Wind resistance and Conifers.

[UnityArborist]

I was wondering what the general consensuses on how effective thinning is for reducing wind resistance in conifers? I had a big wind storm come through and knock down a bunch of big trees. I have clients asking me now what can we do to prevent this. I would like to be able to tell them with some certenty what would help.

Also I went out on a bid that had 22 incense cedars in a row. Some of the trees have grown large and others are more spindly and distorted. My question is will removing the smaller trees and opening some space between the larger trees beneficial to the remaining trees?

My thinking is that wind will be able to more around and through the trees, and not just batter into them. Is this thinking flawed, or am I just over thinking this job.

 

[clearance]

Check out windfirming. It works.

 

[John Paul Sanborn]

The first hing you need to do is assess the root-plate's integrity and proportion. If you have a conifer too close to a structure, or burried utilites, there is a good chance that the trees stability is compromised.

I've been sold on windfirming in riparian boundaries, but topping a landscape tree is still too hard to swallow. Even though this really just follows the natural process. We look at old trees in the wild and talk about how the top was blown out years ago...

I still have to go with spiral pruning an tip reduction, for aestetic reasons.

 

[clearance]

You don't have to top them, you could reach up with a pruner or saw head on a stick and windfirm the top.

 

[bendtrees]

Interesting thread Unity.
I think you will find more info in here and Buzz if you search for it. I often wonder on a basic level how effective we can be at this.

I figure the physics of trees and wind interacting are somewhat complicated when you figure in how trees oscillate and use what I would call ballast. I don't know much about "windfirming" but it seems like it is a proven method for non-urban areas. Its pretty easy to just look at leverage and the "wind sail" of the upper canopy and figure that risk of failure can be reduced by X. I suppose my life experiences lead me to think that it is really hard to improve upon nature, hence I'm fear messing it up.

Perhaps planting guides for windbreaks in the plains areas would be of help? You know how every wheat farm in the country has rows of different height trees out there? If you can adapt those models into your situation,???

Anyway, that's my two cents. Would love to see more science on this. I remember an Aussie study on wind and big trees, but I believe it was somewhat inconclusive about the results of thinning. I could be wrong, but I also remember not having that much confidence in the study???

Give me a shout if you need help over the hill. Its a bit quiet over here!

 

[bendtrees]

Better idea, if you have time on your hands...

six pack of beer
Minature trees from hobby store, or branch cuttings.
re-create landscape
fire up blower/fan/shopvac....
have fun

 

[sgreanbeans]

Yes more science would be cool.
I am from IOWA! Lots of farms with wind/snow breaks. We do a lot of removal on these as they often become ineffective when they mature. They plant them way too close, then 30 years later, they don't understand why half of them are just sticks in the wind or all the tops have been removed via Super Cell!
I try and tell them that they need to care for their trees as they grow, too keep the integrity of the line. They just think I'm trying to spend their money!

 

[sgreanbeans]

Typical wind/snow break, West side of homestead
line 1 farthest away, Norway Spruce
line 2 middle, Colorado Blue Spruce
line 3 closest to house,Techny/Emerald Arborvitae

Not sure why they put the Arbs there, many times they grow faster than the Blues, I would put them in the middle to fill in the gaps at the bottom of the Norways, but Im not a farmer

line 4 cows

 

[John Paul Sanborn]

USFS/USDA has a better IMG file, but this one comes from http://www.fao.org/docrep/t0122e/t0122e0a.htm

for a truely effective windbreak you need 2-3 levels of tree/shrub rows to ramp the flow up over the tops. otherwise you have a dam on the windward-side and lots of turbulence.

So say you are using arbs, you may want globes followed by a short columnar followed by a tall pyramidal.

 

[sgreanbeans]

I see, there are a lot of globes or other small evergreens and shrubs around these lines, I have always associated them with landscape than actual purpose, now I know, once again JPS, you have taught me something new!
Thanks

 

[John Paul Sanborn]

I see, there are a lot of globes or other small evergreens and shrubs around these lines, I have always associated them with landscape than actual purpose, now I know, once again JPS, you have taught me something new!
Thanks

Thanks! Now I'm not saying that that is what they planted them for. If they are on the leeward side of the windbreak, I think you can count that out

BTW Hawthorn's with too, anything low with a tight canopy that will ramp the wind up over the last row will work. Also, i agree with you that they are not managed and can be planted too close.

A tall spruce that is too close to the house has a good chance of going over in a vagrant wind. I've seen vortexes created between tree-lines and abodes that have caused damage that you can diagnose.

 

[clearance]

The picture shown is not of windfirmed trees. Windfirmed trees let the wind go through them. Imagine carrying a sheet of plywood in the wind, then the same piece with big holes in it. That is windfirming. I have seen windfirmed trees standing after violent and sustained winds have blown down similar trees that were left alone.

 

[Bermie]

Something to think about if you want to remove the spindly ones...by opening a gap, will the remaining ones be able to withstand the increase in exposure to the wind? If they have grown up in association with the small ones they could, I only say could, be weaker on that side and become more vulnerable to going over...

Add that to your deliberations...only you have eyes on the job!

 

[John Paul Sanborn]

That is windfirming.

Post a description of the process, I've been reading it as "spike up and blow out the top" for the past few years. Sounds more like a spiral prune.

The diagram I posted is a planned wind break, you do not want the wind to go through them, but up and over. As i said, if you do not have a succession of heights then you have the plywood effect you describe, along with the resulting turbulence. It is that turbulence that causes a lot of the storm failures we work with.

you plant the windbreak so that it is near the edge of the protected zone to allow a good root plate to form on the trees. The same principle as with snow and sand fencing, except that with the fences, the windward turbulence is the ramp that carries the matter over the protected zone.

 

[clearance]

JPS, yes, it is like spiral pruning. In the bush we topped them, but I don't think you have to, it would just take longer not to. But that would be justified in a residential setting. You are on the right track, having the wind come in and roll over. I guess you would have smaller, bushy trees in front. Then taller ones behind where the wind is coming from.
Sometimes winds come from directions they never do, these freak winds do a lot of damage as well. I would make sure the site can drain excess water as well.

 

[John Paul Sanborn]

I would make sure the site can drain excess water as well.

So true, we all have been to sires where Colorado spruce are struggling with wet feet. Put a little leverage on the top and you have a recipe for uprooting.

Winds do vary but when you get out on the plains the prevailing winds in the winter are rather consistent. The planting of windbreaks is as old as people building house in the wind. With new highly efficient construction they are becoming counter productive, especially if they are trying to put some sort of solar collection on the house.

I saw one that was so old that the neighbor had problems with the sparks form his chimney blowing into it, some huge Norway spruce.

 

[derwoodii]

Here's a bit of science on the topic.
http://www.amjbot.org/cgi/content/abstract/93/10/1522

and interesting story to tell with this paper, the fallen gum was one I climbed trimmed and cared for whilst working at the campus grounds for some years. Got my throw bag hooked up on the 3 third floor window sill.

http://isaitalia.org/index.php/Download-document/52-James-K.html

 

[sgreanbeans]

very cool stuff on the links, thanks