Tuesday, November 14, 2023

Dawn Redwood (Metasequoia) in Massachusetts

Arnold Arboretum metasequoia
Metasequoia, species name Metasequoia glyptostroboides, is also commonly known as dawn redwood species, It is related to the North American redwood and sequoia trees, but native to China. While shorter than its relatives, metasequoia is fast-growing, and known to potentially exceed 150 feet in height under idea growing conditions. Many 20 year old trees have reached 50-60 feet in height. Unlike its relatives, it sheds its needles in fall and grows anew in spring. Also unlike its North American relatives, metassequoia is winter-hardy, and has been successfully grown across New England. 

Roughly 65 million years ago, metasequoia was widespread across Asia and North America, but then disappeared from the fossil records thereafter, and was thus catagorized as extinct. In the 1940s trees were discovered by botanists in Lichuan, a county in Hubei provernce, east-central China. After a period of species misidentification, in 1948 the trees were formally confirmed as the 'extinct' metasequoia, hence a "living fossil." That same year, the Arnold Arboretum of Harvard University, funded an expedition to collect seeds. The first tree planted at the Arboretum now easily tops 100 feet, and in 1995 was incorporated into the Arboretum's logo. 

Seeds were subsequently distributed to universites around the world. Commercial plant nurseries sell the original species and have developed several cultivars with different attributes, such as dwarf, narrow, weeping, yellow/orange instead of green, and so on.

'Gold Rush' Metasequoia
For the original type, the needles are light green, in the fall turning a pinkish-tan to red-brown and then falling to the ground. Cultivars such as Gold Rush and Amber Glow have yellow/green needles and a mature height of 35-40 feet. The National cultivar tops out at 60 feet and only 20 feet wide. The dwarf cultivars top out at under 20 feet. The species is not considered drought resistant, and especially in early years, the soil should not be allowed to go completely dry. Optimal growth is achieved with full sunlight and damp to wet terrain.

Sadly, in China, the dawn redwood is threatened with slow-motion extinction. A survey of wild-growing trees in the original locations, conducted in 2007-09, counted just under 6,000 trees. There are far more than that number existing outside of China - all planted after 1948. While it is now illegal to cut down or dig up dawn redwoods in China, the demand for seeds is so high that almost all seed-containing cones are collected, leaving no opportunity for new seedlings in the existing groves. The existing trees had diameters up to five feet and some exceeded 150 feet in height. Age was estimated as up to 265 years. Stumps of trees cut prior to protection indicate that these trees can survive close to 400 years, approach 200 feet in height and eight feet in diameter. While huge compared to most other tree species, those are smaller numbers seen for the American sequoia and redwood species. Those can exceed 300 feet in height, 25 feet in diameter, and 2,000 years in age.

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