Mistletoe
When Tree Man Mike came to look at the trees in our yard this winter, I asked him about the swelling on the trunk of the cottonwood. In summer the deep woody furrows sprout a ton of little green leaves directly from inside the bark.
I thought these green sprouting bits were the cottonwood trying to regrow new branches at the site of a wound. But even as I considered that, I knew it wasn't right. The sprouting leaves were tiny, glossy, spoon shaped, and nothing like cottonwood leaves, and they were massed all over.
Mike easily identified what was going on. It's mistletoe.
Mistletoe is a parasite. It doesn't grow in the ground with a root system. Instead, seeds lodge in the twigs and bark of trees and then tap into the water and nutrients of the host plant. Mistletoe is a pest that infests forests and landscape trees. Large infestations can eventually kill trees.
In California, in Tom's neighborhood, big balls of evergreen mistletoe hang everywhere in the oak trees and the decline of the infested trees is noticeable. It's a scourge all over the city of Thousand Oaks.
Mistletoe is a rampant pest in northern Europe too. When we took a river cruise down the Seine River a few years ago, we saw balls of mistletoe in the branches of decimated trees all up and down the riverbanks. It looked so bad.
My cottonwood here in Santa Fe doesn't have a ball of mistletoe up high. It's sprouting from low on the trunk, and because I knock off the new leaves all the time, it doesn't grow much. But it can't be eliminated; the plant's feeding structures have gone deep into the living cambium layer of the trunk of the cottonwood.
Mike thinks the mistletoe did not cause the bark wound on the cottonwood trunk. Instead, some kind of disease or injury happened long ago that created a scar, and mistletoe seeds dropped into the cracks and got established.
The only remedy is to keep the shoots of mistletoe from growing much and certainly to keep it from ever setting seeds. The seeds are inside berries that birds eat, and they are very sticky, keeping them from plopping down to the ground, where mistletoe can't grow. Instead, they stick where the birds poop them, in the trees. The name comes from Old English "mistel" meaning bird poop, and "tan" for twig. Birdpoop Twigplant.
In summer I go out every week and strip off the new green growth and I guess I can keep doing that. It's easily reached, the growth is chest high, easy enough to get to, but a pain since there are so many shoots tight inside folds of bark.
Another method is to wrap the trunk in black plastic to deprive the mistletoe of any light -- although it's a parasite using the cottonwood's nutrients to grow, it also does photosynthesize through its green leaves, so killing the leaves off might help.
There are many, many varieties of mistletoe, and I was surprised that several types grow in the desert southwest, infesting palo verde trees and mesquite.
How mistletoe got to be a symbol of Christmas and stolen kisses is a whole story in itself. Really, it's a scourge killing trees in Europe and a terrible pest ruining oaks in California and a big nuisance here on my cottonwood tree.
I thought these green sprouting bits were the cottonwood trying to regrow new branches at the site of a wound. But even as I considered that, I knew it wasn't right. The sprouting leaves were tiny, glossy, spoon shaped, and nothing like cottonwood leaves, and they were massed all over.
Mike easily identified what was going on. It's mistletoe.
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| Mistletoe leaves and branches |
Mistletoe is a parasite. It doesn't grow in the ground with a root system. Instead, seeds lodge in the twigs and bark of trees and then tap into the water and nutrients of the host plant. Mistletoe is a pest that infests forests and landscape trees. Large infestations can eventually kill trees.
In California, in Tom's neighborhood, big balls of evergreen mistletoe hang everywhere in the oak trees and the decline of the infested trees is noticeable. It's a scourge all over the city of Thousand Oaks.
 |
| View from Tom's back hillside terrace -- the oak trees next to the palms are infested with balls of mistletoe that are killing them. |
Mistletoe is a rampant pest in northern Europe too. When we took a river cruise down the Seine River a few years ago, we saw balls of mistletoe in the branches of decimated trees all up and down the riverbanks. It looked so bad.
My cottonwood here in Santa Fe doesn't have a ball of mistletoe up high. It's sprouting from low on the trunk, and because I knock off the new leaves all the time, it doesn't grow much. But it can't be eliminated; the plant's feeding structures have gone deep into the living cambium layer of the trunk of the cottonwood.
Mike thinks the mistletoe did not cause the bark wound on the cottonwood trunk. Instead, some kind of disease or injury happened long ago that created a scar, and mistletoe seeds dropped into the cracks and got established.
The only remedy is to keep the shoots of mistletoe from growing much and certainly to keep it from ever setting seeds. The seeds are inside berries that birds eat, and they are very sticky, keeping them from plopping down to the ground, where mistletoe can't grow. Instead, they stick where the birds poop them, in the trees. The name comes from Old English "mistel" meaning bird poop, and "tan" for twig. Birdpoop Twigplant.
In summer I go out every week and strip off the new green growth and I guess I can keep doing that. It's easily reached, the growth is chest high, easy enough to get to, but a pain since there are so many shoots tight inside folds of bark.
Another method is to wrap the trunk in black plastic to deprive the mistletoe of any light -- although it's a parasite using the cottonwood's nutrients to grow, it also does photosynthesize through its green leaves, so killing the leaves off might help.
There are many, many varieties of mistletoe, and I was surprised that several types grow in the desert southwest, infesting palo verde trees and mesquite.
How mistletoe got to be a symbol of Christmas and stolen kisses is a whole story in itself. Really, it's a scourge killing trees in Europe and a terrible pest ruining oaks in California and a big nuisance here on my cottonwood tree.
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