Green Man Publishing

Growing beds

The past 30 years have seen a big change in vegetable gardening in this country, with wide (often raised) beds replacing the traditional row cropping in many cases. This might seem like something new, but very little is really new in gardening (except when new materials lead to the development of new techniques). If something works to make gardening more productive, you can be sure it was  used and refined a long time ago, when growing your own food was a serious business (though it may have been forgotten in the interim). Wide beds are actually a very old method of growing plants and predate row cropping, simply because they work so well.

Intensive growing beds have a number of advantages over the traditional rows.

Advantages

  • A wide bed may contain several rows of plants, but only requires one path, whereas a row garden has a path between each row. Hence using wide beds means less land is wasted on paths which increases productivity per square foot. This makes them the most productive way to grow food in small gardens.
  • The beds are never walked on so compaction is kept to a minimum. Plant roots can move easily throughout the loose, well-aerated and fertile soil.
  • Water and fertilizers are used more efficiently because they are only applied to the soil in the growing beds, none is wasted on the paths (and growing weeds).
  • The high level of fertilization on these beds means the plants can be spaced closer together, giving higher yields per square foot of ground.
  • Wide beds work best for small plants that can be spaced closely together, to give continuous cover. The closely spaced plants quickly form a dense canopy of foliage across the bed. This discourages weeds, keeps the soil cool and conserves moisture.
  • The clearly defined permanent beds make crop rotation easier.
  • When the beds are raised above the surface of the ground, the soil warms up faster in spring than traditional flat row gardens. This can be a significant advantage in heavy soils and in cool climates. They also drain faster, which can be important in wet spring weather.
  • Raised beds work well in difficult (shallow, alkaline, very poor) soil. They are the best way to garden in very polluted soil (such as that contaminated by heavy metals), as you can simply import soil and create beds above the existing soil ( put a layer of cardboard over the existing soil.)
  • Using raised beds minimizes the area to be cultivated, fertilized, weeded, watered and tended.
  • Established growing beds can easily be cultivated by hand, whereas row gardens can require mechanical help.

Disadvantages

  • Growing beds require more work, water and nutrients if they are to reach their full productive potential. They are a fairly high input and labor intensive way to garden, that makes the most sense if you have want to grow as much as possible, but only have a limited amount of room (such as are found in many modern housing developments).
  • In some soils a raised bed may be hard to re-wet when it gets dry, the water simply runs off rather than soaking in. In such cases you can give the bed a concave top (see Bed Shapes below).
  • Raised beds can dry out quickly in hot, dry climates. In such situations it makes more sense to make the growing beds flat (you can still get the other benefits.)
  • Tall and big crops (tomatoes, peppers, squash) are not so well suited to wide rows as they prefer to have plenty of space around them. Often you will only plant two rows down the length of the bed.
  • In humid areas plants that are grown very closely packed together may suffer from disease problems.

Creating growing beds

Bed size

The width of a bed is usually decided by how far you can comfortably reach to the center. This usually works out to a bed somewhere between 3 and 5 feet wide. Wider beds give you more growing area, while narrower ones are more convenient to work with. They are easier to dig from each side and step over, so there is less chance you will stand on them (you can also straddle them with a wide garden cart.) However they require more paths, which means less growing area, which may be an issue in very small gardens.

It is convenient to standardize the width of a bed, as it facilitates planning and record keeping and you can use standard size cold frames and row covers. French market gardeners made their beds to conform to their standard size cold frames.

Bed length is less critical than the width and is usually dictated by the size and shape of the site. Don’t make the beds too long though, or it becomes a nuisance to walk all the way around them (this is particularly important if the paths are narrow). One way to decide on a length for the bed, is to make the length multiplied by the width into a nice round number (e.g. 4 ft x 25 ft = 100 sq ft, or 5 ft x 40 ft = 200 sq ft). This simplifies your garden mathematics (yield per square foot, how much amendments to add, etc).

To maximize the growing area you may want to keep the paths fairly narrow (in small gardens they can be as narrow as 12 – 14˝). If you make the paths narrow don’t make the beds too long, as you can’t easily get a wheelbarrow down very narrow paths. You don’t want to have to carry spadefuls of compost half way down a 100 foot bed. Generally it’s a good idea to bisect your garden with a nice wide path, so the furthest distance you would have to carry that spade would be 25 feet.

