Here's the dirt on biodegradable plant pots

By Jim Hole, Edmonton Journal, April 15, 2010

Photo: Biodegradable rice pots are used for the huge crop of geraniums at Hole's Greenhouses in St. Albert. Photo by: Candace Elliott, The Journal, Freelance

There's always a little history repeating in the greenhouse business. When I was a kid, Mom and Dad grew most of our plants in brown, fibre pots. The containers provided an excellent environment for roots, but had one major problem -- the bottoms rapidly rotted.

Eventually, we switched to lightweight, easy-to-handle plastic containers when they became both available and affordable. In the greenhouse industry, plastic became firmly embedded as the standard. But now, we're returning to our roots.

The demand for more eco-friendly products has led to the development of biodegradable containers, meant specifically for the greenhouse industry. And let me tell you, they're a far cry from the rotten-bottomed pots of my childhood.

Not only are these new containers great for growing in, but they also biodegrade after they've served their purpose. And because they decompose, therefore bypassing the landfill, they enrich your garden soil.

On the sustainability scale, they score high.

So just what are these biodegradable pots I'm talking about? Well, most aren't season-long pots; they're growing-in-until-it's-time-to-transplant pots. They're still a bit more expensive than plastic pots, but I think the additional cost is well worth it. Eliminating plastics and giving back to the earth are good reasons to switch. Besides, there really isn't a price tag we can put on our environment.

So with no further ado, here's some info on the biodegradable pots I'm using this year. Note that the fibres in each type of pot are held together by naturally occurring plant resins, which are also biodegradable.

COIR FIBRE POTS

Coir fibres are found between the outer shell of a coconut and the internal shell that protects the seed. They are stringy, flexible and tough enough to be woven. Most coir comes from stockpiles found in Sri Lanka and India. The fibre is also compressed and sold as a substitute for peat moss. Coir pots are probably the least attractive of the biodegradables I've tried, but their permeability is great for increasing vital airflow around roots.

RICE POTS

Rice pots are the most durable and esthetically pleasing of the biodegradables we're using. Smooth, shiny and earth-toned, they're some of the most attractive pots I've ever seen -- biodegradable or otherwise.

The downside, however, is that rice pots are rather brittle, which means they're prone to cracking. At the end of the season, though, that brittleness becomes an advantage -- with one stomp, the pot is reduced to tiny bits, which decompose quickly. Last, but certainly not least, these pots are made from rice hulls rather than the grain itself, so there's no diversion of food to create these containers.

WHEAT POTS

Considering how widely available wheat chaff is, it's not surprising that someone's transformed it into a usable product. Wheat pots are much more pliable than rice ones, which makes them less susceptible to cracking.

However, the green hue of wheat pots also makes them less esthetically pleasing than their competition.

Wheat pots also biodegrade more rapidly than pots made from rice or coir. But that's not a bad thing -- decomposition is what these containers are all about. Just be aware that wheat versions are destined for the compost as soon as you remove the transplants.

While each type of biodegradable pot has its own attributes, all are excellent choices for fostering sustainability. At our greenhouse, we aren't shifting to 100 per cent biodegradable pots just yet. Part of the reason is that a complete product line isn't available. The other reasoning is that plastic still has a place in the greenhouse.

In all likelihood, biodegradable substitutes may eventually eliminate the need for any plastic pots. We are, after all, back to an era where rot is hot.

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