Organic Food Gardening

There are a number of different ways to make a new raised bed vegetable garden. Some work better on a larger scale, some depend on having soil present already, and some use more recycled materials.

Assuming you’ve already found a location with the needed sun and water access, the first question is, what’s already there?

In many cases, the answer will be “grass”, whether manicured lawn or shaggy rough turf. There are three main ways to turn a grass area into a raised bed, and I’ve tried all three.

1. Use machinery to till or plow the whole area, grass and all. This has the advantage that you can immediately use the soil that the grass was growing in, although you’ll often want to add amendments to improve it. Most books warn that the grass will grow back and be a pernicious weed, but I haven’t found this to be so when tilling up my very rough grass with a Mantis tiller. Yes, some grass does regrow, but if you pull out the obvious still-rooted clumps after tilling, and keep the bed weeded at least for the first year, I’ve found it to be easy to handle. Tilling through sod can be fairly easy, if slow, or close to impossible depending on your machine – some just won’t do it. The Mantis does a fine job but it’s slow. After tilling , you’ll need to remove weed and root clumps, add amendments, and shape the bed.
2. Skim off the turf and compost it, then dig the soil underneath by hand or using a machine. I found “skimming” to be physically demanding and time-consuming, and it took quite a lot of soil away with the grass. If you plan to do any considerable area, renting a turf-lifting machine would be a very good idea. Removing the turf and any weeds embedded in it does reduce the later weeding load, though. Digging the soil below can be done by single-digging, double-digging, or machine tilling. With this method you can usually incorporate amendments as you go rather than adding them afterward.
3. Use “lasagna gardening” or sheet composting methods to create beds on top of the existing soil/grass/weeds. This works especially well when your “soil” consists mostly of rocks and smaller rocks, as mine did in a previous garden. Six inches of leaves, grass clippings, sawdust, horse manure and a little soil on top grew an amazingly productive (but very weedy, from the horse manure) garden in its first year, as you can see from these pictures:
   
   Using this method to create a few small beds or one medium sized one is quite easy. When you start trying to create an entire large raised bed vegetable garden this way though, digging, hauling and spreading trailer-load after trailer-load of organic material gets to be a good deal of work. It’s also hard to find enough volume of material. A lasagna bed doesn’t need amendments added since it’s made of “amendments” in the first place! The weedier your starting area is, the more newspaper or cardboard you should use as the bottom layer of your bed.

If you have soil already, whether growing grass or weeds,  and you are physically capable of digging it, I recommend using it rather than layering on top UNLESS you have pernicious weeds like bindweed, Japanese knotweed, Canada thistle etc to deal with. In those cases, the lasagna method will give you a head start over the weeds.

What if your chosen area isn’t in grass?

If it’s already growing annual or perennial plants, apart from pernicious weeds, you can treat it the same as grass.

If you are dealing with brush, shrubs and small trees, first you may want to reconsider your choice of site. If you have no choice, you can cut down the brush to ground level and lasagna over it, or dig it up (roots and all) and dig or till. This is a LOT of work and if your site slopes you may have trouble with erosion unless you build terraces.

Some people may only have a paved area (concrete, asphalt or mortared paving blocks) to build a raised bed on top of. While this situation may seem disconcerting, it can be done. Your main concerns will be drainage and getting enough soil depth for good growth. First, can you break up the paving at all? Allowing water to drain through will help a lot. Maybe you can rent a jackhammer! Whether you can do that or not, you’ll need to allow weep holes in the downhill side of your bed surrounds, and several inches of drainage material (rock, pebbles,  sand etc) as the bottom layer of the bed. A layer of landscape cloth over top of the drainage layer will slow down the process of soil particles clogging the gaps. You can then lasagna-garden over the top, or add bought topsoil or compost. Either way you’ll need fairly high constructed sides to your bed.

You may wonder why I’ve only now mentioned bed sides. That’s because in many situations you won’t need them, but can simply slope the sides of your bed down to the ground around it. Constructed sides have pros and cons, as do un-contained beds:

It’s up to you whether you build sides or not. In many cases you can build beds without sides first, then add sides later if you want to.

To plant small seeds in your new bed, you’ll want to cultivate and rake the top to a fine seedbed. Otherwise, you can leave it fairly rough for large seeds or transplants. The ideal, if you have the time, is to plant a green manure or cover crop for the first season – but you can certainly grow food in a first-year bed.