Raised Beds – Pros & Cons

Robert Pavlis

Raised beds are becoming more popular, but do they make sense for the garden? What benefits do they provide? Will they grow more food than convention low beds? Does a raised bed need to have side walls? What is the best building material and soil for raised beds? In this and the following posts I will try to answer all of these questions so that you can make an informed decision about adding raised beds to your garden.

Raised beds with hoops
Raised beds with hoops

What is a Raised Bed?

The term raised bed is a bit confusing. If you add a few inches of soil to a garden bed that is at ground level, it is a raised bed. When most people talk about raised beds for vegetable growing, they mean a bed that has been raised with walls surrounding the soil, sometimes called a garden box or framed bed.

I’ll use the term raised bed to mean a bed that has walls and compare it with a traditional bed that does not. A traditional bed may or may not be raised above grade, but it is usually not raised more than six inches.

Benefits of Raised Beds

The pro side make many claims for using raised beds. The problem with many of the claims is that they are not comparing apples to apples. When you compare raised beds, using intensive cultivation to traditional farming practices you do find many benefits, but that comparison makes little sense. If you want to understand the real value of raised beds you need to compare them to intensive gardening done on level ground, or even raise ground without side walls.

Compost Science for Gardeners by Robert Pavlis

I will look at many of these myths in a future article on GardenMyths.com, but for now here is a summary of some claims for raised beds that are not true.

  • need fewer seeds
  • has fewer weeds
  • more productive
  • longer growing season
  • less compaction

YouTube video

Raised Beds – the Pro Side

There are some legitimate reasons for using raised beds.

  • The garden looks neater. The walls keep soil in place, and pathways can be kept cleaner.
  • They require less bending to work on the plants, but a 12 inch wall does not help much for us tall folk.
  • They can be used in areas that have very poor soil, contaminated soil or no soil at all. Containers are small raised beds.
  • They warm up quicker in spring, allowing earlier planting.
  • They can be great for people with a disability.
  • Different beds can hold different types of soil allowing you to match soil to crops.
  • Drainage can be better in areas with very poor drainage, but raised beds can also cause drainage problems.
  • Bottoms can be screened to keep gophers and voles out.
  • Helps keep kids and pets from stepping onto plants.
Raised beds for handicapped
Raised beds for handicapped

Some people claim  they deter slugs and animals like rabbits. Others say they have no effect on these pests.

Raised beds may help concentrate resources like compost and fertilizer to the growing areas, but if you are careful you can also do this in a non-raised bed.

Notice that none of these reasons have anything to do with higher productivity, better flavor or improved nutrition. If you grow the same food, in the same kind of soil, raising the soil level and adding walls will produce exactly the same food as growing in the ground.

If you use better soil in a raised bed then it might produce more food, but you can also use better soil on the ground.

Techniques like square foot gardening make all kinds of claims for improved productivity, but the reason for increased productivity is due to intensive cropping – not the raised bed. You can do all of the intensive cropping on level ground.

Raised Beds – the Con Side

There are some very good reasons for not using raised beds.

  • You have to buy soil, unless you have high spots in your yard that you want lower.
  • They cost money to build.
  • Soil dries out much faster in summer.
  • Requires more watering.
  • Less sustainable since you need to buy and transport walls and soil.
  • There is some concern about chemicals leaching from the material used to build the walls.
  • Soil gets warmer, which is not good for roots, except in early spring.
  • Perennials need to be hardier since a raised bed gets colder in winter.
  • The rows between beds need to be wider if you plan to use a wheelbarrow with taller walls.
  • Drip irrigation is more difficult to install.
  • Soil cools down quicker in fall.

Productivity is probably better without a raised bed. The roots of a tomato plant in the ground grow several feet in all directions, but in a raised bed its root system is confined. Raised beds dry out quicker in summer, and water becomes a limiting factor for yield. Given good soil, and the same amount of fertilizer and water, it is hard to see how plants crammed into a raised bed would produce as much food as in the ground.

Are Raised Beds Better?

Unless one of the pro arguments is very compelling for you, I recommend gardening on the flat ground. This is especially true if you are a first time gardener or someone that might move in a few years. Give it a try before spending the extra time and money building walls.

Read all about intensive cropping, including such topics as wide beds and succession planting. If drainage is a problem, you can move the soil from the paths onto the growing beds to raise them a bit. Adding organic matter will raise them a bit more. With beds that are eight inches taller (no walls) you will have a very productive garden, and the obvious paths will keep you from walking in the growing areas (unlike the lady in this picture).

Vegetables growing in wide beds
Vegetables growing in wide beds – try not to walk on the beds.

Recommended Reading

I don’t normally recommend books, but these are very good for learning more about intensive vegetable gardening.

References;

  1. Photo source 1 and 2: under license
  2. Photo source for Vegetables in wide beds; Kate Holt/AusAID

 

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

19 thoughts on “Raised Beds – Pros & Cons”

  1. I have a problem with my columnar cedars, nearby, sneaking over for new soil, more water, so every spring I must dig up the ground or dig out beds to eliminate their fine roots.

    Reply
  2. I don’t see the books you recommended. Maybe you forgot to type them?

