![\"Lichen](\"http:\/\/blogs.northcountrypublicradio.org\/allin\/files\/2015\/11\/lichenonbirch.jpg\")
<\/a>Lichen on a dead birch. Lichen is not the killer in this movie. It just discovered the body. Photo: Eli Sagor<\/a>, Creative Commons, some rights reserved<\/p><\/div>\n The truth is it\u2019s very rare for an insect or pathogen to be the sole reason for a tree\u2019s demise, and unusual for a single agent to be even a primary cause. Those guys are just there cleaning up or possibly just passing through. But dang, they sure look guilty as heck, don\u2019t they? Unfortunately the \u201cwrong place at the wrong time\u201d defense is useless most of the time.<\/p>\n One common observation I hear about a declining tree is that as branches die, tufts of \u201cmoss\u201d is seen accumulating on them. A dead spruce is festooned tip to root with the greenish fuzz. Maple trunks sport a crusty version of this stuff. Obviously, \u201cmoss\u201d is evil and it kills trees, right?<\/p>\n Although it can look like moss, the \u201cguilty by association\u201d organism is called a lichen. It thrives on just about anything left out in the weather long enough. Lichens are as happy living on rocks and old lumber piles as on a tree branch, and they don’t kill those things. I\u2019m fairly sure anyway.<\/p>\n Mistletoe and dodder are plant parasites that freeload off trees and other plants by siphoning off sugars made by their hosts. But believe it or not, lichens are harmless. The reason they don’t hurt trees is they make their own food. It\u2019s not a plant, but it photosynthesizes\u2014how does that work?<\/p>\n Cross section of lichen, which is an organism in a symbiotic relationship between green algae and fungus. 1. Thick layers of fungal hyphae, called the cortex 2. Green algae 3. Loosely packed hyphae 4. Anchoring hyphae called rhizines. Diagram: JDurant<\/a>, Creative Commons, some rights reserved<\/p><\/div>\n It seems lichen is a kind of mutt. I\u2019m not sure if it comes from its mother\u2019s or dad\u2019s side, but lichen is half algae. As we know, algae has chlorophyll and makes its own food from sunlight, but needs a moist place to hang out. It won\u2019t last long on a rock or tree branch.<\/p>\n The other half of lichen\u2019s family, um, tree is a fungus, which is good at holding moisture but which can\u2019t make its food. Somewhere along the line these two made a business deal. Alice Algae and Freddie Fungus took a lichen to each other, as my Biology teacher said. It\u2019s one of those symbiotic relationships wherein both parties benefit equally. A handy arrangement, although not legally binding in most states.<\/p>\n So how come lichens appear as a tree dies back? Plants and lichens both need sunlight. A healthy branch packed with foliage out-competes lichens and restricts their access to light–this keeps them small. As a branch declines, foliage thins out and lets in more sun, and lichens grow tremendously. They\u2019re victims of circumstance.<\/p>\n This dynamic can be seen on a small scale each fall after deciduous trees shed their leaves. Over the winter lichens grow slightly and expand when daytime temperatures go above freezing. In the spring, they shrink back as leaves again overtake them.<\/p>\n When something looks obvious you may feel silly looking for other causes. I mean, it\u2019s pretty far-fetched to think the kid with the bat isn\u2019t the guilty one. What are the chances it\u2019s a ploy to get you out in the open so aliens can abduct you? (I\u2019m guessing small, but that\u2019s not my area of expertise.)<\/p>\n But when a favorite tree appears to be consumed by \u201cmoss\u201d don\u2019t be fooled. Lichen or not, things are not always as they appear.<\/p>\n<\/a>
![JDurant<\/a>, Creative Commons, some rights reserved<\/p><\/div>\nIt seems lichen is a kind of mutt. I\u2019m not sure if it comes from its mother\u2019s or dad\u2019s side, but lichen is half algae. As we know, algae has chlorophyll and makes its own food from sunlight, but needs a moist place to hang out. It won\u2019t last long on a rock or tree branch.<\/p>\nThe other half of lichen\u2019s family, um, tree is a fungus, which is good at holding moisture but which can\u2019t make its food. Somewhere along the line these two made a business deal. Alice Algae and Freddie Fungus took a lichen to each other, as my Biology teacher said. It\u2019s one of those symbiotic relationships wherein both parties benefit equally. A handy arrangement, although not legally binding in most states.<\/p>\nSo how come lichens appear as a tree dies back? Plants and lichens both need sunlight. A healthy branch packed with foliage out-competes lichens and restricts their access to light–this keeps them small. As a branch declines, foliage thins out and lets in more sun, and lichens grow tremendously. They\u2019re victims of circumstance.<\/p>\nThis dynamic can be seen on a small scale each fall after deciduous trees shed their leaves. Over the winter lichens grow slightly and expand when daytime temperatures go above freezing. In the spring, they shrink back as leaves again overtake them.<\/p>\nWhen something looks obvious you may feel silly looking for other causes. I mean, it\u2019s pretty far-fetched to think the kid with the bat isn\u2019t the guilty one. What are the chances it\u2019s a ploy to get you out in the open so aliens can abduct you? (I\u2019m guessing small, but that\u2019s not my area of expertise.)<\/p>\nBut when a favorite tree appears to be consumed by \u201cmoss\u201d don\u2019t be fooled. Lichen or not, things are not always as they appear.<\/p>\nPaul Hetzler is a horticulture and natural resources educator with Cornell Cooperative Extension of St. Lawrence County<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"We all know correlation does not equal causation, and that it\u2019s unfair to convict someone […]<\/p>\n","protected":false},"author":102,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[4880,15765,99,15766],"_links":{"self":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/15554"}],"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=15554"}],"version-history":[{"count":5,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/15554\/revisions"}],"predecessor-version":[{"id":15573,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/posts\/15554\/revisions\/15573"}],"wp:attachment":[{"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/media?parent=15554"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/categories?post=15554"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.northcountrypublicradio.org\/allin\/wp-json\/wp\/v2\/tags?post=15554"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}](\"https:\/\/commons.wikimedia.org\/wiki\/File:Lichen_Cross_Section_Diagram.svg\"){kind=link}