Hi,

I want to create a 25’ x 25' Permaculture mandala garden in my Philadelphia backyard (Zone 7a), but I have poor clay soil.

Since I want to improve the soil immediately, I don’t mind spending money to have a lot of new soil delivered and dumped on top of the clay.

Would this be appropriate?

If so, then what type of soil?:  Compost? mushrooms soil? or a Mix with top soil?
(Of course, each island of the mandala garden would have slightly different soil depending on what was planted there. For example, certain herbs prefer sandy, rocky alkaline soil.)

On the other hand, since I’m familiar with sheet-mulching & Hugelkultur, would it be best for long-term soil health h7 stability if I dug 12” down, put a weed barrier, then a layer of pebbles for drainage, then a layer of branches/small logs of apple & maple wood, then some old leaves and compost, then dump 6-12” of mixed soil on top ,then some much?

Any advice would be appreciated.

I lived near Pennypack Circle and King of Prussia for 14 years total many years ago.

I'd be afraid of buying topsoil in or near a metropolitan area, anywhere. I say that because they're looking to get rid of sanitary sewer solids that come out of the treatment plants. In a rural area I'd be comfortable buying farmers top soil, which is a rich black loam. Assuming the area you have doesn't contain a lot of construction scraps I'd build up the soil I have. As I remember there's a Midnight Mushroom plant near Philly so you should be able to buy mushroom manure which was used to grow mushrooms. It's been steamed a couple times which should help get rid of weed seeds. You could use peat from the big box store but if you can find it the mushroom manure will improve the soil as well, but give you more soil nourishment. Unless this has been used for a garden recently I'd guess the soil is highly acid and could use a bag or two of powdered lime from the big box store. It's stacked near the cement, sand and masonry supplies. Without  the lime you could probably grow acid loving plants like blueberries and strawberries. A soil test from Penn State would tell you how much lime to add, more precisely. If you buy manure in bags from the big box store they sell it by weight. So what you get is mostly water and sand. You want manure sold by the cubic yard in a pickup truck. A full yard, even two yards. I worked with a fellow in your area who told the story about his dad going every spring to a horse barn  for manure. He shoveled it into his trunk. Please don't let your kids tell that story for the next 60 years. Rent a UHaul for $20 plus milage.

For a 25x25' garden I'd turn an inch or two of the mushroom manure into the soil. I'd dig the whole thing twice. The second time will go much faster. With a shovel you don't have to do the whole thing before you start planting. You could plant early germinating crops like lettuce, radishes, and peas tomorrow. So as soon as you dig it you could start planting. Of course you could rent a rototiller. One of the bigger ones is a Troy Bilt model Horse which I bring up because from my experience it should have been called a Mule. Assuming you have rocks and maybe roots you'll find out why I say that. After you've run the Mule thru your garden, which you could do twice in different directions in one day, you probably won't need it again. A spade will do nicely.

If I were setting out tomato or Pepper seedlings, in May, I'd add another spade full or two of mushroom manure in as I plant them. I put my tomatoes in as deep as possible. I've put them in 8 inches or more if I have tall legging seedlings.

With mushroom manure you probably shouldn't plant root crops like potatoes, turnips, carrots or the radishes I mentioned above. Next year the root crops should be fine. But next year I'd add more mushroom manure, or composted grass clippings, and leafs, where I wasn't planting root crops. I only use grass clippings and leafs from my own property. I wouldn't use composted grass clippings that contain fertilizers and weed killers etc. and I don't know what's in someone else's mulch.

Good luck and let the kids help after the mule work.

I've dealt with heavy clay soil for 40 years, and I love the stuff.   So studying how clay soil actually works will help you understand it, and hopefully realize all of the benefits.

It is high in minerals, which makes food taste great.  It holds more moisture, so you don't have to water as often, plants will stress less.  

I've found the most important thing is to never let it be exposed to the sun, because that will dry it out, and then that's when it gets a bad reputation.

It does need some help in the drainage department, and granite sand it a good amendment.  

I prefer Trench Hugelkulture because I only have to haul the scraps and shovel the manure once.  Filling the clay back over the trench will allow worms to come up into it and really improve it.  

I like really thick grass/weed mulch from mowing the paths, so 8" over the clay, being added to when that shrinks down to 4" or 5", which might be in a couple of weeks, depending.  When mulch is that thick clay doesn't need as much water, except when you are starting new seeds or transplants.

I like doing transplants because it helps me see at the bench stage whether seeds are viable or not, and 3" plants have a better chance against rodents and snails.  When I put in transplants I dig a small hole, fill that half way with well rotted manure (which is over the hugel trench), then fill in around the transplant with my soil, then 2" of grass mulch, watching when to add more as it shrinks and exposes the soil, but not so much that the lower leaves of the transplant get covered.

If you have let your clay dry out before you begin to ready it for a garden, wet it down really well with a hose, put a tarp over all of it to keep it out of the sun, and leave it for half a day or overnight, then it will be ready to go in the morning.  Clay takes time to absorb the moisture, kind of like working with wheat flour when making bread.  But it's worth it.

About the trench, if you've got big branches, it helps to soak them in water with nitrogen in it until they are thoroughly soaked, overnight at least.  The easiest source of nitrogen is pee, but if that isn't to your liking, some organic fertilizer dissolved in water will do.   I like 3 foot wide beds, and 2 foot deep trenches, the lower foot depth for the branches, rotted manure, leaves, mowed grass, covered over with soil and watered in so there are no -- really, really no air pockets.  The top foot is clay fill over that with granite sand in it.  If granite isn't easy to find, there are other rock powders you can buy and add to the soil.  

