The World According to Fungi

From slimy to friendly, these invaders live in symbiosis with plants—and us.

By Gordon Grice
Jun 18, 2008 5:00 AMJul 13, 2023 4:02 PM

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The lingering death of a tree in my backyard has me thinking. The Eastern red cedar looked bad—shaggy, wasted, a dandruff of gray decline mixed in with the healthier bluish-green needles. We had seen the cause already, in the form of little spiky galls hanging here and there like drab Christmas ornaments. Each of these ornaments was smaller than a golf ball and seemingly made of wood, which might make you think it was some healthy part of the tree. I picked one off. Each small spike was a spout: a hole surrounded by a sharp woody projection. The ball resisted pressure only as much as a fruit might. Carrying it to the cement walk, I crushed it under my heel. It wasn’t difficult. Inside, the thing was pulpy and fibrous, its strands of vegetable matter radiating from a tight core. Its wet texture was like that of the new wood you can find under a tree’s bark.

I knew this, from books and such, as cedar-apple rust, a parasite with a provocative life cycle that requires it to jump between juniper and apple hosts. (The Eastern red cedar, despite its name, is actually a juniper.) On the leaves and fruit of apple trees, this parasite manifests itself as leathery spots of discoloration. On junipers it appears as these woody galls. The apple and juniper forms of the parasite are different stages of a single life cycle that involves both sexual and asexual spores.

To look at it, though, I wouldn’t have recognized this sphere as alien to the tree, made as it was of the tree’s own tissues. The tree itself makes the gall, acting on instructions from the fungus, like an animal whose rogue cells produce a tumorous mass.

Rain revealed more. It rained for two or three days—a steady, soaking rain that had my sons whooping barefoot on the lawn. They were all excitement. “The parasite opened up!” they told me. Indeed. All over the 50-foot tree, the galls had effloresced. Through each spiky spout a vivid orange tentacle projected. It seemed as if the tree had collided with a swarm of sea anemones. I bent a bough down so the boys could take a closer look. My oldest son poked at one and proclaimed it slimy. I tried its texture myself: wet gummy worms. Our gentlest touches marred them. I almost expected them to recoil.

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