Willow trees can be a great addition to your yard if you have the space, and they sure look nice next to a big natural pond, but I thought I should give you a bit of a warning about these fast-growing trees and your smaller lined ponds.
People often say that willow trees will suck up a bunch of water, which is probably true. They do seem to be very thirsty trees. I have come across several instances where Willow tree roots have entered a pond and caused quite a bit of extra work and hardship for the pond owners.
In both cases, the Willow trees were probably ten feet from the pond edge, and in both cases, the roots went up and over the pond liner. Once the roots got a taste of that fresh pond water, they were hooked, and they just kept growing and growing and filling up the space.
Now don’t get me wrong, I’m sure the willow roots were taking in a bunch of nutrients, and I’m sure that they were helping to keep the pondwater free of algae, but inside a lined pond, they just tend to take up too much space. They can plug up pump intakes and fill up the pond bottom.
One of the ponds was a small skimmer box pond, and the roots were quite established. Check out the pics below. We had to move most of the pond rocks, pry the roots off the pond bottom and cut them out beyond the liner. The roots didn’t pierce the liner, so once they were removed, we were able to finish up the pond cleaning and put everything back together. We reclaimed at least a foot of pond depth by removing those nasty roots.
The other pond had a wet well intake, and the Willow tree was on the intake side of the pond, so the roots crawled down into the intake. They weren’t nearly as large as the roots in the first pond, but they were deep into the wet well intake, so we needed to remove many rocks and quite a bit of gravel to get them all out. Once we had them cleared out, we installed a thick polyethylene root barrier and left it standing tall an inch or two out of the ground so that the roots would need to go up into the open air in order to get back down into the water. We hope this will prevent this from happening again, but we will keep our eyes on it to be sure.
If you have a willow tree or trees in your yard that are anywhere near your pond, I would suggest checking the pond edge to ensure the roots aren’t getting in. One relatively simple fix to this problem would be to dig a trench, cutting the roots somewhere near the pond edge. Once you have a trench, you might as well install a poly root barrier. This should at least slow the roots down and make it easy for you to see if they are trying to creep in.
Don’t get me wrong; I am not against the willow tree, I really love their look and their fast growth. If they are near a natural bottomed pond, the roots will surely be in the pond, but if the pond is large enough, they aren’t likely to do any damage; they will simply soak up water and take in a bunch of nutrients. But, if I were you, I’d make sure to keep them out of my lined pond.