5 Trees to Keep Away from Your Water Garden and Why

Posted by Bill Hoffman on Aug 31st 2021

5 Trees to Keep Away from Your Water Garden and Why

Although some of these plants are very attractive and have a reputation for growing near a natural earth bottom pond, it does not mean that they will do you any favors being planted close to the edge of your water garden.


  1. Birch Trees are beautiful trees in a landscape. They are ever so popular for “up-lighting” and as suggested by their name, “River Birch,” are commonly found near bodies of water. Which only makes sense if you are wanting to naturalize the look of your koi pond.

    As an ornamental pond owner, however, a birch tree near your water garden may cause you more pain than pleasure. These trees shed like crazy - all season long! Small branches, sticks and pieces of papery bark litter the ground all around these trees. All this debris in your pond water will add to the ever-on-going battle with string algae. Deep into the summer, especially in NE Ohio, we have experienced drought. This will cause the leaves of the birch tree to fall prematurely, adding to the mess in your pond water.

    Then there are the roots. These trees are so fond of water that their roots will seek out any trace of water that they can find. Sometimes they will grow over the liner, and sometimes they will find any potential leak and invade that space.

    In the pictures, you can see that the roots of the birch tree planted behind the waterfall are “hugging” the falls box. This was due to a slow leak that was assumed to be evaporation.

  2. Willows are found in tree form as well as shrub form, but which ever variety you seek, you’d be well advised not to put it too close to your pond.

    Just like the birch trees, willows thrive near the water. The roots of a willow tree (or shrub) grow very shallow and can easily venture their way over the edge of the liner and start sipping on the nice cool pond water as they please. As roots begin to grow larger, from all of the glorious nutrients in your pond, they begin to push the liner down. This can create a leak that can easily be mistaken for evaporation due to the slow rate in which it happens. Another thing to watch out for, is that anywhere a willow branch touches the water, it is likely to sprout roots and start another plant. 

    You can see some thirsty willow roots in the pictures above.

    Willows are deciduous, which means they drop their leaves for the winter. The tiny leaves on these plants quickly clog the skimmer filter in the fall causing, sometimes daily maintenance.


  3. Pines grow shallow roots that are arguably as aggressive as the willow and the birch. A pine tree’s roots can extend away from the tree at a distance as much as twice the height of the tree, again threatening growth over the liner. 

    My bigger concern, however, is its needles. Pine needles drop from the tree all year long. It seems like all you have to do is lightly brush by it and suddenly the water is covered with needles. 

    Pond nets cannot seem to keep them out of the water, and the skimmer has a difficult time preventing them from reaching the pump intake. 

    As if that wasn’t concern enough, pine needles are very acidic (pH 3.2-3.8). Although throughout the process of decomposition, microbes may neutralize them, a consistent buildup of pine needles in your pond water may lower the pH to dangerous levels for your koi and other pond fish.


  4. Cherry Trees drop leaves into the water, which of course, adds to the fight against algae control and keeping the skimmer clean - but the fruit and seeds (pits) are the real problem. 

    The pits or seeds from plants in the Prunus genus (like apricots, cherries, peaches and plums) contain a form of hydrogen cyanide, also known as prussic acid. 

    Consuming just one or two cherry pits could cause death in your beloved pond fish.




  5. Black Walnuts are very particular about the company they keep. There are many plants that are not able to tolerate the toxins produced by all portions of the black walnut tree (except the nut itself). The substance called juglone is spread through the ground via the roots of the tree, keeping some sensitive landscape plants from growing within the proximity. 

    In addition to the mess of nuts that it drops, the hulls on those nuts become toxic as they begin to decompose. The particular mold that starts the decomposition on the hulls of a black walnut releases a neurotoxin which is toxic to livestock and can be fatal to dogs and fish.

These are not the only plants that can cause trouble for your pond fish and water garden, but they are the ones that we have seen the most problems with. In need of pond netting, pond water test kits, or other pond accessories? Shop pond supplies online right here at waterxscapes.com.