Gardeners of MeFi, help! Raised bed or not for vegetable garden?

April 2, 2017 12:42 PM

We are preparing to put a vegetable garden in our new house. Dimensions will be approximately 20 x 40'. I'm sure there's a better place to ask this, but I can't figure out where, and we need to get going on the project! Do you think it would be better to till the soil and supplement, or put in raised beds?

We live in a ledgy area, our soil has more clay than other soils I've encountered, and while our lawn seems dry, if we dig any sort of hole in it it tends to accumulate standing water. We'd like to put in a large vegetable garden, and I can't figure out whether we should do a few larger raised beds, or till the area and supplement with a good amount of compost and loam. Is there some rule of thumb for how to decide? Is there a soil test I should do that would be helpful? I think raised beds with new compost and loam mixture would be more expensive, but we can swing the cost if it would result in a more productive garden.

posted by zibra to Home & Garden (16 answers total)

I also live in an area with very clay-y soil and I'm taking a break from building four large raised bed boxes right now. It's easier to garden and clay soil is the worst to try and grow in.
posted by Marinara at 12:47 PM on April 2, 2017 [2 favorites]

How long term is this plan and how much do you want to spend (time and money)? Beds will take years to 'pay off', planting in the ground gets you going for much less, and will give you more square feet.

I would lean more toward traditional gardening for that size plot. Less work and money up front, gets better and better over the years as you build up good organic matter in the soil. Any raised bed will need repair and replacement, maybe in as few as 5 years depending on how much you spend, but a good garden plot just gets better with proper use and care.

You can always put in a raised bed or two next year for your most sensitive and high maintenance stuff, or for the showy stuff, etc. There are good reasons why vegetable gardens are not traditionally made by having rows of large raised beds- it's not the most efficient use of money and time for food. If you have lots of money and less time, the calculus may change for you.

Whatever you do, start composting religiously today if you aren't already doing so.
posted by SaltySalticid at 12:58 PM on April 2, 2017 [1 favorite]

Our garden sits on a heavy boulder clay - you can pretty much cut it out of the ground and it's ready to throw pots.

We put in raised beds. I borrowed a turf cutter to remove the top inch or two of turf and soil, and then composted the cut turf for 2 years and it's now part of the soil in the beds. The beds are about 10 inches deep, and we used a couple of tonnes of topsoil from an organic farm nearby to get things started. Each year we supplement the beds with all of our composted waste, including the waste from the beds themselves, and add some well-rotted manure. All of this means that it's not going to pay us back in food for a number of years.

The main thing with clay soil is that you just need to mix sufficient organic matter into it, and that, with the help of worms and roots, will eventually get you lovely soil. You can do that with or without raised beds (which, as SaltySalticid says, you can add later).
posted by pipeski at 1:06 PM on April 2, 2017 [1 favorite]

In my last large garden we used a bed system but they were not raised. We marked them out and turned some
of the topsoil from the "paths" onto the bed area. We only rototilled the first year and left the soil in the beds
undisturbed after that. You will save on amendments if you only apply them to the beds and if you don't walk on them they won't get compacted. The paths can be a nuisance to weed so we experimented. I think the deep layer of shredded leaves worked better than the clover but has to be renewed occasionally. Four feet is the widest bed we found convenient to work on and we made every other path wide enough for a wheel barrow. This was on sandy soil but I think the basic layout would work on other types.
posted by Botanizer at 1:22 PM on April 2, 2017 [1 favorite]

There's clay and then there's clay. But in general, I'd do raised beds only if you're worried about, e.g., lead contamination in your soils.
posted by salvia at 1:42 PM on April 2, 2017 [2 favorites]

800 square feet x the height of your bed = a lot of soil, probably more than you anticipate.
not saying you shouldn't go raised bed, but I'm not sure what your budget is, and you might be better off spending your money on other things!

whatever you decide, good luck and enjoy your garden!
posted by bitteroldman at 1:50 PM on April 2, 2017

I would make planting rows with hay bales, pile on the best soil I could find right on top use drip irrigation seed the ridge , in between the rows I would spread gypsum , next year alternate rows with new bales and more gypsum .
posted by hortense at 2:17 PM on April 2, 2017 [1 favorite]

Raised beds are an investment. But clay soil is the worst. You can grow certain crops, but they'll generally give less yield for more work. I'd do a drainage test on your soil to see how bad it is. Less than 1" an hour and you're in danger territory - beyond water issues, wet soil lends itself to a variety of fungal diseases. And veggies can be pretty delicate.

Clay is workable, though! Tilling is awful for soil microbiology, but if you're limit it to once every 3-4 years you can probably slide by. Leaf compost and perlite (in a 3/1 ratio) is a good combo for better drainage. You'll want 4" of amendment per 6" of soil. Also consider starting a yard waste compost pile so that, in the future, you can use your own instead of having to buy. For a 20'x40' area, you'd need ~200cuft/7.5cuyd of compost and ~67 cuft/2.5cuyd perlite (relevant calc). Where I live, that's ~$400 for the perlite and $225 for the compost - YMMV. Avoid sand and gypsum; under the right conditions, they can basically turn your soil to cement.

