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Author Topic: Hemlock - All species bug/rot resistant?  (Read 458 times)

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Offline AnthonyW

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Hemlock - All species bug/rot resistant?
« on: September 11, 2017, 06:19:28 pm »
Subject says it all. Are all species of hemlock good for bug and rot resistance, or only a few species.

Primarily, the species in question would be on in New Hampshire, maybe Eastern Hemlock but I'm not sure, and its use as sides for a raised garden bed.
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Offline Bruno of NH

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Re: Hemlock - All species bug/rot resistant?
« Reply #1 on: September 11, 2017, 06:45:50 pm »
I have raised beds made of hemlock .
They been in for 6 years still holding up well
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Offline AnthonyW

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Re: Hemlock - All species bug/rot resistant?
« Reply #2 on: September 11, 2017, 06:51:57 pm »
Hopefully they are both the same species.

My neighbor is looking to take down a few tress in order to setup a bunch of raised beds when it occurred to me one of the trees is hemlock.
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Offline Bruno of NH

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Re: Hemlock - All species bug/rot resistant?
« Reply #3 on: September 11, 2017, 06:54:48 pm »
I'm in NH
We only have one hemlock I know of.
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Offline plantman

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Re: Hemlock - All species bug/rot resistant?
« Reply #4 on: September 11, 2017, 08:13:32 pm »
Here is a link to a good research article someone shared with me. It might help you.
https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_02.pdf
I believe that while hemlock does possess some natural insect fighting properties it might not be rot resistant when used outdoors because water can penetrate it. I've often seen hemlock used for sheds and gazebos but those are structures with foundations. If you're looking for rot resistance locust and white oak are excellent.

Offline Don P

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Re: Hemlock - All species bug/rot resistant?
« Reply #5 on: September 11, 2017, 09:22:55 pm »
I wouldn't call it particularly resistant in either category, better than pine but that's about it.
Yours would be eastern, we have eastern and a few Carolina hemlocks in the mountains of VA. The Carolina has wide open almost splayed back petals on the cone where the eastern just opens enough to drop the seeds.

Offline plantman

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Re: Hemlock - All species bug/rot resistant?
« Reply #6 on: September 11, 2017, 10:02:41 pm »
I wouldn't call it particularly resistant in either category, better than pine but that's about it.
Yours would be eastern, we have eastern and a few Carolina hemlocks in the mountains of VA. The Carolina has wide open almost splayed back petals on the cone where the eastern just opens enough to drop the seeds.
Interesting, it's been a long time since I took plant identification classes so I have to keep pushing myself to learn and wood working in one way.
Whenever I cut eastern hemlock down I find it's a heavy dense wood that feels like it would be quite strong , at least as far as soft woods go. And I notice that it is hard to split. The grain seems to have a twist to it.

Offline Don P

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Re: Hemlock - All species bug/rot resistant?
« Reply #7 on: September 11, 2017, 10:30:38 pm »
If you know nothing else about a piece of wood density is a pretty good indicator of strength and the mechanical properties most of the time but doesn't equate to durability or insect resistance though. That usually has more to do with the extractives in the wood. The extractives are deposited in the heartwood. I don't know of any sapwood that is decay resistant but a number of species heartwood is durable.

That doesn't mean hemlock wouldn't make a fine raised bed, but there are probably other woods that would last longer. My wife just snagged a bunch of red oak slabs for garden edging, it will last until it fertilizes the soil and she'll grab something else.

Offline plantman

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Re: Hemlock - All species bug/rot resistant?
« Reply #8 on: September 13, 2017, 05:11:50 pm »
As I understand it, red oak is porous and will rot quickly. White oak will hold up much better because it is not porous. Hence the reason they use it for ship building.

Offline Don P

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Re: Hemlock - All species bug/rot resistant?
« Reply #9 on: September 14, 2017, 05:49:58 am »
I imagine the tyloses do help with decay resistance but are not the primary reason. The extractives content of white oak is about half again higher than in red and of different types. White oak has a lot of tannins. Chestnut oak doesn't have a lot of tyloses, it is porous which is why it is rejected by barrel makers but it was a major source of tanbark . It is also known as "sill oak" somewhere you want a durable wood. This was from a quick google

Quote
WOOD DURABILITY AND ITS CHEMICAL BASIS
Concentrations of extractives in some important commercial timbers are shown
in table 1. These values should be taken as indicative as they may be subject
to large variations due to the presence or absence of sapwood in the samples and
the heterogeneous nature of heartwood. Nevertheless, it is observed that durable
woods usually contain more than 10 percent extractives, whereas, perishable woods
contain less than 8 percent extractives.
...
Many fungitoxic extractives identified in extracts of various durable woods
are phenolic compounds. The toxicity of stilbenes identified in Pinus Spp.,29,30
Eucalyptus spp.,14,31 and osage orange (Maclura pomiJera)32 is particularly well
documented.33 Cryptophenols (derived from terpenoid metabolism) were shown to
contribute to the durability of incense cedar (Libocedrus decurrens).6 Similar cryptophenols
in the quinonic form were also found in heartwoods of Dalbergia spp.34
Naphthoquinones and anthraquinones were identified in Tectona grandis and may
contribute to the protection of its wood.35,36 Lignans like plicatic acid are involved
in the decay resistance of western red cedar (Thuja plicata)37,38 and flavonoids in the
resistance of Salix caprea.39 Polymerized lignans in redwood (Sequoia sempervirens,
Hergert, this volume) previously confused with proanthocyanidins7 and ellagitannins
in Eucalyptus spp.40 or white oak (Quercus alba)41 are probably responsible
for the durability of these woods.