The Best Trees to Plant Around Ponds (Non-toxic Native Species)
Incorporating trees around your koi pond is a wonderful way to add a charming, almost enchanting feel to your pond while also providing a host of other benefits. The roots of trees will help prevent bank erosion on and around your pond as well as help to soak up any excess nutrients or pollutants before they have a chance to wreak havoc on your water quality.
In addition, they’ll provide habitat for all sorts of birds and small mammals, aid in shading your pond in the summer, provide food for local wildlife, create a more natural and whimsical pond appearance, and they’re perfect for hanging up a hammock to relax and enjoy your beautiful handiwork!
Koi Pond Tree Planting Considerations
While trees provide many benefits to your pond ecosystem, as well as its overall aesthetic, there are some things that should be taken into account when thinking about planting trees near your pond. You’ll want to avoid any toxic species or families that could harm your fish, such as black walnut (specifically, the husks of walnuts, which contain a toxic chemical called juglone that kills fish once they drop into the water), buckthorn (an invasive species regardless), cherry (or anything in the stonefruit or prunus family), gingko, and many others.
Additionally, while trees will help remove pollutants and any nutrient surpluses from the soil, falling leaves will add waste to the pond. This means more pond maintenance, as you’ll have to fairly regularly clean leaves out of the water to prevent nutrient buildup and excess algae growth as the leaves decompose. Utilizing some form of algaecide with natural, biological micro-organisms will also help to break down decaying leaves that have amassed.
You will also have to keep in mind that after a few years as trees develop, there is potential for roots to pierce your pond liner. To help prevent this, you can purchase a thick (preferably rubber) pond liner, place bricks or clay pieces around the outside of the liner to block the roots, or purchase a extra protective underlay matting.
The Best Native Koi Pond Trees (Pond Tree Suggestions)
1) Willow (Salicaceae salix)
Willows are majestic, unique trees that can really add a very picturesque element to your pond. The salix genus encompasses over 400 species of willow trees and shrubs, so you certainly have a wide variety to choose from! They’re excellent purifiers and bank stabilizers, and thrive in the moist soils near water. Weeping willows are quite a popular choice, with their dramatic, graceful sweeping branches arching over your pond and creating a stunning reflection (the downside here is cleaning up fluffy catkins from your pond), and aren’t overly towering – they reach about 40 feet in height.
Pussy willows are another good choice, as they don’t produce as many catkins as other willows that will blow all over your pond, and they only reach a height of about 15 feet so they’re easy to maintain. However, you should be aware the some willows, particularly the larger trees, can soak up as much as a quarter inch of water per day, so you shouldn’t plant them if you have a small pond or live in an area that’s hot and/or doesn’t get much rainfall. Most willows prefer full to partial sunlight, so having an average of at least 4 hours of sunlight per day is best for them. When they’re young, they’ll need full sun in order to mature so don’t plant them in the shade of any already established mature trees.
2) Juniper (Cupressaceae juniperus)
If you live in an area that requires a more hardy plant (such as a mountainous or dry region), members of the juniper genus/cypress family may be better suited for your koi pond. They’re an easy to maintain group that can easily add some exotic-looking character without actually using an exotic tree (unless it’s a Japanese variety…we’ll talk more about oriental species later in the article).
You can choose between about 60 species, from bonsai or shrub junipers that are smaller (typically less than 5 feet tall) to weeping junipers that will create a similar affect as weeping willows but on a much smaller scale (about 15 to 20 feet tall as opposed to 40), or a multitude of species of trees ranging from 15 to 130 feet tall. In addition, you won’t have to deal with any fluffy catkins getting everywhere – junipers reproduce via small, attractive blue-ish berries on the female portions of the plant that can be picked and used in spices, jams, and baking, while the male portions of the plant produce very small cone-like structures.
Junipers in general are attractive, fragrant plants, and are also evergreen, meaning that they will keep their leaves and gorgeous blue-green color (and thus continue to beautify your pond landscape) throughout even harsh winters or extremely dry summers (they are, after all, adapted to arid mountainous environments). The berries can also be munched on by your fish if they fall into the water, and the dense branches will attract many songbirds for cover and shelter.