With raised bed, they're most effective at 4' wide - easy to reach to the middle from both sides - with 2' of path between beds. 12" is a good depth for most veggies, so you're probably looking at 2"x12"x10' dimensional lumber for your 20'x40' area. Three boards per bed is ~$36 plus 40cuft/1.5cuyd of basic soil at ~$45 per bed - again, YMMV. But if you're even in the ballpark of the estimate, 10 raised beds would cost ~$800 in material and give you less growing square footage.

It's hard to say whether either would be more productive. You have no idea what the base yield of your soil is right now, and there's plenty of other factors you can't control - just choose whichever works best for you, and stick with it!

PS: Whichever you choose, ROTATE YOUR CROPS.
posted by givennamesurname at 2:49 PM on April 2, 2017 [5 favorites]

I really like raised beds for a little bit of extra pest and weed control, and even just a 4-6" raise means you have something to attach hardware to for building PVC trellises and frost hoops. I also think it looks nicer.
posted by Lyn Never at 3:49 PM on April 2, 2017

I've got superduper clay soil and I'm also a cheapskate. I basically used the lasagne method without creating actual boxes or edges for the beds. Just dumped layers of cardboard, compost, soil, etc on top of the grass where I wanted beds. In mounds. Then I filled in the gaps between the new beds with wood chips. A load of woodchips, top soil and mushroom compost, delivered from a nearby garden centre, cost around $150 and covered my whole grass area (six large beds)

It's two years on now and I'm thinking about edging the beds, but they have sunk a bit and don't look raised any more. And digging down there are a ton of worms and no sign of clay until you get really deep.
posted by lollusc at 4:04 PM on April 2, 2017 [3 favorites]

Before you rule out gypsum watch Rick show you how break up clay soil.
posted by hortense at 4:46 PM on April 2, 2017

Depends on how anal retentive you are? If your soil needs a lot of tilling and amending, you're going to be spending money and doing a lot o work either which way. But I've always done raised beds because if I'm going to be busting sod and shoveling and tilling and getting compost and stuff delivered, I might as well get square edges out of it. (Also I live in Pittsburgh so god only knows what kind of heavy metals are in my soil.) Raised beds also makes it easier to do a square foot gardening method. And I've always had this evil Bermuda grass in my yards that just invades everything that isn't separated from the yard by a physical barrier.

I'm building some beds right now (we moved at the end of last summer so I'm starting from zero again) and am using cedar fence pickets and untreated 2x4s.
posted by soren_lorensen at 6:08 PM on April 2, 2017

You might think about cheaper raised beds using straw bales. Its not for everyone though so you should look into it further if you are not familiar with straw bale gardening. Also Colorado State University has a soil testing lab that is inexpensive. They can tell you about what your soil really needs if you are going to try to ammend it.
posted by WalkerWestridge at 8:05 PM on April 2, 2017

You don't necessarily need sides for your raised beds -- you can have some truckloads of soil brought in and make raised beds without sides. This would probably be the easiest, most productive option for that size of plot. The plants won't thrive in heavy clay soil, building so many raised beds to fill that space would be labor intensive.
posted by Ostara at 8:41 PM on April 2, 2017

Reasons to garden with raised beds: no tilling, soil doesn't get compacted, warms up earlier in spring, cools off later in fall, easier to weed.

Reasons not to garden with raised beds? I really can't think of any.

Source: 20+ years of gardening experience.
posted by acridrabbit at 2:09 PM on April 3, 2017

we built raised beds out of lumber for a space about that size; they'll cut it for you at Home Depot or wherever, and then it was just a weekend driving screws into square corners. (Ours are four feet wide and variably long, to make a pretty pattern in the space.) Our soil is pretty good, but raised beds are just so much easier. I've also gardened in an edgeless raised bed at a community garden I managed for a while. It was fine, but I prefer the wooden edges. Wooden raised beds also make it easier to put up anti-bunny fencing.

(For the paths in between we used play sand, which keeps weeds down very well and which lets our kids use the garden paths as their sandbox ... dual use of space and keeps them from digging in the planting beds! Regular sand also works but play sand is a lot nicer to walk on.)

Call around to a few "sand and gravel" type places and see if they'll deliver you half a dumptruck of soil and compost. (You can usually order by weight or cubic feet, they're very helpful in helping you figure it out.) You'll pay more than a commercial client buying six truckloads, but a LOT LESS than buying it by the sack at the garden center. They'll dump it either in your yard or in your driveway, depending on where they can get the truck, so just be prepared and have it done on like a Friday afternoon when your cars are moved to the street so you can spend all weekend wheelbarrowing it to where it needs to go! (In my experience friends are willing to help with this kind of project for an afternoon if you treat them to dinner. Like they won't come be your free labor all weekend, but they'll put in three hours helping you move a bunch at once.)
posted by Eyebrows McGee at 3:50 PM on April 3, 2017