City of Minnetonka

Debunking natural resources legends

Tree roots grow down like a carrot

While it’s true that certain species like oaks have a tap root when they are small saplings, the roots of established trees have a shape more like a wine glass. In fact, the majority of all tree roots are within the first three feet of soil, with most fine roots within the first foot of soil where oxygen exists. Trees have a root system that extends outward below ground at least as wide, and sometimes two to three times as wide, as the canopy above. Remember this and use caution when you are disturbing soil or driving heavy machinery under a tree’s canopy—it’s called the “drip line” of the tree and its preservation is crucial to the tree’s survival.

Mature trees don’t need to be watered

Mature trees are just as susceptible to drought damage as young trees, especially if they are growing in a landscape without a layer of organic material to conserve soil moisture. In a typical lawn setting, trees endure chronic low-level stress. This occurs because soil has often been compacted—instead of tiny spaces in the soil for roots to grow through, root movement is restricted, making water uptake more difficult for the tree. When the situation is compounded by a drought, the soil becomes so dry that the fine roots of the tree also dry out and die. Fewer roots underground mean the tree has a decreased ability to support the aboveground portion of the tree. A mature tree already has a difficult time supporting itself because as the size of the tree increases, the relative proportion of “sugar making” tissue to non-sugar making tissues decreases. In order to maintain tree vigor, plan to water your mature tree with a drip watering hose or a hose on low flow, moving it around to the outer edges of the canopy.

Garlic mustard is not a problem on my property. I’ve only got a few plants.

A few garlic mustard plants can multiply exponentially and take over the herbaceous layer in shady woods and gardens in only a few years. Garlic mustard is a big problem in Minnetonka woods and natural areas. The best time to remove it is now! For more information on this very invasive European herb, its life cycle, and how to control it, visit eminnetonka.com.

Earthworms are good for the soil

Earthworms are good fish bait and robin food. They’re okay in your garden and lawn, but they are harmful to hardwood forest habitats throughout Minnesota. Nearly all of the terrestrial earthworms in Minnesota are non-native, invasive species from Europe and Asia. Earthworms cause harm to the woodland ecosystem by consuming the duff layer in the forest, which is essential for the survival of many species of wildflowers. Prevent their spread to new areas—don’t dump fishing bait in the woods!

Low-maintenance landscape means no maintenance

Native plants have been touted for years as being low-maintenance; and this is true, once they are established! When new plants are small or getting established, there’s always competition for light and moisture by volunteer invasive plants and weeds. If you take the time to weed, mulch, and water around new plantings during the first few years, the annual work required will surely become low maintenance.

If you cut buckthorn, it goes away

This could have been true 25 years ago if the fresh-cut stumps were carefully treated with the proper herbicide. Today, buckthorn has been around in most local woods for 15 to 45 years. Buckthorn can produce fruit with seeds as early as six years after germination, which means the seed bank in the soil has been building for many years. As the female trees grow larger, their annual fruit production grows exponentially. Buckthorn seeds remain viable in the soil for years; so now, when buckthorn is cut and the stumps are properly treated, thousands of seeds can germinate in the subsequent seasons. The trick to continued control after the larger buckthorn has been cut is to pull seedlings when the soil is moist, pull, replace the soil, be careful of the remnant native plants, mulch, and repeat for many years into the future! Visit eminnetonka.com for more information on buckthorn.

I have poison oak on my property

That’s not likely in Minnesota, since poison oak isn’t native here. It grows in east coast states and southern states in the Texas/Louisiana/Arkansas region. We do have plenty of poison ivy in Minnesota. Poison oak and poison ivy are two woody perennial plants that are very closely related. They both have compound leaves-of-three and a “poison” oil called urushiol which causes an itching and blistering dermatitis on humans. Wildlife eats the plant and beds with the plant with no ill effects. As its name suggests, poison oak leaves can look much like the leaves of white oak while poison ivy can be a little harder to identify. Until you learn the key identifying characteristics and the many sizes and forms poison ivy takes, the best advice is: “leaves-of-three, let-it-be.”

I don’t need to worry about runoff or water quality because I don’t have a wetland, creek or lake on my property

We all effectively live on waterfront property. The runoff from your property will drain into the nearest lake, wetland, or creek even if you do not live directly on the water. Runoff that exits your property will carry with it any fertilizers, herbicides, oils, sediment, pet waste, yard waste, or any other material that can be dissolved or floated in the water. In addition, this runoff can pick up additional materials such as loose gravel, spilled chemicals, litter, or any other items it encounters on the way. Although we all contribute to the potential problems that affect our water resources, we also can contribute to the solutions. Keep paved surfaces clean, cover exposed soil, and use techniques to capture and absorb runoff such as planting or protecting areas of native vegetation, installing rain barrels and rain gardens, and preventing soil compaction during construction and landscaping projects.

The water in the storm drain is “treated” like the water from my home

Storm drains capture water from roadways or depressions in the landscape to keep streets safe for travel and to help prevent the flooding of nearby homes and businesses. Once the water enters the storm sewer system, it’s directed underground by large pipes or culverts to a nearby lake, creek, or wetland. Some storm sewers may release this water into a drainage pond first to help control the speed or volume of the water; however, this water will eventually pass into the lake, creek, or wetland once it rises to a certain elevation. Unlike the sanitary sewer connected to your home, water that enters the storm drain is not treated at a wastewater treatment facility. Consider adopting the storm drain on your street and periodically disposing of any leaves, twigs, litter, or other debris that you find collected around the storm grate. Throw out that debris with your trash or yard waste—don’t push it down the storm grate!

Non-phosphorus fertilizers are harmless to water resources

It’s true that excess phosphorus can increase the presence of algal blooms that reduce water clarity, and can have other negative impacts such as an increase in the growth of exotic weed species. Minnesota banned the use of fertilizers containing phosphorus for established lawns largely due to the existing abundance of phosphorus in our soils and the impacts of phosphorus on water quality. Other nutrients in fertilizers, such as nitrogen, can encourage the growth of algae and noxious weeds, especially if phosphorus is already abundant in the water. Also, fertilizers may contain herbicides that kill vegetation. Always read the labels carefully and have a soil test before applying any fertilizer, including organic fertilizers, to your lawn. Use slow release fertilizers on areas where the potential for water contamination is high, such as sandy soils, steep slopes, and compacted soils.

My trees are too close together

In a woodland environment, trees often will grow much closer together than if they had been planted in a yard. However, these trees have grown from seeds or sprouts and have adapted to the trees and shrubs growing around them as the woodland was formed. The overall health of your native woodland will not be improved by “thinning out” the native species. Instead, you may harm the remaining trees. Removing tall trees from the canopy or small trees from the understory may expose the soil below to the direct impacts of rain, increasing the potential for erosion. Removing the native understory also may provide an opportunity for buckthorn, a non-native invasive species, to become established. Heavy equipment used for tree removal may compact the woodland soils or wound the surrounding trees, potentially stressing and impairing their health. Most species will not form major branches along the trunk of the tree once they have developed; thus, you should not expect trees that have grown in a woodland setting to form a new, more rounded canopy once the surrounding trees are removed. If you have remnant trees from a native woodland in your yard, remember that it may have taken hundreds of years for this woodland to develop. Protecting it is the easiest and often least costly way to enjoy its beauty for years to come.

Questions or concerns?
Ask Minnetonka Mike!