industrialized world have an extreme fear of roots. Even people who have lived in a city their entire lives will tell people about how roots can bust through concrete and destroy whole worlds. With great conviction. At least that's the way it seems sometimes.

At the pinnacle of this hysteria is a single word...bamboo. The most feared word in imagined plant world. Well the many myths about bamboo will have to be covered another day. We're here today to consider whether pond liners can be damaged by any kind of root, bamboo included.

When roots can punch a hole in a liner.

Many myths are based on some fact. It is 100% true that cut roots sticking out of a pond wall can punch a hole in a liner. It is best to cut these roots at least an inch back into the soil. And underlayment can add protection if desired. This is true for anything sticking out of the soil. Rocks, broken glass, old pipes, you name it.

However, as this gets told and re-told some people seem to read this as "It is 100% true bah bah roots bah bah bah bah bah bah can punch a hole in a liner." and they will repeat this "fact" over and over. That's the internet. That's how myths are created.

But can a root actually grow through a liner? Nope. And here's why.

Step 1: Understanding how a root grows.

Here is a close up of a root tip from Wikipedia.

It grows like a wedge. New cells grow at the tip to move outward but the real work is done by expanding the diameter, In the picture the tip gets wider, pushing out to the left and right in the picture  like a plow opening a space new cells at the tip can freely grow into. The tip doesn't push forward, the diameter pushes outward. That's key to understand why a root can't push through a liner.

Most people seem to think the tip of the root is like a sharp spear being pushed through the soil, and through liners, concrete, whatever. But that's not true at all. The tip of a root is extremely fragile, it isn't pushed through the soil. It couldn't survive the punishment even if it could be pushed.

Roots don't grow out randomly and just get lucky. Turns out they're much more clever. According to published works by the John Innes Centre in the U.K., like Root hairs: development, growth and evolution at the plant-soil interface and others, there are little hair like deals on roots that can sense calcium uptake. Uptake of calcium requires water so these hairs can tell which direction to grow is best and the root grows in that direction. So when one of these hairs makes contact with a rock, or a liner, there is no calcium uptake and that hair doesn't grow in that direction. Other hairs will sense calcium uptake and the root will grow in that direction instead, normally right against the side of the rock, liner or whatever.

It is true the root growing along a liner will increase in diameter and push against the liner. But there is nothing sharp to punch through the liner. To the contrary the shape of roots will take the path of least resistance and the diameter will push out more into the soil. But there is some pushing against the liner. On the other side of the liner is water which moves out of the way. This is no different than the stress the liner already has pushing against the soil. A stress liners are built to handle.

When you take a root bound plant out of a pot you can see the roots turn when they reach the side of the pot. They don't sit there and try to hammer through. Only when extremely root bound does a plastic pot even start to be stressed.

The diameter of roots are largest close to the base of the plant, like a tree. Root diameters get small pretty quickly from there. Tap roots are an exception but they point downward so shouldn't be a concern for liners. So planting a tree right up against a pond will probably not be good long term. Just like planting a tree right next to a sidewalk can cause problems. But the problem will be the mass of roots pushing against the side of the pond. Roots will not punch through the liner. They simply do not possess the ability.

Step 2: Understanding the human mind.

Pick any pond forum...I'm an expert pond builder and I've seen roots punch holes in liners. Here's a photo of a root punched through a liner proving they do.

Point set and match. How do you argue with photographic proof? With science and logic.

I found this photo at Carpvale's web site. They don't say anything much beyond this root was a pond plant. So I'm not picking on them, on the contary posting the picture is a big help to pond keepers. It is interesting this is a picture of a root growing out of a pond rather than a root growing into a pond. Does this mean plants in a pond will punch holes in your liner? Of course not. But what about this picture? Read on.

Our brains are wired to remember horror stories. Boring scientific facts...not so much. Back in the day you only had to hear a story once of someone being killed by a lion to know petting a lion is probably a bad idea. The more scary the story more likely we will believe it. There are people today who actually are afraid of zombies. Google "zombie preppers".

Root storys are pretty scary. Spending $1,000 - $10,000 on a pond only to have a root grow hrough it is enough to drive many people considering a pond away from ever considering it again. And that's a shame. Pond forums scare off many would be pond owners with all kinds of scary myths.