If you have lots of space you can make your paths wider (18 – 24˝), to facilitate getting a wheelbarrow between them. The disadvantage of wide paths is that you have more unproductive area to take care of.

Bed shape

The majority of people fill their gardens with rows of straight beds without thinking about any other option. Straight beds make sense if you just want to grow as much food as possible in a small area. They are easier to enclose with wood, easier to set up for watering and easier to protect with gopher wire and bird netting. Their uniform length and width also makes it easier to calculate the square footage of your crops.

If you are of a more artistic inclination you might consider the possibility of using more interesting shaped beds. These greatly affect the appearance of the garden and are worth a little thought. Curved beds can create an interesting pattern and give the garden a more informal and attractive appearance. Circular keyhole beds are favored by permaculture gardeners. They say there is more growing area and less path and they are easily irrigated with a single sprinkler. I’m not totally convinced by these arguments, but I do like the way they look.

Bed preparation

Any kind of bed preparation takes some effort and is one of the most physically demanding aspects of gardening. I have heard people say that they aren’t strong enough to prepare their own beds, but it is really a matter of conditioning and isn’t that hard. If you are not very fit or strong you just have to do it incrementally. Prepare a couple of feet of bed every day, and you will soon have all of the garden you need. You will also get stronger by doing it and will be able to do more next time – in a few weeks you will be able to happily double dig all day! This is another way your garden can help to take care of your body. You do have to be careful and conscious however, or you can hurt yourself. Fortunately much of the heavy work of establishment need only be done once. In later years the work becomes easier because the soil is in better shape and doesn’t require quite so much preparation.

When to prepare beds: The right time to prepare the beds depends on the soil texture and moisture content. Clay and silt soils are commonly dug in autumn, as the soil tends to be drier at this time (such soils drain slowly in spring and are easily damaged if worked when wet). They were traditionally left rough over the winter to allow the frost to break them down to a fine tilth, but using a cover crop is a much better idea. Clay and silt soils can be prepared in spring if they are dry enough. Light sandy soils can be worked while quite wet, even at field capacity, so may be dug in spring or fall. I prefer to do most of the preparation in fall (including double digging) and then plant a cover crop to protect the soil over the winter.

Moisture: Before you do any kind of cultivation the moisture content of the soil must be right. If the soil is too wet, or too dry, not only will it be much more difficult to work, but also you may damage its structure. Start monitoring the moisture level a few days before you want to start digging.

Too wet: One of the quickest ways to damage the soil is to cultivate it while it’s too wet. This mashes the softened soil particles together, closing pore spaces and destroying the crumb structure. It is also physically harder to dig wet soils, as it sticks to your spade and boots rather than sliding off.

To test if the soil is suitable for digging, take a handful of soil and lightly squeeze it into a ball. Drop this from waist height, if it doesn’t break up it’s too wet to work with (obviously sandy soils don’t stay together as readily as clay ones). If you poke your finger into the ball it should fall apart. If you walked upon the wet soil (which of course you wouldn’t dream of) your footprints would initially be shiny as water is squeezed from the soil.

If the soil is too wet you must postpone working until it has dried out. As a desperate measure I have hastened drying in wet weather by covering beds with plastic sheeting or cloches to stop them absorbing any more water (these are also useful to help the soil warm up). Sloping sites drain a lot faster than flat areas, which is one reason they are considered to be superior. Cover crops can help the soil to dry out faster in spring.

Too dry: Dry soil often becomes a problem in hot weather. Clay soils are the most problematic, as they can bake very hard when dry (they may be almost impossible to penetrate) and tend to crumble to powder when cultivated. When the powdered soil gets wet again it sets solid almost like concrete and becomes impossible to dig. The soil is too dry if it won’t hold in a ball when squeezed in your hand.

The remedy for dry soil is simple, just water with an overhead sprinkler overnight. It’s important to apply enough water initially, as a dry soil can absorb a lot of water (sometimes several inches of water!). Don’t apply too much of course, you don’t want to have to wait for it to drain before you can start work.

