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We bought the house next door to ours and tore it down, leaving us with a largish yard that runs alongside our house. The house next door had been a rental property, an old house split up into 8 apartments, which was often used to consume or manufacture drugs, including meth. Residents parked in the yard, changed the oil on their cars and motorcycles, and threw anything and everything onto the ground. At present, the yard has a highly-thatched covering of “grass.” I put “grass” in quotes because a lot of it are things that, when you pull them up, look like onions. But I don’t think they’re wild onions because they don’t smell like onions when I cut them open. They’re just small, hard, white bulblets underneath the grass. Underneath that is a layer of gravel and stone about 18" deep. The gravel/stone layer can’t be gotten through with a shovel, instead one has to use a mattock for about 15-20 minutes to get a 1'x1' hole. Underneath the gravel is very dense, thick clay and nothing but clay (the deepest hole I’ve dug was 5', and after the gravel it was clay all the way down).
I put a wood-panel fence around the yard. I’d like to cover the fence with some flowering vines, and plant some shrubs in the corners and around the yard, and some bulbs near the fence. It’s impossible with the present soil conditions – things get planted, they die. So I was thinking about borrowing an idea from container gardening. I thought I’d get a backhoe with an auger and put holes into the yard near the fence (after checking with utilities, of course) that are about (length x width x depth) 8' x 2' x 2' x 8' on stretches and 3' x 3' x 2' in corners. I’d line the sides of the holes with untreated 2x12's and then fill the holes with some good quality topsoil amended with some horse manure and sawdust. I’d plant the vines and shrubs and bulbs in those.
Do you think this would work? Is there anything else I should do? Do I have the right sizes for the 'boxes'? (We'd like to plant vigorous vines that are about 8-10' high and need to cover about 50' in two stretches of the fence. Any and all comments are welcome. Any advice on flowering or colorful vines, shrubs and bulbs would be great too. We’re up for some light pruning and occasional watering, but we’re not really gardeners. We’re in Zone 5. Thanks!
Thanks Cville. As to drainage, I don't know much about that subject. There's no standing water on the yard, even after the hardest rain. A quick melt of a large snowfall will leave the ground a bit squishy, but I put that down to freezing since it doesn't happen in the spring, summer or fall. Is that useful info?
OK, I did it. Dug a hole 1 foot diameter and 1 foot deep. Filled it with water to ground level. 3/4 of the water was gone in 19 minutes. The rest was gone within another 20 minutes, leaving just mud on the bottom. Bright sunny day, not overly humid, no rain in the past 4 days. Is that okay drainage?
Start planting your vines and see how you go, I think they will grow well, go ahead, you have to start somewhere. You will have all this time with good weather for your vines to get established and by fall their roots will be growing well to be ready for the cold weather.
Thanks, Cville and cristina!. I really appreciate the help. Do you think I could dispense with the wooden walls and just dig large holes, fill them with good quality soil, and plant in that?
Also, I'm planning on planting autumn clematis along a 50 foot fenceline. How far from the fenceline should I plant? How far apart should my seedlings be from each other? And do you have any advice on how to train the plants to go to the fence?
Again, I really appreciate the help. This is a fantastic place!
Sweet Autumn Clematis can be very weedy - the seeds will pop up everywhere around your yard. Great in the woods but can be a pest in your yard. If you insist though you could probably space them 3 to 6 feet apart. They will usually attach to most anything but a bird net or nylon net (used for beans or other climbing plants) draped over the fence will give them a head start. Plant close to the fence line - a foot should do but if you plant further away that will work as well. You shouldn't need large holes or much soil improvement unless you have really poor soil to begin with - they seem to be happy almost anywhere they can get a foothold. I grew sweet autumn clematis from seed at our last home and regretted it after a few years. The seeds popped up among other choice plants and I could never get the full root out or spray due to it being so close to better behaved perennials.
Do the holes for trees, you can always leave at the bottom of the holes pieces of wood if possible small chunks of branches of trees of different thickness that not only will help with water drainage but will improve your soil and feed the tree/plants, with smaller size plants I just leave them around, disguised with the mulch.
