Tree rocking?

My sister called me and told me that her big oak tree rocks when strong winds blow. She says that the ground actually raises up around it. This area has had major hurricanes two years in a row and she wants to have the tree cut down. Its a beautiful old laurel oak. Could the root system be loosened so much that the tree rocks back and forth or is this probably in her imagination? The tree looks straight to me.

We've been through 3 hurricanes since building our house in 1985. The only trees that have ever become uprooted were oaks - really big oaks - oaks big enough to turn my car into scrap metal. I believe your sister.

Is the tree within reach of her house or anything else that could serve as a critical target? If so, or even if not, tell her to have an ISA-certified arborist inspect it immediately. If the tree really does rock at ground level, and it's not just her fertile imagination, she has a problem -- most likely Armillaria or some other root pathogen unless she has damaged the roots via construction activity.

Still, if it's a magnificent old specimen that otherwise appears healthy and it adds a lot to the appearance of her property, there are some anchoring techniques that might preserve it. There's no way to know that without a site visit.

Guy S.

The tree is about 20ft from her house. It does seem to be a shallow rooted tree. There are some of the roots that are growing on top of the ground. The only certified arborist around here is about 60 miles away. They would charge a fortune to come all this way, if they would come at all. It's a shame, we have several tree services in my town but none of them are certified arborist. Their idea of pruning a tree is to cut the top out of it. They have ruined several of mine.

If it rocks with the ground moving up and down, there are major roots broken underground and the tree is dangerous. I'd have it taken down if it is anywhere close to buildings.

Had a similar case over here a few years ago, a roadside elm started rocking in a storm, lifting the paving slabs 5cm or so with each gust. Phoned the city arbor squad, they said they'd send someone round to investigate (sounding like they didn't really believe what I was saying). As soon as they saw it, they took it down immediately (yes, while the gale was still blowing - they reckoned it was that dangerous).

I have a 85' Douglas Fir that makes me shake every storm. But the arborist says it's healthy and should stay there. Any way I would never cut it down, let it wreck the house. It shades me, gives me wonderful canopy to look up through, is gorgeous when covered with snow, the fragrance of the wind through it is perfect, and it survived the largest forest fire Montana has ever seen. In 1910 it probably was the only seed tree in the valley. Its children are now everywhere. How could I! I just move out of the sunroom when the wind blows.

Soferdig, you might want to have an anchor cable with shock absorption installed from about 2/3 of the way up the trunk down to a ground anchor 50-100 feet from the base of the tree, on the opposite side from the house. That way if it decides to fall, it will have to go in another direction. Connect it to a couple of CY of concrete poured in a hole in the ground, or to any other solid anchorage. Have it installed by a certified arborist -- or if there are none near you either, at least by someone whom you know is experienced and reliable (and insured). This has been done even at Monticello, the historic home of Jefferson.

Guy S.

Thank you Guy S. I have an arborist who is as emotionally involved with the tree as I am. Yes he is bonded. At this point its only rocking . We have done only light pruning to allow the force of the wind to pull the tree away from the house. Its anchor is still good. And our squalls come out of the Southwest pulling the tree away.

We have large, old black locust trees all around our house. During an unusually severe storm in January, many large limbs came down, as well as trees that were stressed or dead, but nothing over the house or other structures. In fact, a fair sized tree came down parallel and two feet behind our 40' wood/tool shed-nothing at all damaged! The locust trees closest to the house were limbed last summer. There is no heaving of the ground when these trees blow, but they are tall and sway a lot. Anyone with any experience with black locust trees? Except for the fact that they are tenacious once established, and every seed that falls becomes a seedling with thorns, I think they are magnificent trees with wonderful spring fragrance and "song" (because of the bees buzzing throughout the canopy), fabulous shade, interesting features, produce 100 year fence posts, and give long burning firewood. Thus, I want to protect those that are here, including the big ones near the house (opposing opinions in our household).

There is mixed opinion around here about the black locust being dangerous around houses because they have been known to just break. However, I think/guess it's because the trees were never pruned properly, so when the 90 degree branches get as big and heavy as trees themselves, they have to break or be supported. Comments?

This is my first post here. Interesting and informative website. I'm working on trees now, while brush can still be burned and dead limbs are easily visible.

Here is a photo off our deck of a locust limb that was cabled to another locust (on the left) to keep it from breaking. Perfect swing tree. It's definately living and always intiates comments from visitors.

Paws, a few things concern me here:

1. Black locust is subject to lucust borer damage in its native range, which weakens limbs and causes dieback. But you are well beyond the natural range of the locust, so I don't know if you have the borers out there. Ask yor extension entomologist.

2. You are concerned about 90-degree limbs, but those are the strongest. Be much more concerned about the narrow forks that frequently develop in locusts.

3. You say the trees near the house were "limbed" -- I'm afraid to ask what that means, but I hope it doesn't mean the trees were topped.

4. You don't mention what might have been done to the roots in the past decade or so. But most of those thorny seedlings you're finding probably are root sprouts, and they might (or might not) have been stimulated by root damage.

I think you should hire an ISA-certified arborist to inspect your trees, even if you insist upon doing the recommended follow-up work yourself. There is too much at stake here, and I'm not sure if you know enough about tree biology and pruning technique to go it alone.

Guy S.

Thanks Guy, you definately pegged my ignornance in this area. I especially am not a climber or a chain saw operator. I've had tree people out to inspect, and that is how certain trees were limbed. Nothing was topped. No one mentioned any borers. The two main people (professional arborists - certified?? - maybe) who looked at the trees last year, and one did some work on them, said the big ones looked healthy except for some dead/broken limbs and danger from those overhanging the house (mostly now gone). The photo is of the big trees closest to the house and except for one, which apparently needs some special equipment to deal with because of its position, none now lean toward the house, which is to the left and just outside the photo.

I tried to cut down and dig out some of the smaller trees (8" diameter max) in another area, which did cause the root damage you talk about. I did this after small, thorny trees were cut down and sprouted a dozen more as result. Around the big trees, there are no such thorny babies. Only where I tried to cut/dig them out are the thorny smaller ones.

I must have read wrong; what I learned about pruning was that the 45 degree angles were stronger than the 90 in general. Perhaps I got it backwards?

The basis of the 45-degree angle is that it's a recommended minimum. Wide angles discourage the trapping of bark between trunk and limb as each grows in diameter (called "included bark" in some books). Narrow angles (usually less than 45 degrees) often trap bark in this way, preventing the trunk wood and limb wood from maintaining a strong union. You can see this if you look at some limbs. If you see bark being pushed up out of the way (called a "branch bark ridge") it's OK, but if you see a seam between the branch and the trunk it means possible trouble down the road.

Guy S.

Thank you, Guy. Lots to learn and more to do and never enough $$ to work with! I very much appreciate your advice. I'll go out looking for branch bark limbs and seams. Laura