When are my trees too tall, and what can I do about it?

We have six very large and apparently healthy poplars that are like 100 feet or so tall. Every time the wind blows, I wonder if they are coming down. I really would like to trim and cut them back. What do you think?

— Jan

Tall, mature, healthy trees are usually not too big of a worry unless there are some existing structural conditions in the tree that would cause concern.

The best way to determine this is to bring in a certified consulting arborist to look at the trees to see if there are problems and what could be done about it. Someone like this usually doesn’t do any tree pruning, they just evaluate the tree and advise you on what to do. You’ll have to pay for this service, but it’s the best way to really know if you have a ticking time bomb in that tree.

A second option would be to call a quality tree trimmer who can come out to advise you on what to do. The advantage is that they usually won’t charge you for the consultation if they do the tree trimming work. The disadvantage is that you really need someone trustworthy so that you’re sure they’re not just suggesting things to do to the tree just to get more work (and more money) from you.

I only would have a tree trimmer licensed by the city of Grand Junction do the work for you, even if you live outside the city limits. People licensed by the city have to show proof of insurance and demonstrate they are competent tree trimmers to the city forester. Also, going through the licensing process tends to weed out the “fly-by-night” operators that usually end up doing a poor job.

You can pick up a current list of people with a class “A” forestry license at the city parks office at Lincoln Park. Call 254-3866 or go to the Grand Junction Forestry website at gjcity.org/Forestry.aspx and click on the “Licensed Tree Care Providers” button.

One thing I want to warn you away from is a practice called “topping” your trees. This is where the main vertical stem and upper primary limbs on mature trees are cut to stubs at a uniform height. People often do this to large trees because they fear that the tree is getting so big that it might break and fall.

If you have your tree properly evaluated as I’ve outlined above, that shouldn’t be a worry.

However, there are several very good reasons why trees should never be topped. First, it reduces the tree’s food-making capacity. Trees require a large leaf surface area to provide food for maintenance and growth. Topping cuts off a major portion of the tree’s food-making potential and depletes the tree’s stored reserves from the branches that were cut off.

Second, topping stimulates undesirable “water sprout” growth. Topping a tree stimulates the re-growth of a dense brushy mass of unattractive, upright branches (water sprouts) just below the pruning cut. Water sprout regrowth is extremely vigorous. A topped tree will rapidly return to its original height, but will lack its original form.

In time, topping actually will create a more hazardous tree. This water sprout growth is weakly attached to the main branch and is much more prone to wind or storm breakage. In addition, the large branch wounds left from topping are slow to close and therefore more vulnerable to insect attacks and fungal decay. An invasion by either pest can spread into the trunk, killing or weakening the tree.

The last reason not to top a tree is that it disfigures the tree. Ugly branch stubs, conspicuous pruning cuts, and a broom-like branch growth replace natural beauty and form. It turns the tree into a freakish shadow of its former self. Topping can reduce the real estate value of your trees by 20–100 percent.

A correctly trimmed tree increases in value at each pruning. So if you’re considering topping, please, please, please reconsider.

To be honest, pruning very large trees such as yours is pretty tough for the average homeowner. You need to get up high into the tree using chain saws. It’s delicate and dangerous work. It’s almost always better to hire a tree service to do the pruning for you. They have the equipment and experience to do the job properly and safely.

Dennis Hill is the nursery manager at Bookcliff Gardens, bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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