What the scent of spring means for your turf

Karl Danneberger

The arrival of spring’s warm, sunny days awakens turfgrasses from their dormant winter state. Brownish turf is replaced by dark green, which announces the rejuvenation of life on a golf course.

As the turf continues its march toward summer, it provides
a few scents along the way.

One of the most striking smells as turfgrasses begin to grow and flourish is the smell of freshly mowed turf. The sweet smell that arises is immediately noticeable. The smell potentially can arise after any mowing, but why is it I notice it most often on Saturdays? Maybe smell is also an aesthetic sense, given I associate Saturdays with being on my lawn or playing a round of golf.

We have the capacity to distinguish more than 10,000 smells, and freshly cut grass ranks among the world’s top smells. A smell originates from molecules that are generally light and that evaporate easily (volatile).

The smell of cut grass comes from a burst of organic compounds from the leaf known as green leaf volatiles, which form within seconds of being cut. The release of these volatiles is a response to the plant being injured. Some of these compounds are produced when turf is damaged by frost.

The release of volatiles is important when the plant is under stress. Some volatiles signal the plant to produce organic compounds like salicylic acid and jasmonic acid. Researchers believe that plants give off a burst of these volatile organic compounds as an antimicrobial defense to protect the wounded leaf from pathogen attack.

Traumatic acid compound is triggered and signals the plant to make more cells to cover up or close up the wound. Some volatiles released into the air act as a call for help. These volatiles include alcohols and esters, which have been reported to attract beneficial predatory insects to help fend off caterpillars or other insect pests. That smell of freshly cut grass is a sign that the plant is signaling its defenses to protect it from microbial and predator attack.

There is a downside to these volatiles. They act as precursors to ozone formation. Australian researchers have found that 20 percent of ozone-causing chemicals can come from vegetation.

Although the volatiles released from turfgrass plants don’t sound enticing, they are similar to the burst of organic compounds released by raw vegetables when you bite into them and chew. So, for staff members and golfers who enjoy chewing on grass blades — feel free — the smell is harmless.

While thinking about this column, I wrote down my top smells. I include, in no particular order, coffee, barbecue, vanilla, a freshly cleaned house (Clorox?), chocolate, bacon, gasoline (I like cars) and rain. I associate rain with golf courses.

Spring rain or thunderstorms have a distinct smell or scent. This smell is known as petrichor. The word is constructed from the Greek word petra, meaning stone, and īchōr, which means the fluid that flows from the veins of gods. In rural and wooded areas, this smell is produced by the actinomycetes, bacteria that produce something like filamentous hyphae. The rain kicks up the spores produced by the bacteria, and they float to your nose like an aerosol. The smell is rather sweet, as captured by playwright Estela Portillo Trambley: “The smell of rain is rich with life.”

Rain that is more acidic produces a different smell. In urban environments, rain tends to be more acidic than normal. Acidic rain hitting organic debris or chemicals on the ground releases minerals that react with chemicals lying on a surface, like gasoline. I would describe this smell using an Eva Wolfe quote, “I know the Devil; he’s an illuminated rebel and he smells like rain.” Rain is probably the most quotable smell.

Golf courses contribute to the beauty, functionality and recreation of a landscape. Often overlooked, however, is the contribution made to our sensory inputs.