    “I don’t normally recommend books, but these are very good for learning more about intensive vegetable gardening.” But there are no books listed after this. Can you tell us which books you meant?

    Reply
  3. Thanks for the great article on Hugelculture. I was wondering if this was worth the bother to more easily fill a raised bed. Now I know. I’ve been converting all my beds to raised (wood box) beds. So much easier to maintain, weed, plant, and harvest. Cover up the bed for the winter with shredded leaves, plant seedlings in the spring as is, maintain the mulch occasionally with grass clippings, and hardly a weed to pull. The worms are so abundant it also attracts birds and a pesky raccoon. The wire bottoms solve for the moles and voles (but not the raccoon or groundhog).

    Reply
  4. Please provide the link you mentioned about soil for raised garden beds. I am also interested in any updates to using hugelkultur principles when filling raised beds. I saved the wood from small trees that were taken down for the purpose of planning them at the bottom of tall corrugated aluminum raised beds (popular in Australia, but I’m in California, zone 10).
    Many people also modify raised beds into sucking raised beds, but it seems more expensive and time consuming. Would be a good experiment.

    Thank you. I discovered your website today

    Reply
  5. I have converted most of my city garden to raised beds, zone 3b in Saskatchewan. I used cindercrete blocks for the walls (2 high). I do have fewer weeds, even after 4 seasons. The ones that do spring up are very easy to remove.
    I find that my carrots & beets do much better in the raised beds than in the ground. Tomatoes & beans produce about the same either way, although I plant fewer beans in the raised beds. I don’t put potatoes or zucchini in the raised beds.
    Planting, weeding & harvesting are all easier in the raised beds. The soil doesn’t really get compacted. I can loosen it with a hand trowel in the spring. It is also easier to cover plants early & late in the growing season. I may have to water more frequently in hot weather, but I use soaker hoses in the beds.
    If I was starting another garden in the city I would definitely make raised beds again.

    Reply
  6. For me raised beds are productive at 59 degrees latitude on the edge of the rain forest. I fill the lower half to three quarters with logs and twigs, (think hugelculture) and then top with soil. Warms up and dries out early in the spring so I can get a jump start on gardening in this cool, wet climate.

    Reply
  7. My question is about the soil used in raised beds, and I have to use raised beds as I live on Hawaii island that is basically pure lava and absolutely no topsoil. Melʻs mix (1/3 vermiculite, 1/3 peat moss, 1/3 compost) for raised beds is taken as gospel, but does it really matter that much?

    In Hawaii with the expensive costs of soil it would be more than $80-100 for just one 4 X 8 ft raised bed if you followed the formula recommended by the many online disciples of Mel. I am going to try using black cinder instead of vermiculite, and get soil however I can, but has there ever been any scientific tests to verify Melʻs formula? This formula seems very dogmatic and unproven, but it must work for a lot of people?

    Reply
    • An upcoming post will be on soil for raised beds. The best soil is natural soil. Mel’s mix is popular but not supported by science. Vermiculite has no place in the garden and 1/3 compost is too rich. with this mix 2/3 will slowly decompose and need to be replaced every year.

      Reply
      • Thank you Robert for all your great posts. I recently stumbled across your site and have been reading on a variety of topics. You’ve already saved my over $100 as I’ll not be buying that compost tumbler, and your cut and drop method of composting, wonderful.
        My question today is about keeping horsetail out of new raised beds. Horsetail has got into my flower gardens, lawn, and old vegetable garden. Apparently the only way to discourage it is to cut it or smother it; heavy cardboard is recommended.
        I want to start a new vegetable garden in raised beds. Was planning to put heavy cardboard – large boxes that held folding tables – on my lawn and put the raised beds on top of that and fill with topsoil. What about putting a layer of landscape fabric under the cardboard? My thinking is that the cardboard will eventually deteriorate, but the fabric will be there as a barrier, just in case. But that would mean earthworms could not get into the raised beds.
        I would appreciate your thoughts on this. Will the heavy cardboard alone be enough or would landscape fabric be worthwhile insurance against horsetail getting into the raised beds? Or would it be better to not use landscape fabric so the worms can get in? Thanks.

        Reply
  8. For me, the mains reasons I put in raised beds where:
    1) not having to get ride of my grass, I could build raised beds with 2x6s and put cardboard on top of the grass, and add some composted manure to the top. This saved the cost/effort grass removal, as it broke down naturally.
    2) Neatness. In my 1/4 acre yard, it matters.

    I certainly didn’t fill up the bed, so the compost costs were minimal at a couple dollars per 50lb bag.

    Reply
    • I do like the look of raised beds.

      Some people are building beds that are 2 or for feet tall. That requires a lot of soil.

      Reply
    • As my health worsens the gardening gets harder each year. Eventually it is going to be a choice between raised beds sufficiently high enough that I can easily reach, or no garden at all.

      Reply
      • If you have access to wood chips they can be a great filler for a raised bed. I get my chips for free. Our raised beds are 36 to 40 inches tall which makes for easier sowing, tilling, weeding and harvesting.

        Reply
  9. Thank you Robert for your podcasts on planting pre-germinated seed. There is plenty of info on pre-germinating but yours was the only one I found on how to plant them after they have a radicle.
    Best Wishes,
    Larry

    Reply

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