At the Side of Spring Creek: Weeds Around Tree Shelters

If you have had the pleasure of planting a vegetable or flower garden at home, you know that shortly after you finish prepping the soil and planting your desired vegetation that all sorts of uninvited plants start growing there too. These undesirable plants, often called weeds, and can pose a huge problem for the plants that you intended to grow. This same issue often occurs after planting a riparian buffer, and our new buffer along Spring Creek in Dauphin County, PA is no different.

So, what’s wrong with weeds? Well, besides them being undesirable and unattractive, some of them can also be invasive. Invasive weeds are those plants that did not historically grow wherever you are, in this case here in Pennsylvania, and that have an impact on the environment that they are introduced to. These plants come from other regions and other countries and were often introduced by accident. Weeds may also pose a significant hazard to public health, property, or economic income. Those weeds are called noxious weeds, and the Pennsylvania Department of Agriculture has an updated noxious weeds list that identifies them. Many of these weeds, including Mile-a-Minute, Multiflora Rose, Japanese Knotweed, and Wild Parsnip, are very commonly found on riparian buffers. All noxious weeds should be managed in an effort to remove them from a site once you identify them.

The main concern with weeds in a riparian buffer is the direct competition they can become for your newly planted native trees. Weeds often outcompete recently planted trees for both above- and below-ground resources such as sunlight, available water, and nutrients. These undesirable plants often win the fight since they grow roots and shoots much faster than the native trees. Competition can be especially fierce during time when there is limited water availability. Often, weeds left unchecked will end up in dead trees that you will need to replant, costing you more money and extending the time it takes to get your buffer established with mature trees.

This photo shows a direct comparison of a Mile-A-Minute stem to a newly planted tree trunk. The Mile-A-Minute stem is multiple times larger than the tree trunk. This visually shows the fast-growing nature of weeds and how effective they are in competing for both above and below ground resources. Photo: Tyler Groh, Penn State

So, what can be done? Just like any garden, riparian buffer plantings need to be weeded. There are many methods used to remove unwanted plants and prevent them from coming back. It is always a good idea to mow any non-woody weeds before they go to seed, to prevent them from reproducing. Mowing is a great weed suppressant strategy for between rows of trees in your buffer. In addition to mowing, it is also beneficial to reduce the density of weeds directly around the trees and their shelters. One way of doing this is by spraying herbicide in a 3-foot radius from each tree shelter as seen below. The herbicide used should always be applied according to its label. For our buffer, we used both a pre- and post-emergent herbicide that controls herbaceous vegetation. It is also important to remember that this is sprayed directly around woody vegetation, and herbicide used to control woody plants should be avoided.

A-The 3-foot diameter herbicide spraying radius is still visible months after treatment. There are no weeds outside of the tree tube within this zone to directly compete with the newly planted tree. However, please note the grass and weeds sticking out the top of the tree tube. These must be removed. B-Once the tree tube is off, it is very easy to see just how dense weeds can get within the tree tube itself. It is very difficult to see the tree that was planted. C-Once the weeds are removed via hand trimming, you can once again see the young tree that was planted. D-Once satisfied with the weeding, the tree tube was put into place again to protect the tree from wildlife. Photos: Tyler Groh, Penn State

When tree tube style shelters are used to protect young trees during establishment, these tubes can help protect the trees from any herbicide drift that may occur while spraying. The drawback is that weeds within the tree tube are also protected and can grow within the tubes, potentially outcompeting the young tree. It is a good practice to walk through your young buffer and perform tree shelter checks that involve looking down the tree tube, assessing weed growth, and removing any weeds that may be growing up and around your planted trees. You can remove the weeds by cutting them at ground level with a sharp scissors or a small pruning shears. Please try to avoid pulling any weeds that are closest to your planted trees out by hand since you may also disturb and pull out the tree’s roots too. Any root damage to young trees can be severe and lead to tree mortality.

Buffer maintenance is a labor of love, but you are not in it alone. Thankfully there are great resources available that can help you with this process such as the Growing Great Buffers short video series. Now, let’s go out there and fight the good fight against these weeds.