Sunday, March 29, 2015

Delicate Endurance

Sharp-Lobed Hepatica (Hepatica acutiloba)
this morning after a cold night night in the hollow
It was 25º in our forest hollow last night, and yet these Hepaticas seem none the worse for the wear. The temperature had barely returned back above freezing when I snapped this picture (and the one at the bottom of the post) at about 8 o'clock this morning.

People often assume freezing temperatures mean sudden death for wildflowers, but this is not the case. Most spring ephemerals are adapted to the drastic temperature swings of early spring. Of all the wildflowers now blooming, the Hepaticas looked the healthiest this morning after last night's freeze. The Toothworts and Spring Beauties carpeting the forest floor looked droopy, but they were perking up as soon as the sun hit them. The Hepaticas almost looked normal.

Freezing water is the death of plants. When water freezes in plant tissue, the precious, life-giving fluid becomes dagger-sharp ice crystals, puncturing cell walls, spilling cell contents, and breaking down the leaf's micro-architecture. This, as you can well imagine, is catastrophic for the plant.

Sweet Betsy (Trillium cuneatum) surrounded by a carpet of
Spring Beauty (Claytonia virginica) taken in early April last year.
The Trilliums with their large thick leaves looked like they had suffered this fate this morning. I wish I had taken pictures so you could see before and after (photo at right is from 2014). It seemed like their thick water-filled leaves had been frozen and thawed. Most of them had the look of vegetables blanched too long in boiling water. I assumed these Trilliums would die back and have to wait until next year for another chance at flowering. But I was wrong. To my astonishment, I went back this afternoon and every single Trillium looked fine and healthy as though resurrected. Trilliums truly must have antifreeze in their veins!

Hepatica, on the other hand, has developed a completely different strategy for coping with the harsh weather. It uses last year's leaves to help with an early start. Rather than making its new leaves first, Hepatica relies on last year's leaves that overwinter in the leaf litter. Though worn and tattered, the old leaf takes in the sun on warm late winter days and are pretty much depleted and gone by bloom time. The plant then uses the root-stored food for the energy it needs for flowering in early spring. It is only after the plant has flowered and gone to seed that Hepatica then spends the additional energy to make new leaves that go into the full-time business of photosynthesis. These leaves are adapted to the dim light of the summer forest floor, and they persist through summer, fall, and winter until next spring.

Blooming Hepatica survives late cold snaps as a minimalist. With no leaves to worry about during bloom-time, the Hepatica's secret seems to lie in simplicity and a tendency to live in sheltered places.

Maybe there's a lesson here. Nature reminds us that there is usually more than one way to solve a problem, and sometimes being an oddball has advantages.

Sharp-Lobed Hepatica (Hepatica acutiloba) greets the dawn after a cold night

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