Preventing Browse Damage to Planted Tree Seedlings

Photo: Ken Bevis/DNR.
Photo: Ken Bevis/DNR.

It’s tough being a critter out there. Food, water, cover and adequate space are all that wildlife need. But sometimes, our trees become essential habitat elements, too. Wildlife’s quest to survive may, at times, place them at odds with our objectives of growing trees, such as when carefully planted seedlings are mutilated or simply eaten by feeding deer and elk. Fortunately, there are steps you can take to prevent or, at least, contain the damage.

First, determine if there really is a problem. Usually damage is noticed on some trees during forest walks, but this doesn’t give us a real sense of scale. It is important to objectively assess the situation to determine a proper course of action.

Note what kind of damage is occurring: Are the buds and/or foliage damaged or eaten? Are there chew marks and nipped buds? Are the stems torn or cleanly nipped? Is there girdling? Was the stem damaged by physical rubbing? How high is the damage? What kind of marks? Deer and elk will tear the top out of seedlings, or pull them out of the ground.

Second, note the extent of the damage? How many trees are damaged or dead? What tree species are affected? What proportion and spacing of the trees are affected? Informal tree counts or even plots can give a better assessment of what is going on. Several simple methods work to give some numbers: Count 100 random trees on narrow transect (say 6-10 feet per side) and keep a tally of the number damaged. Another method could involve some circular plots (1/20 acre or 37.2 feet radius is good) and again, count. Count the number of target seedlings or saplings, both intact and damaged, to get an estimate of damage. Otherwise, our eye is very biased and will overestimate damage levels by focusing on the damaged trees. This is an important step.

Seedlings and deer

a tell-tale sign of deer damage.
The ragged edge where this seedling’s top was nipped off is a tell-tale sign of deer damage. Photo: Ken Bevis/DNR.

One of the most common animal damage complaints in forestry is seedling destruction by ungulates. Deer, and elk, will browse many different kinds of vegetation as they saunter across their home ranges. They will sample any number of plants as they feed, stopping to focus on those they particularly like. They will often eat the tops out of planted tree stock, particularly cedars. Deer and elk have no incisor teeth on the top of their mouth, so they roughly tear the vegetation. (Hares will cleanly nip at an angle.) Nursery stock seem to be particularly yummy, and can be selected like ice cream in newly planted areas. Other species of trees can also have their tops nipped out, killing or causing odd bushy growth in those trees that survive. How can you prevent this damage from severely reducing the success of tree plantings? Read on…

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There are five basic approaches to preventing or reducing wildlife damage:

  • Tolerance – in other words, putting up with it and planting extra trees
  • Armoring with Vexar(R), cages, tubes, bud caps
  • Repellents
  • Alternative food sources
  • Removal or harassment

Tolerance: In any damage situation, first determine if the level is acceptable. For example, if browse damage is expected, simply plant at a higher density and allow for some loss. This could mean additional thinning in the future, but protection is not necessary. Ask yourself, are the animals engaged in early thinning? The best wildlife habitats are structurally heterogeneous, with openings and shrubs mixed with mature trees anyway. Animal damage can actually create some of this diversity! Is the damage within acceptable levels? If so, there is no “problem”!

 flexible plastic mesh tubing, such as Vexar®, around seedling
Placing flexible plastic mesh tubing, such as Vexar®, around seedlings can be an effective way to prevent damage by deer and other wildlife

Armoring: If they can’t reach it, they can’t eat it. Placing a cage of some kind on each tree, is an effective option. The goal is to get the tree large enough that if a deer or elk decides to eat it, the tree will survive and the top will remain intact. Vexar® tubes (photo) or other plastic tubing, is commonly used and can be very effective. This method is labor intensive but small woodland owners can make good use of these tubes. These manufactured tubes can be secured with one stake, zip ties or wire, and moved upwards as the tree grows.

Thin bamboo stakes held together with zip ties work well. Home-made cages also work, using wire of various kinds. Two-inch rolled steel mesh, 4-feet high, secured with a T-post is standard on many restoration plantings in north central Washington.

Famed tree farmer, Ron Munro at the Crystal Lake Tree Farm near Monroe, Washington has had good results tending his Western red cedar seedlings by installing Vexar® tubes and lifting them as the trees grow.

Be sure the stakes are strong enough to withstand snow or other local environmental factors. Usually the deer will nose around and move on to the next plant if there is a barrier. Remember, the barrier has to be stout enough and tight enough to prevent deer noses from getting in. Elk are big and strong, and have been known to pull cages off when they really want to eat something. In wetter environments, some have planted a spruce immediately alongside cedar, and the deer will sometimes leave the cedar alone; maybe because they don’t like to bite the spiny spruce!

Bud caps are paper or plastic envelopes stapled over the terminal bud of seedlings. Sometimes this can be very effective at preventing key damage. The covers need to be checked and fixed annually however.

Repellents can be an effective alternative, but must be reapplied regularly for consistent results. This often means, twice, or more, per year. There are many products responding to this need, with at least 20 on the market. Two commercial products that have good track records are Seadust and Plantskydd, both manufactured with forestry in mind, with a foul taste that the browsers just don’t like. Look in hardware stores in areas where deer frequently eat ornamentals and the number of repellents on the shelf can be amazing! Experiment and ask around in your local area to find out what works.

Alternative forage: Another technique to reduce big game damage to seedlings is to provide a preferred alternate food source nearby. An Oregon experiment placed preferred forage near planted stock, and found this technique reduced damage to planted seedlings. This could be done in the form of planting wildlife forage mix in food plots, on skid trails and disturbed soils.

Removal of offending animals is a tactic of last resort. Usually, the wildlife populations will simply fill back in behind the best intended efforts. Legal hunting can be used to remove some animals, and will produce effective harassment, but only during periods of hunting. And hunting must be carefully tended to avoid conflicts with neighbors. Seldom will hunting remove enough animals to eliminate damage. Harassment (motion-operated sprinklers, dogs, noise) can teach animals to stay away from certain areas, but these techniques are labor intensive, require constant vigilance, and often must be used at night. In any case, most wildlife quickly learn to ignore your most obnoxious efforts. Consult with your local fish and wildlife departments before embarking on programs involving ANY removal method to be sure you are acting within legal limits.

Enjoying wildlife on our small woodlands is one of the great joys of forestry. When they damage our trees we must carefully consider all of our options for dealing with the situation.

If you have questions about wildlife on your small woodlands, please contact me:

by Ken Bevis, Landowner Assistance Wildlife Biologist, Washington State Department of Natural Resources, Ken.Bevis@dnr.wa.gov, 360-489-4802