Gravel and garden quality sand, though, aren’t as cheap as peat, which comes in large bales and serves some purpose. And the deal with SFG, @scualum is the quality of the soil in the box. Eg I successfully grow tomatoes in containers many would think are undersized. (But with attention to the type and its needs.) (My elevated box, btw, is only about 10" deep. The roots will spread.)
When I think about small space gardening, I think about my grandmother, who could grow anything, anywhere. But we’re not talking about that Victory Garden generation. I’m wondering how competent OP’s users will be, to know the adjustments to make or if they need some set up that’s relatively guaranteed to produce.
@lookingforward - I’ve followed the Square Foot philosophy for years in my raised beds - I just find that you need deep soil for tomatoes or they don’t do well. Sure they can spread horizontally - but then they are competing with the plants nearby. Or you can plant determinate varieties - but then you end up with a smaller crop. Will the users of these beds know that they have to stick to certain varieties?
With tomatoes I just plant 'em deep, encourage them to grow deep, and eat real tomatoes all summer and fall long.
@scualum:
I haven’t had the problem with my container beds, they are a foot deep, and I plant 4/box and get a ton of tomatoes every year. There is enough space vertically and horizontally with the roots, and I get tall, healthy plants no different than when I did ground gardening. It is very important to have good soil in the boxes, when I originally tried them I had regular old dirt in them and it didn’t work. I have planted everything from plums, to Jersey Heirloom beefs, to various hybrid and heirloom tomatoes, and all have done well.
I guess we have had different experiences.
We met with a representative today, and learned that we have generated lots of excitement with our announcement to do this project for them. They have a very active garden club. Turns out this is an independent living facility, not assisted living. The residents are in varying degrees of health, of course, but sounds like we will have an audience for the work as it gets done and I imagine a lot of helpful advice from these resident gardeners.
Keep any advice coming, I am reading as I can and trying to relate your words to our project. I will be traveling and won’t respond promptly for the next week, but will try to at least read posts as I get the chance.
You can also make a “salad table box” for the residents. They are shallow raised tables that can be put together quickly and used to grow salad greens and other things with shallow roots. You can use them to supplement the deeper raised beds, or to satisfy the green thumbs while your deep raised beds are being built. Or both.
Here’s a video of how to get started. There are other tutorials and diagrams of building the tables themselves.
You could also easily make some tables that are a good height for wheelchairs.
https://www.youtube.com/watch?v=jKHd24rq7nw
You know you need untreated wood for veggies, right?
The other thing about gravel and sand is they promote drainage. Peat promotes retention. In a simple raised bed (where the growing bed touches ground soil,) fine. But if you do build elevated (one way or another,) you need to consider retention, since it dries out faster.
This is what I was trying to describe, with the false bottom, not the drainage, but how you can spare some of the soil needed. http://www.familyhandyman.com/landscaping/planters/build-your-own-self-watering-planter/view-all
Love the salad table idea. Some herbs could probably do well the same way.
So it seems your choices are:
- Partner with your city, county or a local landscaper/gardening store or somewhere to get donations of topsoil at free or reduced costs. Our community garden has an area set aside - basically a mini-mountain - one for topsoil, one for mulch and a WEE little one for peat as a result of compost.
- Build shorter beds - but I understand the desire for taller beds for easier access so…
- Put 12-15 inch beds on legs of some sort. More work initially to build, but less fill needed over time.
- Build 30 inches tall, but smaller bed overall - maybe 4 x 4. Small, but enough for garderners to have something to take care of. That’s still 16 “squares” for planting.