Raised Garden Beds – Part 1

2018 November 7

Not much green left in the garden -- a bit of chard, some Chinese cabbage, and a lot of kale. Other than raking and mulching, I don’t have a lot of garden tasks this fall.  So, my mind turned to the future as I wandered the yard.  I focused on a wood picnic table that is falling apart and it occurred to me that it might be repurposed into a Raised Garden Bed (RGB).

I first saw a RGB in the 1970s in Colorado Springs. An older lady who’d been an avid gardener all of her adult life could no longer knell down to the ground but still wanted to do some hands-on gardening.  She did have enough money to hire someone to take over the bulk of the yard duties.  So, she had someone make a RBF in the side yard outside her kitchen. I don’t recall the exact dimensions, but it was about 4 ft wide, 8 ft long, and 2 ft high.

Built of hefty lumber, it was easy to sit on the sides and reach all parts of the bed. When she later needed a wheel chair, she could still access her garden.  I don’t remember what she grew in her bed, but it was always beautiful and tidy and made her happy!

There are a number of reasons to use a RGB. In addition to ease of access you can control the soil, extend the growing season, and simplify weed and pest control.

The soil in our yard originally ranged from clay to sand.  It’s taken many years to improve it.  If you install a new RGB, you can add good soil all at once. Several web sites say using light soil allows you to plant seeds closer together since the roots can expand easier and deeper. And, air and water more effectively reach plants than in poor soil.

The soil in a RGB will warm sooner in the spring than ground soil so you can plant earlier.  Also, planting above ground level helps tender plants such as nasturtiums avoid freezing due to late frosts.  I’ve found this to be true in the various large pots I have around the yard.

So what are the cons of RGBs?  The cost of creation could be a problem.  If you can find suitable building materials such as my dilapidated picnic table, the cost of the container is mostly your time.  I was surprised at the range of prices and designs I found on the web. You could create custom beds out of concrete and then decorate the exterior with stone.  Good examples of this are the new ones along Main at the SLV Regional Medical Center. 

At the other end of the price spectrum for purchased containers are galvanized livestock tanks. These are readily available in Alamosa and come in a variety of sizes. Folks consider the material low risk to humans if your bed will be used to grow vegetables.  Livestock have been safely drinking water out of them for a long time!  It is a good idea to make drainage holes in the bottom so you don’t drown you plants.  Another consideration is that thin walled containers may allow the soil to dry out fairly rapidly so you might need to water more than if using thick sided containers.

A less permanent option is to use hay bales.  They will decay over time, but are inexpensive and readily available in the San Luis Valley. It would be a good idea to find out how the hay was grown if you are trying to avoid herbicide, disease, and/or weed contamination.

Railroad ties sound like a great idea as they are thick and heavy.  However, many are treated with creosote. According to the EPA website, “...Creosote is not approved to treat wood for residential use, including landscaping timbers or garden borders… Creosote is a possible human carcinogen.”

Another material to avoid, according to Joe Lamp’l of the JoeGardener.com website, is tires. He says, if you must “do it only for a season or two at most. Tires are a petroleum-based product. Their rubber degrades in the heat and moisture, and the chemicals incorporate into your soil.”

There are a wide variety of kits available.  Just make sure the materials won’t contaminate the soil if you plan to raise food.  Also, be aware that moisture and sun exposure can shorten the life of many materials.  Some people add plastic liners to retain soil moisture. It should only be used on the sides to avoid drainage problems and should be food-grade polyethylene if you’re growing food.

A future column will discuss filling your RGB with soil, planting, and maintaining.

“Of all the seasons, autumn offers the most to man and requires the least of him.” Hal Borland