Help me build a raised herb garden bed

March 13, 2008 4:57 PM

Help me construct a 3' tall raised herb garden in my backyard. Materials? Subtrate Levels?

We have a boxer puppy that loves chewing on plants and sticks. We want to build an herb garden with basil, oregano, chives, and maybe one or two more.

I'd like to build a raised garden bed about 3' high and maybe 5' wide x 3' deep, against the back cinder block wall with Castlewall brick. Do I need to use rebar to stabilize the brick wall so it doesn't expand? Do I therefore need to find bricks with holes in the middle or is there another strategy? Should I be using a cedar wall construction instead as seen here? What sort of substrate levels should I use so the soil can drain properly and not rot? Do I need to put something like river rock as the bottom layer? I'm also thinking of a cosmetic touch: lining the side walls with a reed fence.

Are there any other potential issues I'm overlooking? I have minimal construction/gardnening skills (first spring in my first house!), so be layman, please.

posted by blastrid to home & garden (8 comments total)

I can't answer any questions about brick. I put some raised beds in my yard using redwood 1x12s, attached to 4x4s (which I'd recommend over brick, but mostly for aesthetic reasons). They've held up for 4 years, and I can see them going 4 more.

You might need a substrate for the brick, so that it doesn't settle (again, can't answer that), but you won't need one for the soil. Three feet is waaaaaay deeper than herb roots will go. For herbs, you could get away with 12-18 inches and be just fine. Three feet of nice, loose soil will provide plenty of drainage, regardless of what's underneath it. (Unless it's concrete or something.)

When you bring in soil, make sure you get equal parts topsoil and compost, then mix them. Any topsoil you buy is going to be nutritionally insipid. The compost will help the plants thrive.
posted by mudpuppie at 5:16 PM on March 13

There are a bunch of web sites with plans and diagrams for building accessable raised platform garden beds that are specifically for disabled gardeners. The growing area is essentially a container bed raised up on some sort of supporting structure similar to a work bench. You could possibly get a cheap table at a thrift shop, paint and decorate it and just grow your herbs in a variety of flower pots on the table. If your puppy would chew wooden table legs a metal work bench might be better. The area under the table could be used for any number of things.
posted by X4ster at 6:25 PM on March 13

If you're laying bricks with mortar, you shouldn't have any problems, but if you're stacking them dry it's less certain. This Oldcastle brochure seems to think you'll be ok with a layer of sand behind the brick, I imagine as a drainage layer. If the soil behind the wall isn't too heavy you should be fine.
posted by electroboy at 8:37 PM on March 13

1x12s, attached to 4x4s [...] They've held up for 4 years, and I can see them going 4 more.

I've got the same, but I'd go with 2x12s next time. It's been more than 4 years (though less than 8. Honestly, I forget) and they're showing their age. Bulging and bowing. Err on the side of caution if you decide to build with wood and can afford it.

Are there any other potential issues I'm overlooking? I have minimal construction/gardening skills

You could get complicated with it and bury PVC to feed a drip irrigation system, but honestly, don't overthink things at this stage. If it's your first real garden, better to start simple and low tech.
posted by mumkin at 1:01 AM on March 14

I have redwood 2 x 12s and 4x4 posts. 24" high. Some beds are 4' x 4', others are 4' x 12', posted every 4'.
Your 36"h should keep the pup out, but ofcourse you'll need to fill with that much more soil.
Start with a layer of sand at the bottom.
I think you may have some trouble stabilizing the brick, unless you use mortar (can mortar be used with Castlewall?). Rebarring all that brick will be a huge pita.
Reed fence: not sure if you mean to put them inside the beds, but they will rot quickly if you do. Around some beds I use a little 18"h wire edging folding fence to keep my Golden out of the tomatoes, peppers and beans.

If you decide to ditch the bricks:
Having had these raised beds for 8 years, I found that the 4x4 posts will start to rot first. I'm looking forward (rolling eyes) to rebuilding some within the next couple weekends. Do try to fasten them correctly, I suggest using galvanized screws w/big flat washers. Galvanized angle brackets on the interior side. Stay away from treated lumber which may leach into your good soil. Use redwood or cedar. Good luck!
posted by artdrectr at 1:56 AM on March 14

Assuming you are using these materials because appearance is important, rather than cheaper solutions like a table with pots. I expect you will be fine with no mortar and no reinforcement. I have had loose cinder blocks to a depth of two feet,and they are pretty stable. You might need to dig a bit out after a few years and straighten them up again if they become dislodged over time, but I would take that, with the accompanying healthful decompacting of the soil rather than over-engineering a solution that will last for decades. Certainly the plants are very forgiving and they won't care. Similarly, you won't have any drainage issues. Just get out there and do it! The worst that can happen is you need to reassess in a few years, which you might anyway, if your dog grows.
posted by bystander at 3:30 AM on March 14

Some great ideas here, thanks everyone.

An even lower-tech route, as mentioned above, could be a short wide table, and I could cover the space underneath with the reed fence. So from the outside it'd appear as a fully constructed rasied bed, without all that extra depth of substrate, but I think I'd build up a cedar wall on top instead of seperate pots. Underneath could be drainage holes, or storage for gardening tools, supplies, and soil.

I think the brick job would be too big. Low-tech with a hi-tech appearance is more suitable for my skills and my budget.

MUCH APPRECIATED! Gonna get to work on this over the weekend, enjoying the lovely 75º weather.
posted by blastrid at 2:37 PM on March 14

Garden beds more than four feet wide are difficult to reach into to work. I like wooden raised beds bolted together so they can be taken apart more easily. I see where you're going with the table thing, but I think a raised be is better for your plants, soil, &c. The table thing will require more water then a bed that has contact with the underlying soil. It will also experience more temperature extremes.
posted by oneirodynia at 3:23 PM on March 14