As I stepped out of my truck last night around 9pm, after attending a Cub Scout event with my son, I looked up to the sky above our house. The deep, clear blackness of the sky was spotted with stars, highlighted by Orion’s Belt in the southern sky. Winter skies like this almost always precede colder mornings, as earth’s heat isn’t held in by cloud cover.
What I hadn’t expected was the brilliant hoar frost that covered nearly every branch, bud and stem standing in our neighborhood. We will normally get a few of these frosts each winter, when the world looks like it’s been dipped and frozen in confectioner’s sugar. A hoar frost (a type of radiation frost) requires the combination of freezing temperatures, low winds, atmospheric moisture near the surface (often in the form of fog), and clear skies.1 When the clear skies allow the plants and other surfaces to cool more quickly that the surrounding air, the moisture crystallizes in a thick, hairy frost.
Every branch of the trees and shrubs in our backyard held a thick coating of frost. As the morning progressed, the a light wind picked up, each breeze bringing a shower of frost crystals through the air.
Bright blue skies formed a sharp contrast to the frost-covered branches of our crabapple.
The dried stems and seed heads of perennials took on a fuzzy appearance as well.
The frost crystals were so light, even wispy stems of Pennisetum alopecuroides ‘Hameln’ were dusted from the ground up.
The seed pods of sweet gum (Liquidambar styraciflua) are one of my favorite frost and snow catchers in the landscape.
The frost holds on even to the tip of each sweet gum bud. Of all its seasons of beauty, winter is perhaps my favorite for the sweetgum. There’s something about their bark, seed pods and buds that accessorize well with the frost, ice and snow of winter.
Not even icicles were spared a fresh coating of frost, as here on a Clematis ‘Rouge Cardinal’.
Our Pinus mugo in the front border appeared painted with a thin coating of frost. The evergreens were less coated with the hoar frost, perhaps because they retained their heat better than the dormant plants.
The small boxwood we planted last fall looked like a new variegated cultivar, with frost decorating the outer edge of each leaf.
Vertical surfaces, like this Knock Out Rose cane, avoided the frost, but the rose thorns held a few crystals each.
Our 30 ft sugar maple (Acer saccharum) in the south side yard was brilliant against the blue sky, but its russet buds covered in frost were one of the most striking views.
Frost crystals stood at attention on most of the vines in the yard, like this Clematis terniflora (sweetautum clematis).
As I sit here mid-afternoon writing this, the frost has released its grip, blown by a light breeze and melted by the sun. The temperature, which hovered in single digits this morning, has quickly risen to 24 F. Photos and memory remain the only evidence the dreamlike-world painted by the frost even existed.
Although this is the time of year when gardeners begin to pine for spring, natural gifts like this morning’s help to bring our focus back to the beauty and wonder of today.