Water has a miraculous effect on dry clay soils, when it is dry you need a pick to make a mark, but once it is moist you can push a fork into it.

Clearing existing vegetation

Before you can prepare new beds you have to deal with the existing vegetation. The easiest way to do this is to cover the ground with black plastic for several weeks, which kills most plants by heating and depriving them of light. This is a good way to deal with tough sod with a dense network of roots.

The commonest way to deal with the vegetation is to incorporate it as you dig the beds. You can also remove the vegetation from the soil surface and compost it separately. See Soil improving Crops for more on these.

Loosely rooted old crops, weeds and soil improving crops can often be pulled by hand, but well established crops may require thorough skimming. If there is a lot of vegetation, you could scythe off the tops for composting and incorporate the roots into the soil.

Removing tough grass sod is particularly hard work. You may have to cut through a section on all sides, slide the spade underneath to cut the roots and then lever it from the ground. Don’t bury (or chop up) perennial weeds or grass clumps, as they may start to grow. It is amazing what will survive and grow if you give it a chance, I’ve seen alder twigs root themselves. The end result should be a totally clean area of soil with no plant material on it at all). Grass sod can be composted in a special pile to make valuable turf loam (see Compost and composting).

An easy way to kill existing vegetation is to cover the soil with black plastic for a month or so. The extreme version of this is soil solarization, which can be used to kill a variety of soil pests. See Soil solarization for more on this.

Marking out

The next step is to mark the layout of the beds.  

Linear beds: Most gardeners use rectangular beds because they are easier to water, set up drip irrigation and lay gopher wire in. Once you have decided on their size and location, set out string lines and pegs to define the edges. Keep these almost at ground level initially, so they are out of the way while digging. These will help you to make all of the beds perfectly straight and uniform in size and shape. This makes them look better, though it won’t make them any more effective. If you don’t care about the beds being straight and uniform, then you can forget about this, but the edges of your beds may wander all over the place.

Non linear beds: If you want a more interesting looking garden you might go for curved beds. They are slightly less practical, but really can add visual appeal. Perfect circles and arcs tend to look a lot better than misshapen ones, so make a compass from a length of string and two stakes, so you can get nice neat arcs and circles. Mark the lines on the soil with ground limestone or wood ashes (fill a coffee can with ground limestone and punch a ¼˝ hole into the plastic lid). You can lay out irregular curves with a hose pipe, just lay it down to define the required curves and then mark out the shape with ground limestone.

There are several ways to make a bed, depending upon the condition of the soil and how much effort you want to expend. I will start with the most labor intensive procedure for preparing a “standard” intensive raised bed and will then describe some of the easier (or harder) methods.

Digging the beds

The initial establishment of a raised bed garden is quite a lot of work, especially if you intend to double dig the beds. Fortunately there are ways to reduce the work (and the stress on your body) to manageable proportions.

•      Don’t exert yourself any more than you would in your everyday life, or try to do too much at once. This is especially important in spring when your muscles have weakened from winter inactivity (this is the commonest time of year for injury). If you have any medical problems I suggest you avoid double digging altogether, as it is strenuous.

•      Double digging is hard work, but it can be enjoyable if you work slowly and carefully. Dig only a small section at a time (perhaps 30 minutes a day), resting as necessary. I am fairly fit and strong and I find the repetitive hard labor of double digging quite therapeutic in small doses. More like a combined exercise and meditation than an unpleasant chore.

•      Break yourself in slowly and you will soon be able to double dig from dawn to dusk (or even dusk to dawn if you are particularly gung ho).

•      Don’t strain yourself by picking up more soil on your spade than you can comfortably lift. Two small loads are a lot less stressful than one big one. You should also understand how your body works, even the strongest people can injure themselves through poor body mechanics. Bend your knees when lifting, rather than bending from the waist (I admit this is one I have never quite got the hang of). Use your strongest hand to hold the bottom of the spade (where the weight is) and use your weakest arm to counterbalance and maneuver it around.

•      Dig efficiently. Jump on to the spade and use the weight of your body to push it into the ground, rather than trying to use your arms and back. Use your heel or the middle of your foot to press down on the spade. Learn to lever and slide the spades full of soil into position rather than lifting them (they break up less and it greatly reduces back strain). Push your spade (or fork in heavy soil) into the ground vertically for deepest penetration.

