We’ve all been there, out of room and eager to expand the garden. That sod starts to look like the enemy and eventually the only question is, do you smother the grass with whatever you can find, or do you buy ready-to-go soil and get your seedlings in the ground asap?
Build vs. Buy, a classic garden soil dilemma. I’ve opted for both methods, and both have their advantages and disadvantages.
Build Your Soil
Building your soil means taking what you have or can get locally – your native dirt, kitchen trimmings, non-toxic sawdust, appropriate animal waste, sand, bark, yard waste and the like – combining it appropriately, and giving it enough time to break down into something your plants will be happy to grow in. I’ve done this.
“Oh, wait!” I can hear you say, “you mean composting!”
Well, yeah, basically. I “build” soil the same way I make slow, half-ass compost, I just don’t aim for quite as rich a finished product.
Most of my soil building has happened as a happy side-effect of smothering lawn.
I spent much of this past week smothering (more) grass with cardboard and burlap and woodchips. I’ve done this particular smother-dance so many times that I know what’s going to happen.
For the first week or so, everything will be puffy. Then a few good rains will saturate the cardboard and help the woodchips knit together into a more solid mulch.
After about a month, the cardboard will start to break down. Beetles and worms will come from wherever they live to chomp down on the decaying cardboard. Yum, carbon buffet!
After several months, scraping away the top layer of chips will reveal white threads of mycelium woven throughout the strata of the woodchips. The cardboard will still be recognizable, but it will be soft and tattered. The grass underneath will be dead. A whole world of teeny life will now call the mulch home. Worms will party like it’s 1999. Millipedes will curl into tight little armored C’s when disturbed. Sow bugs and little grey slugs and yet more beetles will find a habitat well suited to their needs.
Depending on the time of year, within about six or twelve months mushrooms will start popping up out of the chips. There will be great strange flushes of mushrooms that will take over whole sections of the mulch in what seems like a few hours. I’ll walk through kicking them over and smashing them into the chips because, though I recognize the critical importance of fungi in soil building, I remain in constant terror of my preschooler popping a few unidentified and possibly toxic mushrooms into his mouth when I have my eyes elsewhere.
A bit more time – another nine or twelve months (best to just ignore this process entirely if you are an impatient person) and only the top layer of woodchips will still look like woodchips. The lower layers will be a rich, dark soil dotted with the occasional bit of un-broken-down wood. There will still be striations in the soil – the area that was sod may be distinguishable as a particularly dark layer of soil. The cardboard layer may remain for a while longer as a tan line – almost a goo.
This is DIY Soil. Start to finish, good soil building this way takes a year or two in my climate. Hands on time is however long it takes to spread cardboard and woodchips and any other compostables you might want to add, and then nature just takes its course. This is a set-it-and-forget-it technique.
- Control over components of your soil mix
- Recycles waste-stream compostables within your yard and community
- Easily practiced with lasagna and hugelkultur style gardening
- Potential for warmer soil through action of composting-in-place
- May require time and labor to locate appropriate low-cost materials (like manure) and transport them to your site.
- May require research into the best soil components for your growing conditions.
- Soil will not look as uniform as a purchased vegetable growing blend.
- Nitrogen tie-up during break down, particularly for high-carbon mulches (straw, woodchips, etc.)
- Imbalance of carbon to nitrogen ratio may result in soil nutrient deficiencies or pH that needs modification.
If you are cheap and patient, natural soil building is the garden method for you! Pile it on and sit back – gorgeous soil will be yours, eventually. And this isn’t to say you can’t plant your DIY soil before it matures into a more broken-down, chocolate-cake textured tilth. Just don’t expect your best results in the first year.
Something I will often do in a new compost-in-place based bed is dig planting holes in the mess of straw and woodchips that makes up the top layers of a new bed and fill those holes with finely screened compost or commercial planting mix. I will then transplant or seed into those pockets of “perfect” soil. This gives the seedling the best possible start and by the time roots reach the loose pile of organic matter that is the rest of the bed, the plant is mature enough to start mining that mix for nutrients and moisture and contributing to the positive breakdown of the bed.
Everyone and their Grandmother has some “named” version of deep-mulch composting in place, which is all this really is. Check out any of the following to find the method that works best for you, your natural materials and your climactic area.
- Lasagna Gardening: original method and simplified method.
- Hugelkultur: overview article and my experiments with hugelkultur
- No Till Gardening: Ruth Stout did it naked. OSU prefers it with black plastic.
- Back to Eden Gardening: Watch the original free film and prepare for woodchips and Bible quotes. I love this film. Christian gardeners may find it beyond inspiring. Deep-mulching non-Christians who aren’t bothered by the Evangelical overtones will find much to love as well.
Buy Your Soil
There is another way to get vegetable growing soil. You can just buy it. Fork over some cash and wait for a guy with a dump truck show up and deposit 2 (or 18) cubic yards of finished growing mix right in your driveway. I’ve gone this route too, and there is nothing wrong with it.
