Window Ferns and Frost Flowers: The sublime beauty of winter

You have to admit it takes a special kind of person to find the sepia lining in a sunburst. So do you mind if I complain about energy-efficient windows for a minute?

Back in “the day,” homes used to leak much heat through their windows. The thermal resistance, or insulation value, of a material is measured in “R-value” units. An inch of plywood rates an R-value of roughly one, for example, while an inch of foil-faced foam board has an R-value of 7.2.

For homes in northern NY State, the US Department of Energy recommends a minimum R-value of 20 in exterior walls. A single pane of window glass, though, has an R-value of 0.07. You can see why glass can be a serious “energy nosebleed.” Most new construction these days employs double or even triple-pane windows. To make them even more efficient, some high-end window units have inert gas between panes and/or special coatings.

So big deal, houses are warmer now and require less gas and oil to heat. Whoopee. They’re missing out on the magic of window ferns.

If there’s one redeeming feature of single-pane glass (and there may only be one), it’s that on a cold winter morning you wake up to an exquisite, freshly sculpted work of art etched on every window. Water vapor inside the home condenses and freezes onto cold glass in complex fractal patterns resembling ferns, flowers or trees. Ice nucleates onto a window in different ways depending on how smooth the glass is, and even what kind of dirt or dust is on it.

Fractals are naturally occurring, repeated patterns that we see in such things as snowflakes, ocean waves, peacock feathers, lightning bolts and sea shells. People with a lot more math acumen than I have spend decades studying fractals and writing equations to describe them. All I know is that those patterns are breathtaking. But maybe that’s the cold mornings I’m thinking of.

Another “plant” in winter’s garden is the frost flower. You may have seen masses of cottony ice filaments pushed out of a water-soaked log in the woods. My kids used to be fascinated by the frost flowers that sprouted on frigid March mornings from a patch of wet earth behind our house. Technically, frost is from condensed water vapor, so it’s more accurate, if less alliterative, to call these ice flowers.

Calling attention to hoar frost runs the risk of having to suddenly explain oneself. The Old English word for grizzled, hoar, is used to describe the gossamer ice crystals that festoon every subfreezing surface that contacts a humid air mass. During a cold snap, intricate ice feathers grow on branches, twigs and grasses along an unfrozen river or rushing brook, and are the subjects of many pictures.

Some of world-renowned artist Andy Goldsworthy’s sculptures are meant to be ephemeral. Works created from grasses, twigs or ice are left to efface in the elements. This of course happens with natural works of art. As the woodstove heats up, window ferns melt. Frost flowers wilt as the sun comes out.

But even if you took some of the more striking ice-art into a deep freeze, they’d disappear. Ice sublimates; that is, it evaporates directly from a solid to a gas without needing to first become liquid. Frozen laundry dries as ice crystals sublimate. This happens faster in low humidity.

I hope everyone has the chance, at least once, to experience the sublime beauty of window ferns. And after that, the deep appreciation of a warm, energy-efficient home.

Paul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County