An Oration on Aeration

“Oh gardener, my gardener, I came to a fork in a garden path and I took the one less compacted”. Thus begins absolutely no poem I have ever read, but nonetheless, an essential gardening truth cleverly tucked away amidst the verbosity.

Oxygen. Roots need to breathe just as much as the rest of us. Roots access the air available in a soil’s macropores. Soil structure is the term soil scientist refer to when discussing the ratio of soil water to air capacity of a particular soil type. The ol’ rototiller, and the shovel before that, were what gardeners have traditionally used to fluff the soil in order to increase soil structure. However, there are several reasons to reduce or even eliminate tilling altogether, although there is plenty of debate, and pros and cons to each side. I even wrote a blog on the subject. A volunteer recently mentioned she was trying to decide whether or not to aerate her flower bed. As a general rule, and as certainly is our practice here at Wellfield, aerating your typical perennial or annual flower bed is unnecessary, and could even be harmful, as the above links show. Even running a hand cultivator through the bed to “freshen” appearances or “get some air to the roots” is not a good idea, as it could damage roots, and it encourages weed germination. One gardener I knew used to run a hand cultivator under trees and shrubs in an attempt to get air to the root zone. All that accomplished was a bunch of torn root fibers. Building soil structure, the whole goal of “aeration,” is better handled with the regular addition of humus, compost and mulch.

Soil compaction is the one exception I make to my low-till operation. Busting through the hard ground, where a large number of visiting feet have trod the lawn, for example, is critical to keeping roots alive and breathing. We utilize a core (plug) aerator for compaction in turf and a broadfork within a bed.

Even more important is preventing compaction in the garden in the first place. There are several preventative measures you can take, including:

  • Avoid stepping into flower beds when soils are saturated,
  • Employ mulch to help disperse the weight of your foot and slow down rain droplet impact, and
  • Develop a path system through the garden (including garden beds) in the highest traffic zones.

The last point is all about design. Incorporating some means of access to the back of the “flower border” is as important as any other feature in a bed design. I have even utilized small wood planks temporarily to walk on if I had to work in a water soaked flower bed in clay soil, pulling up the planks as I go.

It is always a good idea to leave as light a footprint upon the land as possible, figuratively and literally, but if you are a little heavy of foot, make amends with soil amendments, and take the path less traveled just for the fork of it.

Josh Steffen, Horticulture and Facilities Manager


2 comments

  1. This is something that we need to do to one of the big lawns at work, not only because it gets so much traffic, but because it is saturated right below the surface! A rather elaborate drainage systems was installed prior to the installation of the lawn, just because the spot is so swampy. Somehow, it works.


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