Requesting raised bed design suggestions

[u/Snookaboom]

Hi everyone,

I’m an ecopsychologist, naturalist, native plant person, and I would say permaculture adjacent, though I haven’t been able to complete the PDC. I am very interested in local community and food resilience.

I live in Southern CA USA, Los Angeles County. The soil here is predominantly clay. My yard is about 50’x25’ and has trees lining one side (avocado, plum, and soon a persimmon), and a garage along the other side. The short sides have a fence (with more trees) and a patio. The side by the garage is where the raised beds have been. It reliably gets the most sun even during the winter.

My house is over 100 years old. Overall that’s a good thing because there was no previous industrial development on the land. However, due to the lead paint that was used on old houses, my soil has some lead in it. Thankfully no other concerns were detected. I used a professional soil lab (Wallace Labs, El Segundo CA).

I last tested in 2020 and since then have moved to raised beds, and some mitigation with phosphorous, as well as sunflowers and scented geraniums. Of course also mulch and chop-and-drop of clean plant material. I will need to re-test soon. I have read that lead particles tend to go 3-5’ down, but in clay soils they are more concentrated in the 12-18” nearest the surface.

My gardens are often trashed/invaded by raccoons (digging up new plants looking for grubs), cats (love to poop in the beds), and squirrels (who do any number of destructive things in there, usually burying peanuts). The only thing that has kept them out is sprinkling cayenne powder every day or two, which becomes expensive and time consuming.

My tall galvanized raised beds are starting to rust; and I have not been happy with the design anyway. The beds are too tall, and the metal can get too hot, especially with the heat waves we’re getting now. The soil gets too dry and turns into dirt; and the bed is so tall the nutrients tend to leach downwards with watering. It’s not held by the earth.

I’d like to return to an in ground bed. Soil quality would be better, and I wouldn’t have to worry about raised beds.

So my current plan is:

* deconstruct current beds, set aside the soil on some tarps
* dig out about 3’ of native soil, in a rectangular shape roughly where the beds are now
* backfill the hole with the organic soil from my current beds and a bunch of compost; and mulch/hay covering
* use a brick and board system to designate a border.
* consider using some sort of fencing to keep animals out.

Potential problems with this design:
* Lead doesn’t tend to leach upwards, but would it leach sideways, from the edges?
* How to keep the darn animals out?

Am I missing anything that you can see?

Thank you in advance for your thoughts!

[u/GrandStocks9]

digging out 3 feet of clay sounds like a proper workout, my back hurts just reading it. but if you got the lead mostly in that top 12-18 inches then removing all that makes sense, just hope your new soil dont get contaminated from the sides over time. maybe line the edges with something like landscape fabric or cardboard to slow any sideways movement

for the critters, cayenne gets old fast. a physical barrier is the only thing that stopped the cats in my yard, i put chicken wire flat on the soil around plants and they hate walking on it. squirrels are a different beast entirely, they just laugh at everything

[u/Snookaboom → u/GrandStocks9]

Thank you! 🙏

[u/YsaboNyx]

Since you're already digging out the beds, I'd also line them with hardware cloth/gopher wire before refilling to prevent critters that might dig down and come up from underneath.

Fencing really helps. I found that buying old dog kennel set-ups on marketplace/craigslist was an easy and economical way to get a perimeter garden fence up. They come with all the hardware and don't require you to set posts.

[u/Snookaboom → u/YsaboNyx]

We don’t have any digging critters in my area of the city—they’ve all been extirpated. 😢

Thank you for your thoughts and support!!

[u/PuzzleheadedDraft480]

Reading some studies gives me the understanding of your "some" lead in soil, most is bound up in roots. Lead impairs plant function in stem/fruit tissue so the plant is invested in mitigating that absorbtion.

I would simply plant as you normally would, and not compost those plants at end of season - the lead roots get thrown out.

[u/Snookaboom → u/PuzzleheadedDraft480]

Hmmm, that’s an interesting idea: using the garden roots themselves for bio remediation. You really got me thinking about that. Thank you!

[u/paratethys]

sorry to double post but I keep thinking about what the heck I'd do in your situation, and some options for the problems you're facing with the galvanized beds have come to mind.

I'm actually wondering if placement is part of the problem you're having with the current raised beds. You know how any advice that one person needs, someone else in the world probably needs the opposite of that advice? well, I'm kinda wondering if "put the beds in the place that gets the most sun" might not actually be the best solution in your case. If they're on a south or west exposure, that might be too much heat. I would try a couple containers on the north or east side of the building -- if you can avoid direct sun on the sides of the bed during the heat of the day (usually mid to late afternoon), it'll help address the soil-cooking issues that you describe.