3) Red Maple (Sapindaceae acer rubrum)
Many with koi ponds opt for Japanese maples for a more oriental look, but red maples are native and still quite striking. With vibrant green leaves in the spring and summer that turn a dazzling array of reds, oranges, pinks, purples, and yellows in the fall with bright red petioles to contrast the leaves, red maples are a sight to behold throughout much of the year.
They do best in moist soils, meaning that they’re perfect for planting near water. In addition, they’re quite hardy and widespread, able to grow in hardiness zones as low as 3 and as high as 10, surviving both frigid winters and brutally hot summers so long as they have access to water. They’re also among some of the first trees to leaf out in the springtime, so you can typically enjoy them from March or April through late October or early November, depending on your hardiness zone. The more temperate the region, the longer they will hold onto their leaves. Maples reproduce via seed structures called schizocarps (many people refer to them fondly as “helicopters”), so you may have to clean these from your pond from time to time in late spring and early summer. They’re fairly fast growing, reaching maturity in only a decade or two, with an average height of 60 to 90 feet. You may have to trim the branches every now and then, especially if you plant it quite close to your pond.
4) Dogwood (Cornaceae cornus)
Another native tree in many regions of North America, dogwoods produce gorgeous flowers of varying sizes and shapes that provide a wonderful accent to most any koi pond. This family encompasses 30 to 60 species (depending on who you ask – some botanists identify and group them differently), and includes both trees and shrubs.
Considered to be a relatively small tree (growing to around 20 to 40 feet tall, depending upon the exact species), dogwoods flower early in the spring and throughout part of summer. Flowering dogwood is the species most commonly envisioned when dogwoods are mentioned – with large, showy flowers (technically called bracts) that are typically white, pink, or red, and leaves that turn a striking scarlet red in the autumn. Some claim the berries to be marginally poisonous to koi, but there haven’t been any actual documented cases of illness or death, or of the fish finding the berries to be palatable and eating them. Many pond owners have attested to having dogwoods around their ponds with no sign of harm to fish. Just to be safe, however, plant the tree several meters away from your pond to lessen the likelihood of berries falling into your pond, as well as curtailing too many leaves from dropping into the water. Chances are that birds will eat most of the berries anyway, as they find them to be quite tasty.
5) Magnolia (Magnoliaceae magnolia)
The magnolia family encompasses about 35 species comprised of both trees and shrubs, with 5 of them native to the United States. They range in size from shrubs of 10 to 15 feet tall to large trees over 70 feet tall (magnolia grandiflora, or southern magnolia). Though some varieties do just fine in northern climes (even as far north as New York), magnolias are generally adapted to warm, damp climates – making them a perfect choice if you live in such an area, and their proclivity to moisture means that they do quite well near ponds, rivers, and the like. Magnolias are well known for their elegant, large beautiful flowers that can be white, pink, yellow, purple, or any combination thereof. These flowers bloom before the leaves bud out, making these plants especially eye-catching in the spring when most other vegetation is still barren. Their leaves are fairly large, thick, waxy, and a deep, tropical-like green color. Overall, these trees require very little care once established.
What About Oriental or Exotic Trees?
While oriental species, such as crepe myrtle, Japanese maple, and Japanese willow, all look attractive and are often highly sought after for placement around koi ponds, they are not native to the U.S. or Europe. Any exotic species has the potential to spread and overtake natural environments, or to hybridize with native species via bees, wind, and other forms of pollination. In many areas, these exotic species are considered to have “escaped cultivation,” and as such are growing in natural areas where they are able to out-compete native species that haven’t evolved with the invasive and therefore don’t know how to compete with it for space and resources. Because of that, it is very easy for exotic species to overtake large areas, thus vastly decreasing biodiversity and decimating entire ecosystems.
It is always recommended to plant only native species that are adapted to your area and thus won’t endanger the surrounding ecosystems. As showcased above, there are a variety of native tree and shrub species that can still lend an exotic feel to your pond without damaging any of your other plants or the surrounding natural environment. With that being said, if you must include species that aren’t native in order to obtain your desired aesthetic, some species are not considered invasive (with invasive meaning that they are known to spread pervasively), and are just considered non-native (which still isn’t necessarily a good thing, but also not always bad). Among those considered simply as non-native alternatives to invasives are Japanese snowbell, trident maple, and tall stewartia.