Raised Bed Gardening FAQ

By: Julie Day
Raised planting bed made from brick

Brick is a good material for raised planting beds.

Here are some frequently asked questions and answers about how to construct and plant a raised bed garden in your yard.

Q: What can I plant in a raised bed garden?

A: You can grow anything in a raised bed, from vegetables and herbs to flowers, bulbs, shrubs, and trees.

Q: Is raised-bed gardening different from regular gardening?

A: Raised beds are dryer than the surrounding soil, so they’ll need more water during summer. There are many advantages to raised bed gardening; but you’ll still need to care for your plants.

Multiple wood raised beds with wide aisles for easy access

Multiple wood raised beds with wide aisles for easy access.

Q: Should I build my own raised bed, or buy a kit?

A: Whether to use a raised bed kit or build from scratch is a matter of preference. Building your own raised bed allows you to customize the design, size, and shape and may cost less. However, some kits have cool features, like watering systems and critter-proof linings.

Q: Are raised beds easy to build?

A: Constructing a raised bed can be simple or complicated, depending on the materials used. Lower raised beds are easier to build than high ones.

Raised bed made from stackable retaining wall blocks

Stackable retaining wall blocks make a durable raised bed that can be disassembled.

Q: What materials can be used for raised beds?

A: There are lots of materials to choose from for raised beds, including:

  • Wood: While more expensive, rot resistant woods – such as cedar, cypress, and redwood – are a great choice for raised beds. Less durable woods can be used as well, but they will need replacing over time.
  • Composite: Made from a mixture of plastic and wood, composite is durable and considered OK for use in certified organic gardens.
  • Masonry: Brick, block, and stone are great choices for raised beds. You can cement with mortar for permanent beds, or use stackable retaining wall blocks for a raised bed that can be disassembled and moved.
Raised bed made from pressure treated landscape timbers

Pressure treated lumber is often used for raised beds but should be chosen carefully.

These materials are a source of debate:

  • Pressure Treated Lumber: Creosote-treated lumber (such as railroad ties) or pentachlorophenol-treated (penta) lumber are definite no-nos for a raised bed. There’s a debate about whether the preservative in other treated lumber can leach into the soil. So far, studies have not shown significant contamination from treated lumber, but it’s still discouraged in organic gardens. If you do use treated lumber, make sure it’s treated with ACQ (alkaline copper quat) or CA-B (copper azole), rather than the older arsenic-containing CCA (chromated copper arsenate) which was discontinued for most uses in 2004.
  • Plastic: Because of the possibility of chemicals leaching into the soil, you’ll find gardeners on both sides of the argument over using plastic materials for raised beds. If you do use plastic, make sure it’s BPA-free, food-grade plastic.
Wood raised bed with weed barrier on top

Wood raised bed with weed barrier stapled on top.

Q: How big should a raised bed garden be?

A: The standard width for a raised bed garden is 4 feet – which is narrow enough to reach into the bed from both sides without having to step in it. If you can only access a raised bed from one side, make it 3 feet wide.

The length of a raised bed garden can vary, but very long ones can make walking around them inconvenient. When putting in multiple beds side by side, make the aisles between beds at least 3 feet wide, to accommodate wheelbarrows.

For more information about garden size and yields, check out Choosing the Right Size Vegetable Garden.

Q: How high should a raised bed be?

A: The higher, the better! Higher beds mean less digging in the soil underneath and less stooping. As a general rule, herbs and salad greens need 6”- 12” of soil while vegetables require 12”- 18”. You can either build your bed to the proper height, or till down into the existing soil. Raised beds for wheelchairs or sitting gardeners should be 24” or higher.

Q: What kind of dirt should I put in a raised bed garden?

A: The best soil you can get! One of the benefits of raised beds is the ability to control the soil. If you have a compost pile, mix it into the soil in the raised bed. Potting mixes from local landscape supply yards also work well and can be purchased by the truckload or delivered.

Mix rich soil with the existing subsoil in a raised bed garden

Mix rich soil with the existing subsoil in a raised bed garden.

Q: How do I prepare an area for a raised bed?

A: The best raised beds mix the new, rich soil in with the existing soil underneath, to prevent having a sharp delineation between soil textures. To do this, you’ll need to remove the grass, till, and level the ground underneath your raised bed location, then incorporate compost and organic matter into the ground soil before topping off the bed with new soil.

If the bed is higher than 12” you can probably get by putting the new soil on top of the grass, but line the bottom of the bed with biodegradable paper or landscape fabric first to prevent weeds.

Q: Can I adapt raised beds for shade or to keep out pests?

A: Raised beds are very adaptable – the easiest solution is to use flexible PVC pipe or bamboo bent into an arch and tucked into the side of a raised bed to form a frame for shade cloths, frost cloths, or bird netting.

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4 Comments on “Raised Bed Gardening FAQ”

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  • Amber Says:
    April 8th, 2015 at 9:50 pm

    I have an old raised flower bed surrounded by wood. Unfortunately the wood is all rotten now. I’m wanting to replace it with bricks or something but im not sure how to do it. Any thoughts?



  • darleen Says:
    May 16th, 2013 at 4:51 pm

    Two questions. I am planning to build a raised flower bed using retaining wall blocks. It will be up against my vinyl sided garage. Right now there are landscaping stones covering this area. Question 1: Can I just lay landscaping fabric over the landscaping stones and pour soil on top of it. Question 2: What do you suggest I use to protect my vinyl sided garage other than rows of brick.



  • Troy Says:
    April 10th, 2013 at 6:49 pm

    I’m plannig to put a raised bed on a concrete surface.
    I’m either going to use cedar or concrete blocks; I plan to have drain holes on the bottom of the cedar or towards the bottom of the concrete blocks.
    Which would you recommend?

    Thanks



  • Roseline Says:
    July 18th, 2012 at 5:10 pm

    I don’t know about any plans, but I built some elevated beds by tnakig a piece of 5/8 treated plywood and building a stand for it out of 4 4 s. The stand has to be pretty stout, it will be holding a lot of weight. Build the frame first then set it on the legs, It has six legs. I have a full frame around the outside with two cross pieces evenly spaced from end to end. I cut sides and ends out of another piece of plywood 16 tall and then attached them to the floor by running a 2 2 around the edge , set back far enough so that the outside of the sides and ends are even with the edge of the floor. I ran another wall across four feet from each end and stiffened that with 2 4 s. I used screws throughout that are rated for use in treated lumber.I have three of the beds that are three years old and still going great. Don’t forget to drill holes in the floor for drainage.


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