•      You don’t have to dig down the full 24˝ the first time. If it’s a lot easier to only go down 15 – 20˝ that’s fine. You can go deeper next time, when the soil is looser and the digging is easier.

•      If you have enough time you could plant deep rooted cover crops for a season to loosen the soil before digging (see below). This is a good argument for establishing the garden incrementally, over several years.

If you are not very strong and fit, you may want to spread this digging over several years, doing 1 or 2 beds each year.

Tilthing

The prepared bed may need to be tilthed to break up any remaining soil clods and leave a fine loose tilth. The larger lumps of soil are broken up with glancing sideways blows with the fork (sideways to minimize the compaction that might result from downward blows). This should be done immediately after digging, otherwise the soil may dry out leaving hard clumps that are almost impossible to break apart. If you did your digging and forking well then only a minimum of tilthing should be necessary.

Shaping the bed

The best tool for shaping beds is the back side of a rake (the front side doesn’t work very well because the tines have a tendency to dig in and move too much soil). Begin shaping by removing any leftover debris, hard clumps of soil, rocks and weeds (rake them into the path and remove – clods of soil can be walked upon to break them up). To get the required shape pull soil from high spots to low spots, then rake diagonally both ways, as well as straight across. It’s easier to work from the opposite side of the bed, pulling soil up towards you, rather than pushing. I raise the string about 9˝ off the ground while shaping, so it doesn’t get tangled in the rake.

The intended crop dictates how thorough your soil preparation must be. Carrots needs more careful preparation than potatoes or tomatoes. For a seed bed the surface particles should be fairly small, roughly the same size as the seed which will go into them (see Direct Sowing for more on preparing seed beds) The bed may be a lot rougher if you are growing transplants.

Beds shouldn’t be too tall (10˝ at most), I’ve seen raised beds that were 18˝ above the paths and looked more like fortifications than a garden. Beds in clay soils can be higher than sandy ones, because they hold water better and benefit from increased aeration. If beds get too high, you should either raise the path, or remove some soil (this can be added to the poorest beds, or used for propagation or composting).

Bed profile

There isn’t one correct profile for the top of the bed, it depends on the soil, climate and the crop to go in it and there are a number of variations.

Gently rounded beds are preferred for numerous small plants such as lettuce or spinach. These go right to the edge of the bed (especially if they are to be broadcast) and this shape gives you the greatest growing surface. If your soil doesn’t absorb water easily, then sloped surfaces may not be a good idea – you apply water and most of it simply runs off.

Beds with flat tops and steeply sloping sides (no more than 45° or they will erode) are used for root crops such as carrot (they ensure a more even depth of soil). They may also be used when only a few plants will go in the bed (e.g. tomatoes, cucumbers), or where plants will be in rows (such as peas or beans). If the soil isn’t very good you should make sure the top of the bed is totally flat, otherwise water may run off instead of soaking in. You might also create a lip at the edges to help it hold water. In some cases the center of the bed may even be slightly sunken to facilitate the penetration of water.

In northern areas beds are sometimes tilted slightly (5 to 10°) to the south, to help them absorb the suns heat, so they warm up faster. To increase this slope, you could use a 2 x 12” board as the northern side of the bed and slope the southern side down to ground level. These beds might also be surrounded by a windbreak (or even a berm of soil) to conserve warmth.

Beds don’t have to be raised at all. In hot dry climates they can be flat, or only raised a few inches, so they don’t dry out so quickly.

In very dry areas the beds may actually be slightly sunken to minimize the use of water. Such beds may also be useful in humid areas for growing semi-aquatic plants such as watercress. To prepare such beds you basically dig a trench the size of the bed, fork the bottom and re-fill it with soil, organic matter and other necessary amendments. Remove the subsoil only; keep the topsoil to one side for re-filling the bed.

Corner stakes

When you remove your string and temporary stakes it’s a good idea to replace them with attractive, permanent, rot resistant stakes, such as 2 x 2’s. These should stick up about a foot or so above ground and permanently define the corners of the beds. They prevent encroachment at the corners and keep hoses from  dragging across the bed and damaging the plants. These can also add a decorative touch if nicely made.

