It’s a breeze— how air circulation keeps plants healthy

by SHARON PARKER

Mildew-prone plants like monarda fare better in a breezy spot.

Many years ago, when the Children’s Museum was still in the Midway area, they installed a children’s garden. I asked the gardener how she managed to keep all the plants looking so good without the use of pesticides—which, of course, were simply out of the question in a child-friendly garden.

“Air circulation,” she said.

Sometimes I think that good air circulation as a tool to prevent plant diseases may be one of the best-kept secrets in gardening. Once you learn how to harness it, your garden will be much healthier and you will have less work to keep it that way.
Why? Because plant diseases need a damp environment to grow and spread—the longer water lingers on the leaves, the more the mildew or blackspot spores can multiply. And when people or animals brush against wet plants, they help to spread those spores to other plants.

Whether they’re wet from the dew, rain or a sprinkler, leaves will dry quicker in a breeze than where the air is still.

In addition, plant-eating insects may find it more difficult to settle in for a good meal when the wind keeps them moving along. And when young seedlings sway in the breeze, it makes their stems strong. Studies done on tomato plants started indoors actually showed that brushing your hand over the tops of the plants so that the stems moved back and forth resulted in thicker, stronger stems. A good breeze will do this work for you.

So how do you harness the wind to help keep your garden healthy?

When I participated in a community gardening project in the Bryant neighborhood, we had a master gardener visit the site; he told us to align our rows so they ran north-south rather than east-west to allow the summer breezes, which mostly come from the south-southwest, to circulate through the garden more freely.

Around that same time, I learned not to tuck mildew-prone plants into sheltered corners. At my old house, we had a little niche where the wall of the porch met the back wall of the house—so even though it was open to the south, the breezes didn’t pass through it because there were walls on two sides. It seemed like a sweet spot for a garden, and I planted monarda there; it was plagued with mildew for several summers— not unusual for monarda. But I wondered if there was anything I could do to help rid the plant of the disease. I had tried dousing it with baking soda-and-garlic solutions, I had cut it down to the ground and let it grow anew, but always the mildew returned.

Finally, after learning how air movement can help prevent disease, I dug up the monarda and moved it to an open spot in the back yard, away from the house, where it could enjoy the summer breezes. It was much healthier after that.

It’ s also important to follow the recommended spacing for each plant. You may have read that in small-space intensive gardening, you should disregard the recommendations and plant things closer together; this is said to discourage weeds and get more production out of limited space.

The problem is, the books that advocate that approach were not written by gardeners in humid climates. In Minnesota, close spacing is usually a mistake and can result in the rapid spread of disease and insect problems. The recommended spacing will give your plants sufficient room to breathe and will make the insects work a lot harder when they attempt to jump from one plant to the next.

A much better way to discourage weeds is to mulch generously—lay down newspapers as landscaping “fabric” and cover them with an organic mulch (as I described last month for no-till gardening).

To get more production out of limited space without crowding, use succession planting and vertical gardening. In succession planting, you first plant cool-season crops like peas or lettuces as soon as the ground can be worked (usually in April), and follow that with a short-season heat-loving plant like bush beans, and, if you really want to keep it going, plant another crop of lettuces and peas when the beans are done.

Vertical gardening means training vines like cucumbers and squash on a trellis or fence rather than letting them sprawl on the ground. As you can imagine, this also exposes more of the vine to the air, taking further advantage of the benefits of breezes.

In medieval times, diseases were often thought to be caused by a miasma—stagnant, bad air. The solution was to open the windows and let in a healthy fresh breeze. Now that we understand how germs work, we can appreciate the prescient wisdom of that practice. The same principle holds true in our gardens—let the wind blow through them to keep plants healthy.