Monday, August 17, 2020

Nepeta and Bumblebees

In front of our garage is a large stone planter, about 6’X10’, stuffed full with lovely, fragrant Nepeta (Catmint). In late spring, at the height of flowering, the bumblebees are so numerous that the planter practically vibrates with the humming of little bee wings. I find myself enthralled watching the bees industriously moving from bloom to bloom and plant to plant. The urge to reach out and pet the fuzzy striped bodies is nearly irresistible. They seem completely oblivious to my presence. 

Several years ago, however, the bees weren’t there. Maybe a stray or two, but that was it. Much has been made of the decline of honeybee populations, but surely that couldn’t be the same thing as what was happening to my bumbles. Could it? I wracked my brain trying to remember if I or my husband used any of the 'bad' chemicals lately. And I glared in my neighbor's direction because I just knew he prioritized a big green lawn over a pollinator-friendly habitat.

Around that time, I began to read snippets in the news about a growing mismatch between biological events of pollinators and their favorite host plants. This was referred to as phenological mismatch. (See definition below). The general hypothesis is that climate change is contributing to this phenomenon, and related scientific research is being conducted worldwide.

The main theory is that the plant, like my Nepeta, uses mean daily temperature as its phenological cue to break dormancy and flower, while the pollinator, like my bumbles, uses day length. If these two species depend on their interaction with one another for pollination and food, the changing environment means they may end up missing each other entirely. Of course, an occasional occurrence of early spring isn’t going to decimate bumblebees. But if this is a permanent shift….

Because I love my garden and the birds, butterflies, and bees that occupy it, I worry. I worry enough that I included a reference to phenological mismatch early in my book, Guardians of Grace, as one of the subtle clues of climate chaos to come.

Of course, my characters don’t know this. They, like me, are just wondering why the Nepeta is blooming so early, and why the bumblebees are missing out on the nectar.

According to a quick internet search, Phenology is the study of the timing of the biological events in plants and animals such as flowering, leafing, hibernation, reproduction, and migration. Scientists who study phenology are interested in the timing of such biological events in relation to changes in season and climate.





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