In fact, though buying your soil has less DIY cred than the hands-on artisan creation of tilth, I once ran the numbers and came to the conclusion that, by buying a few cubic yards of ready-to-plant soil, I could start a new section of garden a season earlier and thereby grow enough vegetables to offset the investment in the initial dirt. (P.S. – You want someone to help you justify spending $300 on dirt I am always your girl.)
The timeline looks like this: call compost company, give them your credit card, set up a delivery date. Spend a few hours hauling your soil mix to your garden or shoveling it into raised beds. Wait a few days for your new soil mix to cool down (it often arrives steaming hot from residual composting activity). Plant. Instead of a year or two for really nice tilth you wait only as long as it takes for your credit card to be authorized.
Premade garden soil also plays very well with raised beds. Urban gardeners like me like our raised beds, and for good reason – they are fast to set up, easy to work, and allow us to sidestep issues of drainage, compaction and native soil contamination. As it so happens, one cubic yard of soil just about perfectly fills on 4′x8′ raised bed ten-inches deep. Those kind of calculations are simple. Simple is nice.
If you want a garden and you want it now, buying your soil gives immediate gratification.
- Immediate, no-wait finished soil.
- Consistent – a supplier’s “vegetable blend” mix is likely to be the same from batch to batch.
- Unlikely to transmit pathogens. A high-quality, professionally made hot composting process should destroy spores, viruses and other plant pathogens.
- Depending on your location, purchasing through reputable soil companies and composters may support urban composting and waste reduction projects. For example, Seattle’s largest compost company, Cedar Grove, is active in working with restaurants to reclaim food waste for composting.
- Components of soil mix may be objectionable. Check sources of compost before you buy – is sewage sludge a component? Is the compost component likely to contain residual herbicides or pesticides? Is the composting process hot enough to kill invasive weed seeds and rhizomes?
- Sterile. The same hot composting process which should kill pathogens will also kill beneficial soil microbes. Your purchased soil is, at best, a blank slate.
- Will probably need supplemental fertility.
- Quality is highly dependent upon individual blend from soil provider. Do not assume one provider’s “planting mix” is equivalent to another’s.
Before investing your hard earned cash in ready-to-go soil, get a sample. I cannot emphasize this enough. I once bought 18 cubic yards of planting mix based on the description of the mix from the owner of the company who was selling it. Big mistake. Huge. The few dollars a yard I saved over higher quality planting mix were quickly spent on supplemental compost to amend the crappy 18 cubic yards I came to possess.
A good ready-to-go vegetable planting mix should be a blend of compost, loam, sand and aged manures. Mixes will vary by manufacturer and the ideal mix will change based on your location but should always be well mixed and screened to 1/2-inch or smaller. Mixes for a vegetable garden should typically be about 20% organic matter and free-draining. Check your sample: a good garden soil is dark, crumbly and moisture-retentive.
In two sentences I have just invoked the phrases “moisture-retentive” and “free-draining.” I know, it sounds like an impossibility designed to drive gardeners crazy, but really it’s not. It’s a strange miracle of compost that it can be both moisture-retentive and free-draining at the same time. I know of nothing else that manages to be so charming in its bipolarity.
Either way, you may need supplemental fertility or pH correction. This isn’t necessarily a failure on the part of your soil building or your soil buying. Typically, an immature compost-in-place bed is quite acidic. This is normal, it’s a part of the composting process itself, actually.
According to Cornell University, ”During the initial stages of decomposition, organic acids are formed. The acidic conditions are favorable for growth of fungi and breakdown of lignin and cellulose. As composting proceeds, the organic acids become neutralized, and mature compost generally has a pH between 6 and 8.”
Even your “finished” planting mix probably won’t be perfect right out of the gate. My experience with purchased soil is that it lacks background nutrients – a hot composting process tends to burn through nitrogen a bit more than a cooler, slower composting process.
In the Pacific Northwest, where acidic conifer debris combines with nine months a year of rain that leaches alkaline nutrients from the soil, you’ve got the perfect storm for acidic soil. Clemson University says, “Rainfall affects soil pH. Water passing through the soil leaches basic cations such as calcium (Ca2+), magnesium (Mg2+), and potassium (K+) into drainage water. These basic cations are replaced by acidic cations such as aluminum (Al3+) and hydrogen (H+). For this reason, soils formed under high rainfall conditions are more acid than those formed under arid conditions.”
I use Steve Soloman’s recipe for complete organic fertilizer (optimized for the Pacific Northwest – other areas may need a different mix). You can find it here. But before committing to a regime of haphazard soil amending, the best thing to do is order soil test from a reputable university or extension service lab. The lab will make recommendations for the appropriate soil amendments based on your soil’s needs.
- The Complete Compost Gardening Guide. My favorite composting book.
- Growing Vegetables West of The Cascades by Steve Solomon. The gardening Bible for Maritime Northwest gardeners.
- Organic Gardener’s Composting by Steve Solomon. Free digital book.
- WSU Extension Horticultural Myths (PDFs): Compost and Nutrient Overload
What’s your choice. Do you build your soil, buy it, or both?