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Make Your Fence Posts Last

By
Real Estate Agent with Maximum One Realty Greater Atlanta

There comes a time when every gardener needs to set wood in or on the ground.   A weekend garden expansion project at my own home has us doing exactly that.

Perhaps it's a solitary post stapled loosely with chicken wire to which a clematis or trumpet honeysuckle vine can cling. Perhaps it's one of many posts joined by high fencing to persuade deer that they can more conveniently eat from neighbors' gardens. Perhaps it's the wooden sides of your compost bin.   When undertaking a garden project it's important to keep a few things in mind when selecting and installing wood posts.

Wherever wood is exposed to moisture, it rots. Those same bacteria and fungi that keep our planet from being overrun with an accumulation of dead branches and tree trunks are not so welcome at our fence posts and trellises.

Fortunately, many ways exist to slow wood rot in the garden.

For finished lumber, most people these days opt for pressure-treated, or PT, wood. True, PT lumber should not rot for decades, but there are hazards associated with its use. Take care not to breathe any sawdust generated when working with this lumber, and dispose of it in the trash, not the soil.

Wood preservatives are generally toxic to more creatures than just wood-rotting bacteria and fungi, in varying degrees. Think twice before applying a preservative to wood, or using a wood treated with preservative near a vegetable garden or children's playground.

Long before chemical preservatives or PT lumber were available, farmers had other ways of preserving fence posts. One traditional method was to char any parts of a post that would be in or near the ground. Bacteria and fungi have a hard time digesting charcoal, so decay was put off as long as the charred coating remained intact.

Another method was to stick the post-to-be in the ground upside down, on the theory that a piece of dead wood would suck in water in the same direction as it did when it was a part of a living tree. This is far from proven, though.

Then there are woods that are naturally rot-resistant.

If you are using finished lumber, you may be restricted to choosing from among red cedar, redwood, white oak, perhaps cypress. If you can use unfinished wood - posts for a rustic pergola, for example - you can expand your palette to include such woods as black locust, osage orange, white cedar, chestnut and walnut. Black locust, osage orange, red mulberry and Pacific yew might be expected to last in or on the ground as long as PT lumber!

Note that it is the heartwood - the old, interior portion - of any tree that resists decay. So even though western larch and douglas fir are only moderately rot-resistant, the large proportion of heartwood in every log makes these woods suitable for many outdoor uses.

In contrast, Eastern red cedar is very rot-resistant, but - especially when young - has very little heartwood. Dig up an old cedar post and you will find the sapwood eaten away to a heartwood skeleton of the trunk and remnants of old side branches.

As long as the soil is not frozen, it's fine to dig holes for garden structures and ornaments. Choose your wood carefully. And consider sticking any posts in the ground butt end up and charred!

 

Comments (1)

Steve and Jan Bachman
RE/MAX Gateway, Reston, Herndon, Ashburn, Sterling, Fairfax - Herndon, VA
Realtors - Northern Virginia

Good charred post. Anne. I set a fair # of fence posts as a kid. My parents were avid gardeners.

You have given me the idea of doing some blog posts on gardening topics. Much of the knowledge I take for granted because of my country background, is totally new to our clients (and my children sad to say)

Mar 14, 2011 04:44 AM