If these planters are sitting flat on the ground why put a bottom in them at all. If you are building a planter box that is up off the ground and plan to put perennials in it you'd better not live where it freezes or you'll have to insulate the boxes with solid foam insulation. Planters off the ground where it freezes get the cold from the bottom as well as the sides and there is nothing to protect the plants roots. In the ground they are protected from freezing so hard by the soil all around them.

1 foot wide is not very wide to put perennials in. You have to take into consideration what goes on under the ground as well as on top. If the roots can't spread out the top growth won't be lush because the roots will be constricted. I suggest you revise your plans into 1 bed and plant taller plants at the back and shorter ones in front.

hm...shoot. Obviously I'm not good at this. It freezes here for sure.

Regarding why there is a bottom on them, I want a bottom in it so I wouldnt have to have planters that are 3 feet tall full with dirt. The "bottom" would actually be a couple feet upThat's expensive and I would have to ad extra reinforcement so the wood wouldnt bow out. I just want it to "look" like they are 3 feet. Clear as mud? would 3 feet wide work?

assuming I make them wider, and insulate, how deep does my soil need to be, knowing the bottom will be wood. And what are your thoughts on the drainage situation?
Thanks

We just remodeled our house and it is now nice and contemporary. I am staring at the post-construction dirt and wondering how to create a garden to go with a more modern house. So I understand where you are coming from.

Three feet wide would definitely work. I would skip the false bottom idea though, it sounds like it would be inviting trouble. Over time, the bottom is sure to rot, as it will be wet all the time. I suppose you could use pressure treated wood, but yuck, why go the chemical-laden route.

If it were my house I would fill the planters with soil their full depth. If money is an issue you could get cheap soil to fill the bottom 2" and then nice soil for the top foot. You could also compromise and make the containers smaller.

Another idea: you could take up some volume at the bottom of the containers by putting rocks or old concrete in there.

Yes, you'll probably need some reinforcements for the containers, but that still seems easier to build than the false bottom. I think it would depend on what type of wood you're using and what size lumber.

To answer your original questions, if you really want to build a false bottom: drainage is probably not an issue because the false bottom won't be watertight, right? And a soil depth of 18" is probably fine for most perennials. You may want to select plants that are a zone hardier than your zone because they will freeze hard in the winter.

Karin,
Thanks so much for your input! I would love to see pictures of your yard as you work on it!

I Think you will have more problems than you'd care to have by building them that high and filling them with soil on top Just the water freezing in them in winter will cause the wood to bow and the bottom--well I don't know what would happen to it. I just don't think it's a good idea.

I have seen many modern homes with rectangular planting boxes. The trick is to have smooth sides. If you did build some that go to the ground you wouldn't have to fill them with soil all the way. I have a couple of large planters and only the top 2 feet is soil and that top 2 feet also has rigid styrofoam on the sides. In the bottom I have some gravel and broken up styrofoam cups and meat trays and anything styrofoam as filler. Your plants won't need any more than 2 feet of soil unless you are planting trees or shrubs. The gravel and styrofoam cups give good drainage to the planter

Below is a link to planters and how to build them. You might get some ideas for what you want

Here is a link that might be useful: Planter boxes

thanks everyone!!!

Those are useful photos dowling - amazing how helpful Google Image is for gathering ideas.

Logata, keep us posted. I'll be curious to hear what you wind up doing.

For our yard we are going with stone to build beds and paths. I am cringing at the price of the stone especially the crisp cut stone that looks so modern, but I will be doing the labor so that will be lots of fun!