{"id":13497,"date":"2015-02-08T09:00:51","date_gmt":"2015-02-08T14:00:51","guid":{"rendered":"http:\/\/blogs.northcountrypublicradio.org\/allin\/?p=13497"},"modified":"2015-02-08T09:38:45","modified_gmt":"2015-02-08T14:38:45","slug":"freeze-pops-exploding-the-exploding-tree-myth","status":"publish","type":"post","link":"https:\/\/blogs.northcountrypublicradio.org\/allin\/2015\/02\/08\/freeze-pops-exploding-the-exploding-tree-myth\/","title":{"rendered":"Freeze pops: exploding the exploding tree myth"},"content":{"rendered":"
\"Frost<\/a>

Frost crack on large red maple. Photo: Eli Sagor<\/a>, Creative Commons, some rights reserved<\/p><\/div>\n

When temperatures dip well below zero Fahrenheit, especially if they fall precipitously, things pop. Wood siding creaks. Frozen lakes and ponds emit ominous groans, snaps and booms that reverberate through the ice. If soil moisture is high and frost is deep, even the earth can shift in a harmless localized cryoseism<\/i>, or \u201cfrost quake\u201d that produces a nerve-rattling bang.<\/p>\n

If you live in a wooded area, you\u2019ve probably heard trees popping and cracking during a deep freeze. It\u2019s an eerie sound on an otherwise still night. Native peoples from northern regions were very familiar with this sound, and some even named a winter month in honor of it. The Lakota call February cannapopa wi<\/i>, \u201cmoon when trees crack from the cold.\u201d The Arapaho consider December the tree-cracking time; for the Abenaki, it\u2019s January.<\/p>\n

I once found a reference in a novel to exploding trees. In the book, a lost teen boy survives a northern winter that\u2019s so cold, trees explode into smithereens as if dynamited. I\u2019d lived through winters with minus-40 temperatures but had neither seen nor heard of exploded trees. What did this author know that I didn\u2019t?<\/p>\n

After much research, I discovered that fiction is sometimes, well, fictional. As I thought, trees don\u2019t blast themselves to bits. But since that first reference I\u2019ve encountered the exploding-tree myth a number of times. So what does happen when trees go \u2018pop\u2019 in the night (or day)?<\/p>\n

As we all know, when water freezes, it expands. Some \u201cfreeze pops\u201d happen when water that collects between narrow-angle trunk unions freezes.<\/p>\n

Luckily, sap is not pure water. It\u2019s endowed with antifreeze in the form of sugars, and to a small extent, dissolved minerals. The more sugar (or any solute) that\u2019s mixed with water, the lower the freezing point becomes. This is due to something known as the \u201cColligative Property of Solutions,\u201d as you no doubt recall from General Chemistry. (Actually it\u2019s just as well to forget such trivia, which gets in the way of remembering where you put the car keys.)<\/p>\n

There comes a point when even sugar-fortified sap will freeze and expand. This can sometimes rupture the bark of a tree, resulting in a visible crack as well as an audible one. In many cases frost cracks close with no long-term ill effects, but sometimes they become perennial. Rarely, a frost crack does send a piece of bark flying. This would tend to happen with a tree like trembling or big-tooth aspen.<\/p>\n

Since it\u2019s a weak point, a previous frost crack may pop open again in cold spells. Then each spring and summer the tree makes callus (\u201crepair\u201d) tissue in an attempt to cover the injury, resulting in a raised lip along the seam. Such trees have reduced timber value and an increased potential for decay to set in.<\/p>\n

There\u2019s nothing one can do for frost-cracked forest trees in terms of prevention or treatment. You can protect young landscape and fruit trees, however, with light-colored trunk wraps, or even a coat of interior-grade white latex paint, on the lower trunks. Wraps should be removed promptly in spring, and cracks or wounds should never be coated.<\/p>\n

In truth, trees do explode occasionally\u2014if someone has placed explosives in them. A friend of mine contracted with the US Forest Service in Oregon in the 1980s to make habitat for cavity-nesting birds. To create snags, he climbed live mature spruces and firs, drilled a hole in the trunk halfway up and inserted dynamite, which he detonated from a safe distance. I\u2019m pretty sure he did this work when it was not below zero.<\/p>\n

Paul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County <\/i><\/p>\n","protected":false},"excerpt":{"rendered":"

When temperatures dip well below zero Fahrenheit, especially if they fall precipitously, things pop. Wood […]<\/p>\n","protected":false},"author":102,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/13497"}],"collection":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/users\/102"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/comments?post=13497"}],"version-history":[{"count":7,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/13497\/revisions"}],"predecessor-version":[{"id":13514,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/13497\/revisions\/13514"}],"wp:attachment":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/media?parent=13497"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/categories?post=13497"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/tags?post=13497"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}