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Tim Boland in Missouri with a baldcypress, or Taxodium distichum, which also grows at Polly Hill Arboretum in West Tisbury, where he’s executive director.

Courtesy Tim Boland

4.1.10

Ask the Experts: Growing Healthy Trees

“Even trees do not die without a groan.” – Henry David Thoreau.

To stay healthy, trees require care. Think about it: Trees add beauty, increase property values, reduce cooling costs, provide food, replenish the environment with oxygen, block wind, create a habitat for wildlife, and filter pollution. That’s a pretty hefty job description.

We asked Tim Boland, executive director of Polly Hill Arboretum in West Tisbury, what Island homeowners need to know about keeping their trees healthy. Tim’s the consummate tree care answer man: He puts his graduate school training in horticulture and twenty-five years in the field to work every day on Polly Hill’s seventy acres of carefully tended public grounds. With more than eight hundred different trees to oversee, Tim’s a tough guy to stump.

Can’t trees just do their own thing?

Maybe, if their locations aren’t too close to any structure or part of the yard you use. But landscape trees, unlike forest trees, require a higher level of care to ensure their safety and aesthetics.

What kind of basic care do trees need?

Always remove the three Ds: dead, diseased, or dying limbs. Look for branches or leaves lacking vigor. Or deciduous trees (those that shed their leaves at the end of the growing season) with unusually early fall color. These are indications that a tree may not be healthy. You want to visually inspect your trees or hire a certified arborist, or tree expert, to do so.

Why prune trees?

Pruning is the number one topic visitors ask us about at Polly Hill. Keep in mind that pruning helps the plant – you have to be cruel to be kind. Trees, like people, decline over time. Pruning a tree from a young age establishes a framework of branches to keep it healthy and strong. We prune for a variety of reasons: to improve the tree’s structure; to minimize safety issues by removing limbs that interfere with wires, buildings, or high-traffic areas; to control size; to open vistas; to repair storm damage; to remove diseased, dying, or dead branches; to eliminate branches that cross or rub against one another; and to increase light penetration.

When should we prune?

In the dormant season. From about January 15 to May 1, you can see the entire structure of the tree without the leaves hampering your view. Bugs and pathogens are active in the summer, so you want to prune before they emerge. If your cuts are done right, they’ll seal over when the tree starts to grow again. Pruning at the wrong time can have disastrous results. Always consult a tree expert if you’re not sure when to prune.

What do we need to know about proper pruning technique?

Pruning is a combination of art and science. We teach classes in pruning at Polly Hill to dispel its mystery. Once you’ve determined which branches should be pruned, you want to use a three-cut method. All three cuts will be made vertically, not on an angle. First, cut no more than one-third through the branch, from the underside, at least three feet out from the main trunk. Make a second cut from the upper-side a short distance beyond the first. The limb should drop and break away cleanly, minimizing the possibility of tearing the bark all the way down the trunk. Now you have a three-foot stub that needs a crucial third and final cut closer to the trunk: Do not make a flush cut that would scar into the main trunk. Instead, cut just beyond what is called the branch collar, a distinctive area of rough ridges where the tree branch meets the main trunk. Specialized cells that live inside the branch collar will help heal and close the wound.

What are pruning no-no’s?

The inexperienced person will cut right into the live tree. But if you prune correctly – using the three-step method above – the tree will heal itself and grow back stronger. Problems also occur when people try to bend a tree to their vision or needs. You should never make indiscriminant cuts to lower or shape a tree. Never top a tree by drawing a line in the sky and hacking off large upright branches. Improper pruning can harm trees and lead to decay.

What role does mulching play in tree care?

Mulch locks in moisture, protects the root zone of the tree, and limits weeds. It also protects the tree’s bark from lawn mower damage. It’s very beneficial to young trees. Organic mulches add nutrients to the soil to help tree growth. If you use wood chips, make sure they are aged for at least three years. One of the best mulches is leaf mold, or aged leaves, generally a year old or more. Never mulch right up on the trunk. It will suffocate the bark, a living, breathing part of the tree. Spread mulch up to three inches in depth in a circular fashion, eighteen to thirty-six inches out from the trunk, depending on tree size, but never touching the trunk.

Is it important to fertilize a tree?

We’re making a concerted effort to reduce fertilizer use on the Island due to harmful run-off into our ponds. A tree will tell you when it needs fertilizer. Its leaves will appear stunted and dull green during the growing season, with limited shoot or stem growth. This indicates that the tree lacks nitrogen and should be fertilized. But never fertilize a newly transplanted tree. Wait until it is in its second or third year and monitor its growth. Apply only slow-release organic nitrogen, if needed. It’s less likely to run off into the Island’s aquifer and numerous ponds. Applying it each year is not beneficial.

Should we water trees?

Most of the soil on the Island is dry, gravelly sand. Gauge your trees’ water needs by the natural rainfall that occurs. Typically spring and fall have more rainfall and lower air temperatures, so less supplemental water is needed. The principal time to water is in the height of summer. When a tree needs water, the leaf stems will droop and cause the leaves to have a downward angle. Use drip systems or soaker hoses to water trees. Try and water deeply and less frequently rather than superficially and more often.

Certified arborists weigh in

While some homeowners are knowledgeable and handy enough to select the right trees and keep them thriving, both Tim Boland and Stephen Masterson of Polly Hill Arboretum agree that certified arborists are often your best call. So we asked two of them, Josh Scott, owner of Beetlebung Tree Care, and Mark DiBiase of Bartlett Tree Experts, a few key questions about what makes their jobs on the Island an ongoing challenge.

When does a homeowner need a certified arborist?

Josh: Even if you want to do the work yourself, it’s always a good idea to call in a certified arborist for a consultation. We’ll walk you through plant selection, placement, health care, and pruning. You’ll get good advice on which trees can do well in your specific location.

Mark: You should call in an arborist whenever you need tree work that’s over ten feet off the ground. We can also help with tree selection and planting – what will fit, where to put it, mature height and spread, and resistance to disease.

How should you choose a tree specialist?

Josh: Look for a certified arborist. Choose someone who specializes in what you need – some arborists work in dead or hazardous tree removal or in planting big trees. They have the expertise and equipment for niche projects.

Mark: Ask about certification. Verify their experience by checking references and be sure they have proper insurance.

What are the most common tree care problems you encounter?

Josh: Improper pruning, trees planted too close to houses or too low in the ground.

Mark: Improper pruning – too much taken out and incorrect cuts.

What tree care challenges are specific to the Vineyard?

Josh: Our coastal location makes trees susceptible to winterkill or salt spray, and our high winds and harsh winter scenarios cause Island trees to dwarf. The sandy soil leads to dry conditions. Deer pose a constant threat and we’ve just come out of a terrible cycle of caterpillar defoliation. With all that said, we still have a great number of healthy, magical trees on the Vineyard.

Mark: We have significant salt and wind exposure and numerous microclimates. We should use more hardy native plants as well as specimens that are deer resistant.

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