Healthy Trees

7 Tips for Keeping Your Trees Healthy

Plant the right tree – This isn’t obviously always possible, especially when you have purchased a home that is over 5 years old. But when you do have a choice, choose a species that is well adapted to your climate and the specific conditions of soil, light and space at the planting site. Proper tree care begins with selecting the right tree and planting it in the right place. Try out this What Tree to Plant Wizard from I love this site, lots of great info on trees plus you can get 10 trees mailed to you along with some other cool stuff with a membership donation as low as $10.

Remove stakes early – A tree that is allowed to sway in the wind develops a stronger trunk. Remove the stakes as soon as the tree can stand alone, hopefully after one year.

Keep the grass away and mulch – For best results, maintain a grass-free, mulched area around the trunk. Grass and weeds will compete for water and nutrients and your tree will have restricted growth right out of the gate. Mulch cools the soil, conserves moisture, improves soil texture and reduces weeds. Replenish often. But when placing mulch, don’t pile it around the trunk!!!!

Water and fertilize when needed – Young trees need regular watering, but even mature trees need to be watered during periods of drought. Feed only if trees are growing poorly or have yellowing foliage. A soil test will confirm exactly which nutrients are needed.

Prune correctly – The primary goals of tree pruning are to improve plant health and direct the growth of the tree. You may also need to fit a tree into a specific area, or prune to encourage fruit production.

Protect roots and trunk – Whenever possible, avoid driving cars over tree roots to avoid damage and compressing soil. Consult an expert before changing grade, adding new building structures or doing any major landscaping or digging. Bumping into trees with lawn mowers or whipping the trunks with weed-eaters damages the bark and trunk, weakening the tree structurally while inviting insects and disease.

Control pests and watch for diseases – According to the Minnesota Realtors Association, when a tree becomes diseased, it’s a hazard to the property. Diseased trees are more likely to drop branches than healthy ones, and if the tree covers any part of the home in question, the risk of damage to the roof or other parts of the structure increases. And of course, the larger the tree, the greater the risk—both to the inhabitants and the property itself.

Oak Wilt – Every species of oak tree in Minnesota is susceptible to Oak Wilt. This disease, caused by an invasive fungus, will eventually kill the infected tree. Some of the tell-tale signs of a tree infected by oak wilt are:

  • Discoloration of leaves, around the edges in particular
  • Total drop of leaves by midsummer
  • Dying upper portions of the tree
  • The onset of “suckers”—branches growing from the tree’s base

Healthy oak trees are beautiful, and properties with them are sought after for good reason. But a diseased oak tree can be a major liability, so recognizing the infection will help you advise your clients accordingly.

Dutch Elm Disease – Another fungi-related infection is Dutch Elm disease (DED). It most commonly occurs in American elm, Red elm, and Rock elm trees. As with Oak Wilt, this disease causes an infected tree to die. However, if caught early, the affected areas can be pruned, and the tree can be saved. Signs of Dutch Elm disease include:

  • Out of season yellowing/browning of outer leaves, eventually spreading towards trunk
  • Late spring/early summer drop of leaves
  • Brown streaking underneath bark of infected branches

As noted above, some Elm trees can be treated with fungicides to prevent trees from DED-related death.

Emerald Ash Borer – Perhaps one of the most insidious pests, the Emerald Ash Borer (EAB) is an invasive insect that is hard to detect until it’s too late. If left unchecked, EABs will kill trees they infest. EABs are beetles that affect ash trees. Signs of EABs on a tree are difficult to spot, making this a tough one for any Realtor® or homeowner. Here are a few things that may indicate their presence:

  • Excessive woodpeckers on a tree
  • Spotting the actual beetle —which has a metallic green color—on a tree, (not always easy to do, but it’s possible)
  • Thinning and yellowing leaves
  • D-shaped holes in the bark

If you suspect a tree has been invaded by the Emerald Ash Borer, it’s advisable to call an arborist. They can assess the tree and provide expert analysis and recommendations.

Anthracnose – Another common disease to trees native to Minnesota is anthracnose. This fungus can infect several species of Minnesota trees, but most commonly infects oak, ash, and maple trees. Signs of anthracnose include:

  • Curling/darkening edges of leaves
  • Early leaf drop

Here’s some good news: anthracnose does not result in the death of the tree. Therefore, the risk of a tree falling or causing other damage to a property is extremely low. Nonetheless, given how common anthracnose is, Realtors® and homeowners should be aware of this disease. Recommended treatment includes pruning diseased branches and raking up fallen, diseased leaves soon after dropping.

Apple Scab – The most common disease affecting apple and crabapple trees in Minnesota is apple scab. If you’ve been to an apple orchard in the fall, you’ve likely encountered trees infected with apple scab. Signs are usually easy to spot, and include:

  • Olive green spots visible on leaves
  • Apples that have black lesions and/or brown spots

In most cases, fungicides can treat a tree with apple scab. Proper timing of treatment is important, so it’s helpful to consult an arborist.

Online Resources

Minnesota Tree Identification Guide – U of M

Beginner’s Guide to MN Trees – U of M

How to Plant Trees A Pocket Guide – MN DRN

What Tree to Plant Wizard –


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