A photo of a root growing through a liner is just that, a root thru a liner. The idea that the root punched thru the liner is only a theory created purely from a person's imagination. If you have no idea how a root grows it's a reasonable guess. Because they can't think of any other reason the imagined cause becomes fact to them. This is such a common logic flaw it even has a name, argument from ignorance.

It would take a bamboo root to dislodge this "fact" from their brain once embedded..Without any kind of understanding these "experts" often become extremely insecure and resort to bullying as their only defense. Because they invented the "fact" they own it and will defend it like a child. On the other hand a person citing published information has no reason to be defensive...it's not their fact. If someone can point them to a better fact they're more than happy to change their mind. Insecurity on the web is very easy to spot.

I think most people would concede roots growing thru liners is not wide spread. The photo above is the only one I could find. I assume there are more, but Google didn't exactly bury me in images either. In my 20+ years of reading and posting in many pond forums I've never seen such a picture. That fits the science which tells us roots don't have the ability. If they actually did have the ability we'd be hearing about the problem 10 times a day in every pond forum. It would be a huge problem. So I think it's reasonable to consider other causes.

Let's consider where roots first got their infamous reputation, way before pond liners were around.

Sewer pipes. Not just any sewer pipe, from clay sewer pipe and even more so from cast iron pipe. I think with the clay pipe people understood clay pipes break easy. But when heavy cast iron pipes were broken and blocked by roots their infamous reputation grew by leaps and bounds. The cause found by plumbers is that roots were entering atnon-water tight joints and cracks from non-root causes. Even the smallest holes in a joint allows root hairs to enter. Once inside the root diameter, the real work horse of roots, grew and pushed apart the pipe. In many cases the house foundation settles on the sewer pipe and will crack a cast iron pipe allowing roots to enter.

If root can't punch a hole in a liner then how can a root growing thru a liner be explained? Well logic would say the hole must have already been there. Is that reasonable? What we know from sewer pipes and roots it seems reasonable to me. Can a hole occur in a liner from a source other than roots? Of course.

This is a picture of a new EPDM liner I purchased that, from the look of it, was dragged across a concrete floor. Pretty common in forums to hear about holes in liners. Tree branch falling into the pond at just the right angle, dog climbing out of a pond, Herons, or a million other ways. Holes in liners are not uncommon..

Is theory of a root growing thru an existing hole more reasomable than the theory of roots punching the hole? From the number of reports in forums I think it is.

A liner installed with a pin hole will generally not be noticed because the water losss is very little. A large hole of course is going to be noticed and fixed before plants get a chance to enter.

Once there is a small hole water will leak out. That may only be a single drop an hour but that's plenty for a root. A root hair will find that hole. To the tiny root hair even a pin hole will be a huge hole. It will grow thru the open space no problem. Then the diameter work horse takes over and pushes outward streching the hole more and more. Might ever cause a rip if the root gets large enough and depending on the kind of liner.

In a funny way a root can seal a liner hole. The root diameter will exapand and strech the liner tight sealing the leak. Same thing happens in potted plants set on the ground. Tap root grows thru the pot's drain hole, increases in diameter until the drain hole is sealed.

What about the deadly bamboo roots?

No different from any other root. There are more myths about bamboo than even with ponds. I'll say this, if you're a gardener and might consider bamboo you owe to yourself to check it out...with people who grow bamboo professionally...not with forum "experters". They're great plants and there is no reason to fear them if you learn just a tiny bit of real information and dump the tons of crap information.

There is one huge downside to bamboo. If you plant it you will have to hear from every "plant expert" that ever sees your garden about how dumb you were to plant bamboo. They will go on and on telling you about one horror story after another even though their entire gardening experience is limited to ordering a salad.. It's like some kind of "plant expert" network. It really can be insufferable.

Conclusion

Science has shown us roots have no way to punch holes in water tight materials like rocks and liners. Not only do they not have the physical ability but they actually have systems to ensure they don't waste resources trying.

The theory that roots grow thru existing holes in liners is more plasuable. It uses the way roots grow. It fits better with very few people say they've seen roots thru a liner.

The theory that the roots themselves punch holes in liner has absolutely no science backed basis. Only imagined "fact"..

Not all liners are equal.

The stronger the liner the more likely it is to hold up to abuse. Shipping abuse, installation abuse, rocks, dogs, kids, gardeners, Herons, you name it. So if you still worry about roots buy a 45 mil EPDM liner. They're tough. To reduce your fears take a sharp stick and do your best to punch a hole thru a piece. It is possible but most people can't. It's tough stuff.



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