I do feel that we, gardeners, forgot the great value of mycorrhizal fungi the whitish fungus that we see in decaying, moist wood that are beneficial for plants, enabling them to extract nutrients and hold onto water in very difficult soil conditions,also the mycorrhizal will live with the plant, continuing a nutrient supply for its entire lifetime. In exchange the plant provides carbon and sugars to the fungi. Not unsurprisingly, 90% of all land plants employ this relationship to enhance their own root system’s capacity to deliver nutrients.
Did you want wooden walls to keep out oil spills and other chemicals? If you are not growing vegetables, I wouldn't worry about needing walls around your plants' roots.
When you said a 1' deep hole drained in 40 minutes, was that just a hole in the compacted gravel layer? Can you tell whether it was draining through or into the clay?
I see 2-3 scenarios.
#1 is easiest.
#2 is like "give up and fall back on #1.
#3 is more work for a bigger reward.
#1. Grow on top of the gravel and rely on that for excellent drainage. Ignore the deeper clay layer.
It's surprisingly possible to grow on top of, or in compacted rocks. Roots follow the crevices and find "enough" soil and nutrients in the cracks to grow. The excellent aeration is good for roots, and as long as there is "enough" water and nutrient retention, all is well.
If that's your situation, how about just piling any topsoil and compost that you buy on TOP of that gravel layer?
The you would have 4-8 inches of light, fluffy raised bed store-bought soil on top of excellent drainage that roots can infiltrate if the plants need it. Nutrients, organic matter and some clay will "leach" down into the gravel, enriching it, but probably not clogging it.
Four to 8 inches is "enough" for plants, especially if you aren't looking for lush growth or highly productive vegetable beds. Just keep feeding it a few inches of compost every year, and the gravel layer under it will gradually improve but probably not plug up.
You could make raised bed walls out of 8"x16"x 3/4" concrete pavers stood on end "the long way" so each paver gives you 18 linear inches of wall.
Or use sturdy solid-looking 12"x12"x 1" pavers and have a raised bed tall enough that you can add another 4" of compost any year you want.
Or treated wooden boards.
Or harvest some rocks and gravel, screen and wash them, and pour some concrete raised bed walls? Maybe paint them or work some texture into them.
Basically, garden "on top of the gravel" and ignore the underlying clay layer. It could be granite or solid concrete, you aren't relying on it.
"On top" could also mean "parallel to". Say you don't even want to raise up some good soil above the current grade. You could excavate some of the way down into the gravel, screen out the larger rocks, and mix purchased topsoil and compost with the sand and grit you just excavated. Wind up flush with the current soil surface, and have a bed 10-14" deep that still has enoguh gravel under and around it to drain well. Eventually the store-bought topsoil plus grit will become more fertile as you add compost over many many years.
2. Say the clay layer does NOT perk well. If you scrape away the gravel layer, and dig an 18" deep hole into the clay and it does NOT drain out in 2-12 hours, give up on that clay!
If the whole clay layer is impermeable, the third idea won't work because any part of the bed below the grade of the clay/gravel boundary would flood with rain and be unavailable to the root zone. It would go anaerobic or hypoxic periodically and kill any roots at that depth.
(If you have a slope or grade to work with, you COULD did a slit trench for drainage, from the deepest part of your bed to a deeper part of the yard, but now we're talking about engineering. Plop a raised bed on top of the gravel and pretend that the clay layer is solid granite.)
3. Say the the clay layer drains OK, even if it seems a little slow.
Now you have a really highly productive option that takes maximum advantage of the "problems" that the first scenario worked around and "made do" with.
Consider investing more work for a greater payoff. The backhoe will do most of the hard parts.
Heavy clay soil's problem is that it is "too much of a good thing" because it drains poorly. Otherwise, it retains water and acts as an ion-exchange buffer for every mineral that plants need to live. Clay grains are what root hairs and mycorrhizae wrap around and cherish.
Gardeners with sandy soil pray for a little clay!
The smaller grains that you scrape out of the gravel layer (sand, grit and fine gravel) will help maintain the open soil structure once you mix the clay with enough compost to lighten it.
Gardeners working to amend clay soil wish they had sand and grit nearby to add structure. You have both already, they just separated when the clay elluviated out of the gravel layer.
Scrape the gravel and crushed rock away from a long trench. Exppose the clay layer. A backhoe trumps a mattock.
