Pressure-treated wood for grow boxes?

[AcerAddict]

Is pressure-treated wood (yellow pine, in my case) safe to use for grow boxes? I'd let the wood dry thoroughly first, but I was just curious if the chemical used in pressure-treating wood is harmful to trees at all.

Currently, it seems that ACQ (alkaline copper quaternary) is the main chemical used in treating wood in the United States. According to the EPA...

ACQ (alkaline copper quaternary) is a water-based wood preservative that prevents decay from fungi and insects (i.e., it is a fungicide and insecticide). It also has relatively low risks, based on its components of copper oxide and quaternary ammonium compounds.

Water-based preservatives like ACQ leave a dry, paintable surface. ACQ is registered for use on: lumber, timbers, landscape ties, fence posts, building and utility poles, land, freshwater and marine pilings, sea walls, decking, wood shingles, and other wood structures.

I would think these chemicals wouldn't be harmful to trees since pressure-treated wood is used as landscape borders all the time. I'm fine with using standard pine instead if I have to though. I could also try to get my hands on some cedar boards as well and make boxes from those. Just trying to think of something that will last a few years sitting outside getting rained on all the time or baked in the sun without getting moldy or attacked by insects.

 

[Colorado]

I have used both pressure treated and raw lumber for grow boxes. So far, I have not observed any noticeable difference in the health of the trees or any adverse effect from the pressure treatment. The sample size is only about 3 years, though.

Still, I no longer use the pressure treated wood. I just use raw pine or fir or cedar now. It does warp a little more than the treated wood, but I have to think that in the long run the chemicals in the treated lumber probably are not helpful to the tree or the microbial system in the container.

I would recommend the raw cedar.

 

[Tieball]

I’ve used pressure treated wood for growing box sides and bottoms for more than 15 years. I have never experienced any problems. And, the boxes last a long time. My boxes are outdoors in all seasons with direct exposure to all of my climate has to offer. The boxes also sit on the ground all winter buried in snow and ice.

The experience opinion I have is from actual constant use for years.

The trees I have in boxes are all healthy.

 

[Cajunrider]

Unless you plan to consume your trees, I would not be concerned at all about using pressure treated lumber for grow boxes. I've done that for years.

 

[AcerAddict]

Thanks for the feedback. A good portion of my plants are small enough that they'll fit into terracotta bulb pots in the spring, but I have several that are big enough to each require a grow box.

 

[penumbra]

I have been using pt wood for planters and raised beds for about 40 years. It used to be made with some sort of arsenic compound which is really bad to burn.
One of my large grow boxes has had a Japanese 5 needle pine in it for 33 years.
Look in the archives. This has been talked about quite a bit here.

 

[Brian Van Fleet]

Yep, good to use.

 

[Katie0317]

When I see pics of wood boxes on BN, I wondered if there was a basic formula in terms of size and design? I remember seeing ones that I think were built by @Pitoon (I may be mistaken) and they were beautiful.

I wondered what size you usually build them and anything you've learned along the way that you can pass on. My husband would be happy to build them but I'd like to be able to give him some direction as to what's worked best for others.

@AcerAddict This article may be of interest to you...It's about wooden grow boxes.

Wooden growbox for bonsai, why?

Yesterday I built a few wooden growboxes to repot my future bonsai trees in next year. I put a picture of them up on facebook in a bonsai beginners group and immediately got a few questions from pe…

shumibonsai.wordpress.com

 

[Pitoon]

When I see pics of wood boxes on BN, I wondered if there was a basic formula in terms of size and design? I remember seeing ones that I think were built by @Pitoon (I may be mistaken) and they were beautiful.

I wondered what size you usually build them and anything you've learned along the way that you can pass on. My husband would be happy to build them but I'd like to be able to give him some direction as to what's worked best for others.

@AcerAddict This article may be of interest to you...It's about wooden grow boxes.

Wooden growbox for bonsai, why?

Yesterday I built a few wooden growboxes to repot my future bonsai trees in next year. I put a picture of them up on facebook in a bonsai beginners group and immediately got a few questions from pe…

shumibonsai.wordpress.com

If your hubby makes them you want low and wide, similar to an Anderson flat.

I made these for some JMs. Growing these JM for mame and shohin.

 

[Katie0317]

It was you. Those are beautiful!

Why should they be low? I think I understand wide (for the roots?) but I'm not clear as to why they should be low. Are those about 12x12? I can't tell by looking so am guessing. Really nice.

I always say, "The way you do anything is the way you do everything." I believe that's true. Your pots, tool rolls and the boxes. Well designed and beautifully executed.

 

[Pitoon]

It was you. Those are beautiful!

Why should they be low? I think I understand wide (for the roots?) but I'm not clear as to why they should be low. Are those about 12x12? I can't tell by looking so am guessing. Really nice.

I always say, "The way you do anything is the way you do everything." I believe that's true. Your pots, tool rolls and the boxes. Well designed and beautifully executed.

Thanks for the kind words.

Yes, they are 12" x 12" x 3.5".

You want the boxes/pots low so the roots grow out radially and not downwards. Unless, your are trying to grow out for neagari bonsai which then you would use an extra tall and narrow pot or tube of some sort secured onto a pot.

 

[Katie0317]

Thank you. I think that sums it up. You've helped me and I hope lots of others will benefit too.

 

[Tieball]

I only use the pressure treated lumber 1x4 or the 1x6. I would all that I never fill the boxes entirely with substrate or soil. I place about a 1” layer on the bottom, place the tree, and then only fill to a point usually about 1” above the root line. The height of the mix varies because of root needs. I’d say on average I only fill about 3/4 of a box.

After substrate I add a mesh screen with a hole for the tree cut out in the middle. I cut a line from a side and then cut a hole resembling the trunk diameter at the substrate level. The screen mesh is a standard pet-proof screen available at Home Depot type stores. It serves several purposes for me: it shades the substrate keeping it cool on hot days; it keeps a more constant temperature below the screen; it stops erosion of the substrate that can happen when watering so roots remain covered; and, it stops bird and rodents from pecking at the substrate.