I am resigned to the expense of that, then. I hoped to use several inches of something less expensive - say, gravel or peanuts. Or a false bottom, or something. :-)

For most plants you need at lest 12" of good fill. Some will do ok in less but going for the full 12" depth will be worth it in the long run. And fill it right to the top.

Dave

digdirt, I take your point and will fill the planter to the top. But my question is, if the raised bed is 18" deep, for example, can the bottom 6" be some material other than soil?

I didn't realize the bed was 18" deep since you didn't mention that. But the answer is still no. Layering different types of soil creates drainage problems, water ponding, and rooting issues. And 18" deep is even better than 12".

So then the question becomes what to use to fill it with (lots of discussions here about that question) to a depth of 18" that can all be mixed well together first, not layered. There are many ingredients, all with different price ranges - some free, some cheap, and some much more expensive - that can be mixed well first and then the bed filled.

So what do you plan to use for fill?

Dave

Okay, that's clear. I suppose a soil/compost mix. I'll look some up here. May I ask also: would you put something under the whole thing, like weed cloth or plastic sheeting, or would it sit right on the bare ground?

Something under - some sort of bottom - is not recommended for the same reasons - interferes with drainage, causes water ponding, and root issues. With the exception of if you have gophers some will use metal hardware cloth on the bottom to keep them out. But never plastic or landscape fabric.

Others may set the beds on top of a couple of layers of cardboard to kill bermuda and other invasive grass/weeds from moving up into the bed. The cardboard decomposes within a year usually.

But most just set it right on the bare ground and if possible even fork up or till several inches of the base ground to improve the drainage.

Dave

Many thanks!

I do a lasagna style raised bed without sides so I like Dave's suggestion of using cardboard. I use a layer of wet newspapers to kill grass, maybe about 6 sheets thick.

digdirt2: Why one should never put landscape fabric? Funny enough that's exactly what was recommended to me in another forum. I also have 1/4 chicken wire to avoid rodents. I am glad about chicken wire as I found few attempts to dig under beds.

WHat one would do if fabric is already there? I am not sure I would mount/dismount beds in the middle of the season though:)

thanks