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Gardening From Alaska

...hoar frost
by Jeff Lowenfels
by Jeff Lowenfels


Jeff is the Past President of the Garden Writers of America, a columnist with the Anchorage Daily News, Host Alaska Gardens and Supporter of Plant a Row.

October 22, 2006

When Outsiders ask me what I grow in my Alaskan garden, I invariably give them one of those standard wise guy, ha-ha, Alaskan lines we all have. This one is answered with: ‘snow peas, iceberg lettuce and snowball cauliflower. “ Ta dum.

It usually takes a few seconds for them to realize that I am sort of joking. It isn’t all ice and snow up here. Then there is the smile along with inevitable the groan (from the my wife who has heard this a million times, if not from the Outsider).

I really should add “hoar frost” to the list of reliable crops we can grow in Alaska. You would only have had to be here earlier this week to understand that when a coating of brilliant white hoar frost hits, it makes even the bleakest yard a wonderland and does the job as well as any carpet of summer flowers.

Hoar frost forms because air can only hold so much water vapor and air is able to hold less water as temperatures drop. At some point, water literally falls out of suspension in the air. If temperatures are above freezing at this point, water condensation, what we gardeners call “dew”, forms on any available surface.

If temperatures are below freezing when water reaches this dew point, the water vapor turns into ice crystals forming a frost instead of a dew. Cold surfaces are coated and the coating attracts additional water.

No flowering vine you could plant here could decorate a chain link fence with the speed or elegance of an evening of good hard hoar frost. Not even the fast growing and magnificent humulus lupulus (hops) nor a the lovely Clematis tangutica with its multitude of small yellow flowers and resulting fluffy seed heads can come close.

With hoar frost, the backyard swing set becomes a bridal arbor, the trampoline, a Venetian ice sculpture. If ever there was a use for a tree, it is to catch and hold on to hoar frost. Nothing is plain. Everything looks wonderful. Literally.

Hoar frost makes the garden bloom again. The ligularia and delphinium stalks become swords of light in the afternoon sun. Those pesky campanula’s I considered weeds become delicate ice ornaments, my own equivalent of Harvard’s Glass Flowers.

The hoar frost washes away the awful color of the new birdfeeder that hasn’t had time to weather (and that alone shows its power). Best of all, a hoar frost can make an already amazing blue winter Alaskan sky look even bluer. It produces an effect that can’t be beat by any Harry Potter movie or Martha Stewart set.

Spent raspberry canes, denuded birch, hated cottonwoods and flowering shrubs all come back to life under the uniform cover of a hoar frost. The ice crystals that form, however, don’t always take the same shape. Sometimes, depending on the temperature and the wind, the ice crystals take the shape or needles. Other hoar frosts produce crystals with fern patterns or in the shape of tiny blades or even feathers.

Every year, when the first few hoar frosts touch down, the strands of formerly invisible spider webs are among surfaces that catch the frost crystals. They are there all summer long and we don’t see them. Some summer sights only winter can reveal.

It is worth taking the time to examine the hoar frost growths in your yard and garden and around town. Each is different and each is a reason to get outside and see some of Nature’s glory. Things still happen out there when the temperatures are below freezing.

Oh, and by the way, hoar frost can sometimes become a problem which is another reason to keep an eye on it. If too many crystals accumulate and grow, their weight can pull down branches, especially shrubs’. As pretty as it might be, you have to be ready to knock it off to save life and limb, as it were.

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