The sidewalks of my neighborhood are filled with stacks of cedar planking from fences blown over in hurricane Ike. Being a cheap fellow, I hauled a bunch of them home to make some more raised bed/square foot gardening boxes. I made the assumption that cedar wood fencing ISN'T treated with anti-rotting agents but now I'm second guessing myself. Are cedar fence planks chemically treated or are they safe to make gardens?

How about the 2x4's? I assumed they ARE treated pine and I shouldn't use them on the inside of raise beds.

Thanks,
-Blast

I don't know for sure, but I doubt it. Most treated lumber is pretty obvious and most cedar is intended for cosmetic uses and also is considered intrinsically weather resistant.

OTOH, I suspect you'll have a fairly limited lifespan in direct contact to moist earth, esp. with 3/4" thicknesses.

But if it's free, what the hay.

Dunno about the 2x4s. Most fencing around here uses cedar 2x4s, but your situation might be different.

As a counter point, if this is re-cycled, some of it may be treated by the home owner (deck sealer or similar), although chances are pretty slight.

-john

I've got quite a bit of cedar fencing around my house, none of it came treated. Given it's natural resistance to rot, etc. I can't imagine that the stuff you've found would be. If it's been painted or stained, all bets are off.

Same with cedar tubafors...redwood ones too for that matter...

John E

You never want to put Thompsons on any wood that will be used in a garden as the chemical (like most) will leach into the soil.....then into the food.

To answer the OP's question, I have never seen or heard of cedar fence planking treated with any chemicals or pressure treated so I called my friend who is the manager of a 3rd generation family owned lumber yard, he says it has never seen it come through their yard. Given the natural resistance of cedar from rotting does not make it cost effective to treat.

In my own garden, we have cedar lined beds that are now 6-7 years old and have no signs of rot and we are in the rain prone PNW area....

Why not line the inside of your planters with heavy plastic sheeting used for making ponds? Just regular 4 or 8 mill sheeting might last long enough to get you through a planting or two. That way if the wood is treated it will not be in direct contact with the soil.

From what I understand Blast cedar isn't treated because of it's natural resistance to rot.

In fact, I pulled up my old beds (treated pine fence boards - trying to do it on the cheap) when I realized the leaching problem, and am planning to rebuild them with cedar boards.

I built mine 3'x 6' by just driving stakes at the corners and securing the boards to the stakes. The 3' width was manageable (I could reach in from either side easily to weed / harvest my goodies).

Blast: I would use the cedar in flower beds. As others said, I've read it's naturally resistant to insect infestation and certain molds and, while it will rot, it's more resistant (like redwood) to rot than most other woods.

+1 Ray's idea to line the beds with plastic. You may want drain holes on the bottom, depending on rainfall.

FYI - Made raised beds out of plain old untreated pine, no sort of waterproofing used at all. 5 years and still going (though showing fair amount of rot).

Made a compost bin out of cedar leftovers (for the frame), 8 years and no sign of rot at all - even on the bottom.

This is in St. Paul, MN - winter climate.