Screen the bigger rocks and 1/2" gravel out. Maybe make paths with them. If the rocks are big enough, make walls.
But save the sand, grit and fine gravel from it to mix back into the clay layer.
Break up the clay maybe 12-16" deep with the backhoe, mixing in compost, sand, grit, gravel, lots of store-bought compost, leaves, paper, ground up vegetation, manure, coffee grounds ... anything that you would put into a compost heap is good this first year.
If you want to buy some topsoil and mix it in, you can. But look for rich, living, organic, sandy loam! Otherwise, the organic clay loam you just made will be better than what you bought, and the "dirt-yard topsoil" will cheapen the Number One soil you are creating.
Since the gravel layer was 16" deep, and you dug up 12-16" of clay, by the time the trench is back up above grade you will have amended that clay 50-50 or 60-40 with things that will improve the drainage. Since it always settles, and compost is always digested and subsides somewhat, you want the bed to be mounded up 6-12" above grade when done.
You have to keep feeding a lot of compost back to the trench for at least several years until the soil stabilizes in a high-organic, well-draining state. Maybe lay 4-6 inches extra compost on top of the bed each year. Some of that compost can be mulch that decomposes either fast or slow, as long as the soil gets an input of organic matter to sustain the living soil ecosystem you just created.
This adds soil structure and "lightness" and tilth as well as the organic matter that soil life feeds on (and the minerals that plants feed on, in cooperation with your rich clay).
After a few years, plant roots and soil organisms including fungi and worms will help maintain the soil structure and you'll need to add only enough compost yearly to keep the soil life fed. Say, 2-3 inches of compost per year.
The upside is that you will have created 3 FEET DEEP, super-rich, well-draining, A+ organic fertile soil.
Instead of treating the deep clay layer as a useless, dead object that at most threatens bad drainage, you've converted it into rich, organic, clay loam.
Instead of using the gravel layer as a passive mineral grid that roots can hopefully infiltrate in search of a few drops of water and grains of nourishment, you've incorporated it into a well-balanced soil and changed clay from an anaerobic problem to the best loam in the world.
You can probably guess which option appeals most to me! Butyou're the one who would have to do the work.
I hate to be a party-pooper, but I would actually go with option #3: dig and dig and dig... and then dig some more, all the while adding compost and shredded leaves/grass clippings to the mix. (I'm anal like that.) ;) Just imagine how beautiful and healthy that soil will be in the long run!! =)
>> dig and dig and dig... and then dig some more, all the while adding compost and shredded leaves/grass clippings to the mix.
Amen! That sound like bliss to me. Of course, it may not leave much time for planting PLANTS the first year ...
I dug up the "floor" of all my raised beds at least a little, and amended them at least a little, so the transition from "light fluffy soil" to "dead, solid clay" is gradual. That way, I get as much drainage as possible into the deeper clay layers.
Over years, nutrients and organics leach out of the raised bed and very gradually enrich the deeper layers.
BTW, I looked at the "soil triangle" recently, and it reminded me of something. To have stable loam that does not revert to clay and compact when the compost is all digested and not replaced, the mineral part of soil should be AT MOST 20% clay. You can have "clay loam" or "silty clay loam" with up to 40% clay.
So two parts of clay need to be mixed with 3 to 8 parts of grit, sand or silt ... or compost that you replenish every year.
I don't usually have that much compost, let alone crushed stone, so every year I am fighting against compaction and adding as much compost as I can.
By mixing compost and decomposed chunky mulch into the top 6-12", I get some of the fluffy value of a raised bed in addition to the deeper root zone of deeply amended clay.
I do love digging, and turning dead, anaerobic dirt into living, fertile soil.
Heh heh, yeah... he might end up with a lush patch of rich-smelling soil and nothing else - BUT! Next year it will be sooooo ready for plants! =)
When I started my "Big Bed", this is what I did. Skimmed off the top layer of grass, then dug and dug until I could dig no more.. then dug some more. ;) That stuff is wonderfully fluffy, but there certainly is clay in there as well. I still find some areas that didn't get dug-in as well as I'd have liked, but I just make sure to add lots of compost to the mix when I back-fill the plant, then "mulch" with compost too.