Nature Notes

Keeping Cool

By Sydney Chandler

Wowzer, it’s hot out! A recent hot summer day at the Arboretum consisted of beaming sunshine, cloudless skies, minimal breeze, and temperatures around 90°F. Plants, animals, and visitors to the Arboretum all need strategies for surviving these sweltering temperatures.


As visitors, we don sunscreen, sun hats, and protective clothing. While plants need the sun for survival, they too protect themselves from the harsh UV radiation with a group of molecules called sinapate esters. Without these molecules, plants could suffer damage to DNA and reduced growth. While protecting themselves, plants also provide shade for other animals.

OLYMPUS DIGITAL CAMERAHosta Shade (‘Royal Standard’)

On these hot days, small mammals have an advantage: their high surface-to-mass ratio means that they radiate heat more efficiently. Their primary goals are to keep their bodies cool and to avoid water loss. For many, the cool shade under the Arboretum’s giant oak trees or under the dense hosta leaves are a great respite from the heat.


The coolest spaces this weekend included the Japanese Garden, under the crabapple trees, on the damp trails adjacent the Heron Pond, and by the waterfall. As humans, we get to sweat to cool our bodies via evaporation. However, our small mammal neighbors at the Arboretum don’t sweat like us. Instead, we can spot rabbits lying against the cool sandy Ridge Trail, squirrels using the blonde undersides of their tails as reflective umbrellas, animals licking themselves to cool via evaporation, and reduced activity throughout the grounds to conserve energy.


Just like us, plants and animals have different strategies to survive the heat. Luckily, the Arboretum has ample sources of shade and water to help make a sweltering day more enjoyable.

Sydney Chandler is a Minnesota Master Naturalist Volunteer.

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