The Dirt on Raised Garden Beds: Mining the Urban Waste Stream for Building Materials

By December 29, 2011Sustainable Landscaping

Many recycled and repurposed materials can be sourced from the urban waste stream and used to create planting containers and raised garden beds. Which materials are safe and non-toxic? Which materials are the most durable? I have unpacked the options with this investigation on the pros and cons of a variety of potential materials.

Labyrinth garden bed

Here is a set of criteria that can be used as a guide. First, lets consider the toxicity of different available building materials on a scale of 1 to 4, with 1 being completely non toxic and 4 being relatively toxic. Which end of the toxicity scale you choose depends on whether you are growing food crops or ornamentals? This is an important determining factor for obvious reasons.

The second criteria is longevity. This I rate from A to C, where A is for materials that are short lived and C for materials that can last over 20 years. I have combined these two criteria in the table below. They will help you determine the most appropriate building materials for your garden project. I have populated this table with different materials that I have used over two decades, with a description of their merits.

Toxicity and longevity table for repurposed and recycled building materials.

1) non-toxic2) semi non-toxic3) relatively toxic4) toxic
A) 1 seasonstraw baleold guitar
B) 10 yearsold tea pot  old saxophone old tuba wine bottles wine barrel drift wood logs salvaged lumber redwoodold shoes,  old bootsold doors  old boat old dresser
C) 20 + yearshorse trough  reclaimed metal old toilets old bathtub urbanite brick stoneRecycled plastic lumber  copper pressure treated lumberArsenic pressure treated wood  vinyl old tires

You may see things on the table that make you wonder, “What? planting container?” Don’t worry I’m just pushing the envelope on possibilities. Our cities’ rubbish bins are teaming with items and materials that can be used to contain plants. So consider this a fishing license for the urban waste stream. One man’s trash is another man’s planter.

For instance, my old food blender recently gave up the ghost. Instead of just tossing it in the trash I filled the blender “container” with soil and planted it with succulents.

Blender planter

Of course I have inserted into the table many of the conventional building materials used for raised garden beds. Here they are with a description of their merits. In another instance someone had a “Jimi Hendrix moment” with their guitar and threw away the smashed instrument. I pulled it out of the trash, put soil in it and planted it with succulents. People are delighted when they see it, especially when they hear the story behind it. As you can see I cast a wide net in the search for building materials for the garden. While I’m on the subject…I’ve been on the lookout for a tuba that maybe was run over by a school bus. I want that tuba for a planter and I am going to call it garden art.

I) + A) Straw bales

Straw bales are inexpensive and if you are resourceful even free.  Tomato starts can be planted right in the bale just by replacing a handful of straw with a pocketful of soil. As the photo shows, straw bales can be configured as raised garden beds, filled with soil and planted. Of course the bales will only last for a season and then become compost. A short-term, cheap, non-toxic and fun way to build a temporary garden bed and soil at the same time.

Straw bale planter

Raised bed made from straw bales

Growing tomatoes in straw bales.

1) + B) Old tea pot, old saxophone, old tuba, wine bottles, wine barrels, driftwood, logs, salvaged lumber, redwood. The teapot, saxophone and tuba used as planters are all examples of playful, whimsical garden art. Metal, ceramic or porcelain items will all be long lasting, non-toxic plant containers, (Hint: dril a hole at the bottom for drainage.) Wine bottles planted upside-down and side-by-side can make an attractive garden border. An up cycled creative re-invention of a common household item. Wine barrels have been used as planting containers ever since vintners started casting them off. They last up to 10 years and are pleasing to look at, brimming with herbs or flowers.

Wine bottles for edge

Wine barrel planter

Driftwood and logs are often available for free, and can make fine raised garden beds that last 10 years or more. These materials can be simply laid in place without much more to do.

Salvaged and redwood lumber: With a little surfing on the internet at FreeCycle or CraigsList, can located. New redwood and other hardwood lumber that has been sustainably harvested can be found if you trust the Forest Stewardship Councils’ “FSC” label. It is nice to think that sustainably harvested lumber is available, I have found small scale local mills to be trustworthy. Redwood can last ten years with soil up against it. With a little carpentry these lumbers make fine garden beds.

Salvaged lumber

Sustainably harvested redwood

1) + C) Horse trough, reclaimed metal, old toilets, old bathtubs, urbanite, brick, stone

For horse trough, reclaimed metal, old toilets and old bathtubs: The size of troughs and bathtubs make them viable as raised garden beds. Reclaimed metal and old toilets require some artistic license but can be turned into long-term plant containers.

Re-purposed horse trough

Salvaged iron metal

Toilet planter

Bathtub bed

1) + C) Urbanite, Brick & Stone

Urbanite is the funny made-up non-brand name for repurposed concrete pieces. A surprisingly available, long-lasting, non-toxic building material sourced from the urban waste stream. Earns high marks for environmental friendliness. Brick is laborsome to manufacture; however when installed correctly it gets high marks for longevity and being non-toxic, especially when used without mortar. It’s fairly easy to repurpose again and again. Often found available used on Craigslist.Stone, (flagstone, granite, field stone, river cobble, pea gravel, etc.) is without question the quintessential non-toxic building material. However, questions do arise regarding its source. It is a mined product that carries a heavy environmental cost but makes up for it in longevity, especially if it is salvaged and re-used. Unparalleled aesthetics in the landscape earn it high marks.

Raised Garden beds using 'urbanite'.

Sonoma field stone

2)+ A) Old guitar

Okay, okay…short term garden art. Mine is about four years old and it’s falling apart. But it sure has a good story behind it.

Blog author Ken Foster and his 'Jimi Hendrix moment'

A crafty guitar

2) + B)  Old boots and Old shoes, These bootswere made for walking…but now they’re retired and growing strawberries. Good thing there is a hole at the bottom for drainage.

Growing strawberries for Nancy Sinatra...These boots where made...


What are these planters doing in the trash?

Comes with drainage.

2)+ C) Recycled plastic lumber, I like that there is plastic . I have seen raised garden beds made from old doors. Old doors, as well as old boats and old dressers they may have paint and/or glues to wonder about. Still, I’ve dreamed about getting an old (small size) fishing boat, filling it with soil and growing food in it.

Open door policy in the garden

4)+ C) Pressure-treated wood, copper pressure-treated wood, vinyl, old tires

Fun but toxic.

Now we’re getting toxic. In the old days as late as the nineteen nineties, pressure treated lumber was impregnated with arsenic. Then children started showing up with cancer from playing on structures made with it. That product was taken off the market and while copper tressure-treated wood is much better, I still don’t like growing food in it. The jury is out on using it for garden beds. Virgin vinyl is an extremely toxic product and I don’t like the idea of growing food in it. Then there’s old tires. Recycling this huge waste problem in the garden? Tires are chock full of heavy metals like lead and cadmium and simply are not appropriate to grow food in.

Now that you have learned a little about the dirt on raised garden beds, build some and put the dirt in them where it belongs. -Ken Foster


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