One disadvantage of permanent corner stakes is that if you don’t watch where you are going they are easy to trip over. You might want to round the tops to minimize scraping your shins on them.

Paths

When the beds are finished you should clean up the paths and rake off any debris. Make sure their width is even along the entire length and that each path is of equal width (they should be if you used string to mark the ends). Attractive paths do a lot to make the garden look good.

In dry areas it is best to leave the paths bare, they will bake hard to create a good walking surface that doesn’t provide hiding places for pests. In wet areas bare soil can get muddy, so you may want a covering of sawdust or wood chips. This will rot down in a couple of years and can then be incorporated into the soil (this is actually a good way to add highly carbonaceous material to your soil).

If space is very precious you could even have stepping stone paths and put low growing crops in the spaces in between them. You wouldn’t be able to use a wheelbarrow though.

Watering

Once the bed is prepared it must be watered like a seedbed to keep it moist, even if it isn’t going to be planted immediately (ideally you should plant into the bed as soon as it is prepared). This is also the time to install drip irrigation.

Finished

Don’t walk on the finished beds again. If you absolutely must stand on them for some reason, lay down a board and stand on that.

Ways of preparing beds

Double digging

This is the best known, most thorough and effective way to prepare beds and appeals to the methodical kind of person, someone who likes order and science (and is also fairly physically active). It loosens the soil down to a depth of 24˝ or more, which has a number of beneficial effects. I have a separate devoted to this topic. Double Digging.

Single digging

This is the next step down from double digging, but still allows you to thoroughly incorporate fertilizers and amendments. The process is simply the first part of double digging. Scatter the appropriate amendments on to the bed, dig the first spit, then throw a layer of organic matter into the trench in the usual way and throw the soil from the next trench on top (I often give it a token forking).

Forked beds

This quick and easy way to prepare beds can work quite well if the soil is in good condition (such as in an established garden). It doesn’t work so well on shallow, poor, compacted or weed infested soils though, as they usually need more intensive treatment.

Begin by scattering the appropriate amendments on to the bed, and then thoroughly fork them in to the soil to a depth of 8 – 10˝. The flat tined spading fork is the best tool for this, as it’s more effective at opening up the soil. Throw any topsoil on the paths onto the beds and shape it to the desired shape with a rake.

Tilled beds

Small scale commercial market gardeners (and large-scale home gardeners) often make raised beds with tractors or rototillers. This is the easiest way to create a large raised bed garden, as they require a lot less labor. Of course the resulting beds aren’t as good as double dug beds, though you wouldn’t expect them to be.

There are several drawbacks to the use of mechanical tillers. They are noisy, smelly, expensive, hard to handle and kill earthworms and other soil organisms. Worst of all they pulverize and compact the soil, which has a horrible effect on its structure. They may also cause a plow pan on heavy soils where the tines smear and compact the soil at their maximum depth. If the soil has a lot of pernicious weeds you can’t use a tiller, as you will simply propagate the weeds when you chop them up. On the plus side they can also save a lot of labor and if you are growing commercially they may mean the difference between profit and loss.

To create a bed with a tiller, begin by marking out the entire area to be covered in beds, and spread out all of the amendments on the surface. Then till to loosen the soil in several passes, going deeper each time, until you get to the maximum depth possible. If it’s a large area you may save a lot of time and effort by hiring a tractor to do it for you.

Once the area is thoroughly tilled, set out stakes to mark the outline of the beds (always keep to the paths) and string lines between the stakes. Then transfer surplus soil from the paths to the beds (there is actually a tiller attachment which does this for you). You then shape the beds and plant.

Triple digging (Trenching)

Triple digging is sometimes used in very poor clay soils. Suitable for the serious penitent only, this is “extreme gardening”, a form of self-flagellation for those that don’t consider double digging to be enough work. Basically it’s similar to double digging, but involves moving a lot more heavy soil around, as you dig and move 2 spits deep and then fork the third spit. You can incorporate organic matter at the bottom of both spits.

Enclosed Beds

Garden beds enclosed with wooden sides are everywhere these days and in urban areas they may well be the most popular way to grow vegetables. These beds look neat, make mulching paths easier and because they are somewhat raised they reduce stooping (good for elderly or infirm gardeners).