If you've actually seen water ponding there in the winter, you might need to put perforated pipe along the bottom of the trench with the ends at a good angle downhill into another area so it really will drain.

If the soil is still too hard to dig after you've wetted and waited, dig out what you can, wet it again, and wait again.  I've got the stuff they made missions out of, and when it's wet enough it gives up.

Let's suppose you dug out a foot deep in your 25'x25' garden. It'd take 25 pickup loads to haul it. Haul it to where and then shovel it out of the truck. Sounds like about a month long task. Or an expensive job with a Catapiller loader, a triaxle truck, a crew of 4 or 5. You can't haul more than a cu yard of dirt in a pickup, because of the weight.

Or, you could rent a pickup, buy 4 yards of mushroom manure and haul it in two loads. Unload it in one day. It's light, it digs easy with a shovel. You load it into your wheelbarrow, push it to the back and dump it. Dump the next wheelbarrow in a different spot, spread it with a rake and start digging or rototilling it. Or you could hire a crew, get a mortgage on the house and wait for the crew to show up.

I'm picturing your 25x25' foot garden in NorthEast Philly. I can't imagine that garden space in South or North Philly. There was an apple discovered in West Philly on a corner, but that was in the 1800's. I can't picture it in West Philly either. I'm picturing a small city yard, the house in 2 or 3 feet higher than the street. I can't picture the back of the yards, it's been too many years. But I can't imagine a triaxle and that loader in that neighborhood. And I don't picture a wealth of dead tree limbs.

You want to plant a garden grow some veggies, maybe some flowers, put in a dwarf apple tree... maybe. Tomorrow  it'll be April, you could have been planting 3, or 4 weeks ago, your already late.

You could look for compost, I've never seen compost sold, it's something you do for your ownself. You don't need to finish the whole garden plot to start planting some seeds. You don't need a major project. You need a spade, a wheelbarrow, a bag of lime and something to improve the soil. You can buy peat, a 3 cu ft bag for $10, that's $90 a cu yard or buy the mushroom manure for $35 a yard, rent a pickup for $19.95 plus the mileage. On Monday evening you could haul a load and Tuesday morning haul another load. Get going, it's getting late in the season.

I'm trying to remember where there are horses in the Philadelphia area. I'm thinking the Main Line. I remember horses in Valley Forge Park, next to the covered bridge, but that was 40 years ago, it's probably a lot of houses by now. But if you can find horses they usually have a big pile that they give away for free. You'd need to scout it out before you rent the truck.

Good luck with your garden.

edit:

If you have grass where the garden will be, I'd turn over the sod into the clay, you need all the help you can get breaking up that clay. Some say to haul away the sod, that's where the weeds are. I knew someone who hauled all the top soil away, "that's where the weeds are". I ignore those ideas, the better the soil is the more weeds there are, the weeds will grow bigger, but so will the lettuce.

You don't haul out any soil, you put it back!   All of the soil is worthy stuff!!  Hugelkulture is about burying organic matter in the right proportions, then putting soil back over it so the worms come into the soil and improve it.   That's the "burying" aspect of it!

id buy quality bagged soil and make mounds with it. plant the mounds and cover all your area in at least 6in wood chips. add new fresh woodchips every spring to add to the building of your soil and keep out weeds. chip drop is your best friend! ;) been doing this in my yard for 10yrs. over time it builds a nice black soil on top of your clay soil. the plants deeper roots can still access the clay soil feeding your plants.

Hi Eric.

Just wondering what you ended up doing.

I have to say that the soil test is probably a good idea. In many cases of clay soil amendment, I have discovered that a calcium deficiency can be the cause of water impermeability. I like gypsum grit and powder for this. Forked in with organic matter, it opens up channels in the clay for water and air to pass through, carrying more grit, powder, and organic matter down into the clay, adding structure and giving the clay particles something other than themselves to cling to.

Honestly, I have literally tossed scraps of untreated drywall out onto clay soil in the fall, to find them largely broken up and incorporated in the spring, after the snow melt. The first time I did so was not too far from my compost area, and there was literally a line of improved soil between the two spots, what I assume to have been the worms' highway from Compost-town to Gypsumville.

I really hope you didn't truck anything away. That would have been a colossal waste, as some have tried to explain. And really, I think some gypsum, a few loads of that mushroom manure, and a good, thorough forking will fix everything.

Let us know how it's going, and good luck. Oh, and pictures would be amazing.

-CK

My soil is clay.

I improved it by mixing weeds and lawn clippings into the top 4 inches at about a 50-50 mix. I also added a little wood ash, some fertilizer, and whatever else looked good. Then I planted potatos because potatos do not need a fine seed bed. That was 4 months ago and that soil is looking DARNED good.

I hope that whatever you settled on has done well for you!

Anywhere in eastern cities you should be able to get a couple loads of free wood chips and leaves. Throw a mushroom slurry down or some stropharia spawn and plant some root crops in the spring or even this fall. You will have crazy good soil by next summer. And definitely some gypsum is good, I add it under the chips and the worms drag it down. Chris' idea with the drywall is super, wish I had thought of that. I also added some rock dust for aggregate size and calcium. most granite of basalt is going to help.