Zombie Trees: OK on Outside, Dying on Inside

It sounds ominous. However, Jason Grabosky, professor of urban forestry in the Department of Ecology, Evolution, and Natural Resources at Rutgers University’s School of Environmental and Biological Sciences, says there’s no cause for alarm. Zombie trees shouldn’t scare you.

Yes, a zombie tree that appears to be rooted in the ground can topple over and crash on top of your car, garage, house, or even passersby. The likelihood of that happening is small — especially if you pay attention.

What Are Zombie Trees?

Zombie trees are dead trees on the inside. On the outside, they can look like a perfectly healthy tree. These dead trees can flower and produce full foliage in the spring. Some dying trees, much like the zombies in “The Walking Dead,” have patches of bark (or skin in the case of an actual zombie) peeling off. They can be found all over the country from New Jersey to Oregon.

How to Tell if a Tree is Dying

Not all sick trees are obvious, and different tree species will show different symptoms. Here’s what you should look for:

  • Hanging limbs.
  • Deadwood, decay, or fungus on the tree.
  • Dieback of the crown (common on trees suffering drought stress).
  • Split trunks.
  • Cracks and/or deep splits through the bark in the trunk or limbs.
  • Discolored leaves and leaves with dying tips.
  • Prematurely falling leaves on a mature tree.
  • Leaning toward one side or branches growing out of proportion.
  • Cracks in the soil and other root problems.
  • Insect infestations such as bark beetles.

What Causes Dead Trees?

Professor Jason Grabosky
Professor Jason Grabosky

“Trees grow and as they age, they have something in the center called heartwood,” Grabosky says. “Heartwood is the dead inner wood and there’s sapwood, which is the living outermost portion of the tree.”

A tree dying is natural. They don’t live forever. With proper care, though, they can last a long time. The main causes of tree death are insect infestations, fungal disease, and climate change (excessive heat, droughts, too much rain, and hurricanes).

“It’s also important to check the soil near the base of the tree,” Grabosky says. “Often problems start because of damage to the soil. A healthy tree’s roots need air. Heavily packed soil surrounding the tree harms the tree. And you don’t want heavy equipment on top of the tree’s roots. Without pockets of air around the roots, you’re compromising the tree.”

Another way to tell if the soil in your yard and around your trees is healthy is to look closely at any weeds growing nearby. The different weeds that crop up in your yard can provide clues such as if the soil’s too acidic, waterlogged, or dry.

“And mulch is better than grass around trees,” Grabosky adds.  Mulching can reduce weeds and help the soil accumulate more needed nutrients such as nitrogen, phosphorus, and potassium.

What About Shrubs and Bushes?

Shrubs and bushes can also become undead. You can tell by looking at the dry, brown, and brittle leaves on the branches. If you notice any green foliage, you may be in luck. That part of the plant is alive. To fix this, start pruning the dead parts off the plant.

For barren branches, take your fingernail and gently scrape away a bit of the outer layer. If you see any green underneath, your plant is alive. The same goes for the trunk of shrubberies. If you see a bit of green underneath after scraping the bark, your shrub is alive.

It’s important to note the time of the year, too. Some bushes and shrubs can become dormant in the winter and summer months.

How to Save a Dying Tree

Dying trees can be turned into healthy trees. It’s possible, with careful tree care. “I’ve seen trees in decline rebound from infestations,” Grabosky says. “A lot depends on the species of tree and how much damage has been done.”

If it is an insect infestation, like cankerworms, pine beetles, wood borer or bark beetles, and you catch it early, you can transform a near dying tree into a healthy tree.

First, identify the problem. If it’s fungal, an insect infestation, or a climate problem such as the result from drought or hurricane, you’ll want to call a certified arborist or licensed tree expert. A professional arborist or licensed tree expert will come out and evaluate the situation.

To transform a dying tree into a healthy one try:

  • Checking how much water you are giving your trees. Too much or too little can harm the tree.
  • Prune your tree or have an expert do it.
  • Use fertilizer.
  • Cover the surrounding area with mulch.

Tree Removal

“Climbing up on ladders with power tools can be dangerous if you don’t know what you’re doing,” Grabosky says. “Hire a professional to remove your dying tree. And depending on where the tree is located, you might want to leave it where it is.”

Some dead trees placed away from houses and roads won’t cause any damage if they fall and they provide homes to animals. “A biologically dead tree is just fine,” Grabosky says. “We need these habitats for a healthy ecosystem. Remember, just because it’s dead doesn’t mean it’s dangerous.”

Michele C. Hollow

Michele C. Hollow