One reason they are so popular, is that they provide an instant garden and so simplify the task of growing vegetables. There is no need to learn about your soil, if you can simply buy an imported soil mix. All you have to do is build the beds (or pay someone to build them), fill it with mix (or pay someone to fill them) and you have an instant bed, ready to plant (or you can pay someone to plant). In no time at all you will be eating vegetables you have grown yourself (or be paying someone else to eat them for you). The only problem with paying someone else to create your garden (not to mention buying the soil), is that it thoroughly messes up the economics of growing vegetables.

Though generally I tend to be averse to the world of instant gratification and associated consumerism, in this case I am a little more understanding. If this is what it takes to get people to grow vegetables, I have only a very small problem with it (and who am I to comment anyway?)  Okay since you asked, my problem is that the owners of such beds haven’t put much emotional investment in them and frequently they tend to not take them as seriously (of course that’s not my problem). This is why you frequently see abandoned, half empty enclosed beds.

These kind of beds are great for people not physically strong enough to garden in any other way. They are also useful if your garden has very poor soil (such as a highly alkaline or rocky one), as you can simply import soil to fill the frames. They are the best way for creating gopher free beds, by simply stapling gopher wire to the bottom of the frame (make a good tight fit). Wooden frames also make it easy to create a modular system for attaching drip irrigation, trellis or cloche hoops.

I have used wooden beds for years to combat gophers, but have never grown to love them. My biggest objection is that they are time consuming and labor intensive to make. They also require the use of quantities of lumber, which isn’t very ecologically sound as it usually doesn’t last very long, unless it is expensive rot resistant wood, or treated with toxic chemicals (I always used salvaged redwood). The edges of the bed can provide hiding places for pests (soil sometimes shrinks away from the boards slightly, leaving a crack that is a perfect hiding place). They also tend to dry out fairly quickly. I also found that if they weren’t built and maintained carefully gophers would sometimes get into them anyway.

Another significant problem, is that when you raise up the beds vertically, you expose the sides to sunlight and the soil can heat up much more than it would in the ground. This can be a big problem, because when the soil gets above 80°F, organic matter breaks down rapidly. I often see neglected wooden beds that are half empty, a result of most of the organic matter they once contained being destroyed.

The material for the sides of the bed may be railroad ties (beware of toxic chemicals), concrete blocks, bricks, stone or wooden 2 x 10’s or 2 x 12’s. You can fill them with garden soil, mixed with compost or aged manure and other amendments

Square foot gardening

This is a variation on raised bed/wide row gardens that was popularized by Mel Bartholomew. It is particularly well suited to creating gardens in very small areas, such as patios or decks. You build wooden beds and fill them with an imported mix, thus avoiding a lot of work, time and tools. It is called square foot gardening because you plant each crop by the square foot, putting in a certain number of seeds or plants in each square foot of soil. This is gardening reduced to a minimum and works well for many people. It doesn’t produce an enormous amount of food however and is best used to grow expensive gourmet foods like heirloom tomatoes.

A quick and easy way to prepare a growing bed

If the soil is already fairly fertile, you don’t necessarily have to  spend a lot of time on bed preparation, you can make lazy beds. This is an old peasant technique that minimizes the work required to establish new beds on grassland.

The simplest way to prepare lazy beds is to mark out the area of the bed with string and then cover it with a barrow load of manure for every 50 sq ft. You then cut the turf from the paths and fold it over so it falls upside down on the bed. You then finish by removing any topsoil from the paths and pile it on the bed.

A more elaborate method is to skim off the turf, lay down a layer of woody brush and then replace the turf upside down (include the turf from the paths). You then add layers of manure, compost or other organic matter and finally a layer of soil skimmed from the paths. In cool weather the decay of the bed can be hastened by covering it with black plastic.

Lazy beds should initially be planted with a vigorous crop like potatoes, that doesn’t mind a rough seedbed. Their cultivation involves turning the soil three times (planting, hilling and digging), which thoroughly loosens the soil and transforms it into a real bed. In future years this can be used for other crops.

If your soil isn’t very fertile, you may want to think about growing green manure crops in most beds initially, to improve the soil. You might also think about adding rotting wood to the soil.

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