My experience from large black nursery pots, which probably transfers reasonably well to metal beds due to the similar thermodynamics, is that wrapping a sheet of cardboard loosely around the sunny side of a bed can work wonders in helping all the soil in it stay at reasonable soil temperatures when it would otherwise get too hot. Or hanging some burlap over it, or propping up a cut-in-half pallet by it, or whatever. Anything that keeps the direct sun off the surface that's touching the soil makes a real difference.

The larger the raised bed, the less it acts like a flower pot and the more it acts like a scale model of the full soil ecosystem. If your galvanized beds are actually pieces-of-bed that are fastened together, consider whether you could rearrange those pieces to make a larger pocket of isolated soil. for instance if you have 2 raised beds, each with 4' sides and 1' ends, you could reassemble the pieces into a single 4'x4' bed.

Also... this is gonna sound crazy, but you can build a false water table underneath a deep container of soil. The MVP is a kiddie pool, with several deep pots of soil sitting in it. You want most of the soil above the water level in the pool, and I like putting a bunch of biomass (wood, straw, ferns, whatever) in the very bottom of the pots so the soil has a harder time washing out through the holes. The goal is to have the soil you're actually using to grow in be fully above the water level, of course. You can experiment with leaving the water vessel mostly empty, and just letting it catch the runoff water from when you water the containers in it, then the pots can wick the standing water back up into the soil or it can evaporate leaving whatever it leached out. once in awhile you take the silt and stuff that builds up in the pool and put it back on the tops of the pots, returning everything that tried to leach out.

or if you want to keep a higher water level in the vessel, you can find a native azolla or duckweed or whatever makes you happy, and grow it on the exposed water surface around your pots. then when it covers the surface of the water, scoop about 1/3 of it either directly into your pots or into your compost. another perk to including water-surface plants in a garden is that they give pollinators a spot to stand and safely drink water, rather than drowning like they tend to if there's nothing on the surface.

these ideas may not be directly applicable to your situation, but i think they're characteristic of a couple angles that you hadn't mentioned having already considered :)

[u/Snookaboom → u/paratethys]

Hey there, thank you so very much for your kind support and advice. Really don’t even think about apologizing. I’m genuinely touched by the level of support I’ve gotten here.

I have so much going on this week. I’m gonna have to really return to this post and all of the comments, and digest it over the weekend. So I’ll probably post some more responses then.

[u/paratethys]

Not sure on lead, but I do have thoughts on keeping the animals out.

Find your local pet-focused thrift stores, and your buy-nothing type groups. Any material that could keep a given animal in, will also keep them out. The absolute easiest option is an XL or XXL folding wire dog crate that's lost the plastic tray that goes in the bottom. Once the plastic tray is gone, those crates aren't good for their intended use, because the wires on the bottom are spaced too far apart. But if you just put the crate right on top of a section of the garden bed -- nestle the bottom of it down into your soil, optionally secure it to the bed edges or pin it down with tent stakes or just run a couple old untreated 2x4s along the bottom so they go over the crate's bottom wires and through the holes and along the sides... or put some rocks/bricks inside in the bottom of it to weigh it down... basically just improvise with the materials you have to make it too hard for any of your problem critters to move the crate. Then you use the doors of the crate to easily access the critter-free microclimate inside it.

The folding metal fences used to contain pet rabbits or small dogs can also be good for building critter exclusion with, as they usually come with doors of some sort also, but you have to use pliers a bit more to remove a couple panels to make a roof out of. You can use wire to attach the panels to each other, or zip ties, or biodegradeable string and just replace the string when it eventually rots off.

I'd strongly recommend excluding critters only from individual beds, rather than trying to keep them off the whole site. Then if one exclusion experiment fails, it doesn't let them trash everything... and if there's a bit of garden bed left exposed around your exclusion cages, the critters tend to focus their efforts there rather than hassling as much to break in.

Or you can look up how to make a DIY plant cloche from fence material, though those take some clever wirework to add a door on for easy access to the plants inside.

If the squirrels or little birds are determined enough to squeeze uncomfortably through the bars of your critter excluders, you can escalate to covering them in a layer of hardware cloth. If you'd also like to exclude most bugs -- not usually desirable, but maybe you're working on something where you want to fully control pollination -- you could instead use a layer of window screen.

If the raccoons figure out how to work the gates of your critter excluders, try a locking carabiner to secure them shut. If they figure that out, escalate to dollar store padlocks -- keyed is probably best, dial-type combination lock second-best, and the combination type with 3 or 4 wheels of numbers probably the worst, in terms of whether I'd personally be able to get them open if I had raccoon hands and too much free time.