A large contingent of students and staff was gathered when I arrived for my volunteer shift at the Conservatory Greenhouse at the University of Minnesota on the St. Paul campus. The crowd was on hand to help with the gentle felling of the largest plant in the greenhouse, decades old and 30+ feet tall.
Native to the island of New Caledonia in the South Pacific, this fern -- Sphaeropteris intermedia the largest of all tree ferns -- has been happily growing in the tropical room of the greenhouse for a number of years, to the point its fronds are brushing up against the glass ceiling panes of the roof.
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| Tree fern fronds brushing against the roof of the U of M greenhouse |
Rather than cut the tree down and lose the specimen, the staff decided to try to save the tree. The process would involve cutting off the top half of the tree and reinserting it into a new space in the soil of the greenhouse floor.
Months of planning and preparation
A well-known technique was used, referred to as air-layering, where a collar of moss was attached around the trunk at the midsection. The moss would be attached only after first wounding the bark to encourage new roots to grow into the moss (weeks to months). Then the next steps may occur in rapid succession:
- the canopy of fronds would be significantly reduced in number to match the capacity of the new roots to deliver water and nutrients;
- the trunk would be completely sawed through once the new roots had been established in the root ball;
- the top half of the tree, with its new root ball, would be carried to a new spot in the soil of the tropical room floor.
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| Moss collar into which new roots grow (air-layering) |
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| The canopy is reduced to match the root ball capacity |
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| Sawing through the tree trunk just below the new root ball |
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| The tree was felled gently onto our shoulders, me in the middle on the right (photo courtesy of Adam Wegren) |
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| The new root ball is firmly planted in the new location |
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| The old tree stump will be sawed down and reused as a support for orchids |
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| Making final adjustments to the new, shorter, tree fern |
University of Minnesota Conservatory
The
greenhouse on the St. Paul campus of the U of M is free and open to the public. The greenhouse is divided into two sections. The public section may be viewed free of charge during regular business hours during the week. To view the non-public collection, arrangements may be made with the staff for a private tour, also free of charge (donations are accepted).
Food of the dinosaurs
Tree ferns have existed on Earth since the age of the dinosaurs, more than 200 million years during the Jurassic period. With respect to other types of plants ferns predate flowering plants and conifers. Only mosses are older than ferns. Currently, there are 25 genera of tree ferns, with hundreds of species. Their range limited to subtropical rain forests of the Americas, Pacific Islands, New Zealand, and Australia.
My personal experience with tree ferns
A few times over the years I've had the privilege of hiking past tree ferns. Given their size and exotic appearance, I couldn't help but stop and stare at them. In one respect, the fronds look like any other that ferns spread across the forest floor, but the tree ferns tower overhead, rising on serious trunks. And, their eye-catching golden fiddleheads can be massive, larger than my own head. On the big island of Hawaii, there is an actual tree fern forest in Volcanoes National Park. And, I have vivid memories of hiking through fern-canopied trails of New Zealand, suffused with gentle green light. Magic.
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| Tree fern canopy, New Zealand |
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| Dappled green shadows underfoot on the trail, New Zealand |
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| Mesmerizing tree fern pattern on the forest floor |
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| Hiking through a tree fern forest, New Zealand (photo courtesy of Tom Wilson) |
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| Unfurling golden fiddleheads, Hawaii Volcanoes National Park |
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