Thuja occidentalis, L. in the family Cupressaceae is the Eastern (aka Northern) White Cedar, also known as the Tree of Life or Arbor-vitae. I was really pleased to find one or two small trees, possibly cultivars, at the top end of Cobtree Manor Park, and also somehow or other realised that they might not be the Western Red Cedar, Thuja plicata, that I am much more generally familiar with. I think it was the appearance of the cones that I was suspicious of. They were clearly very like plicata, in their upturned vase shape, but there was still something different.
On checking the tree books and websites, one ID difference between occidentalis and plicata is that occidentalis perhaps has a greater multitude of cones and also that they are terminal on the shoots. I believe the shapes are slightly different as well.
Thuja occidentalis is a rather rarely seen tree in the UK apparently according to the Collins book - so well done Cobtree Manor for planting it! This tree had good numbers of woody female cones that had developed over the year, together with what looked like the browning remains of the male cones (it is monoecious like many conifers), at the tips of many other shoots. By shaking the collected shoots, I obtained a few seeds.
It is native to the eastern Canada and much of the northeastern, northcentral, and east central United States. It was, as far as we know, the first North American tree to be brought to Europe in 1556 (Queen Elizabeth was only three years old at the time) by Jacques Cartier, a French explorer who discovered from the Iroquoian tribe that the boiled leaves made a great cure for scurvy. This saved his expedition from perhaps being wiped out and he called it a miracle, famously naming the tree the "Tree of Life, or Arbor-vitae".
It is also a sacred tree to the Ojibwe tribe, being one of the four plants on its sacred tree. It is the preferred structural element for birchbark canoes, and is still used for poles, shingles and making log cabins. It is grown commercially as a forestry tree, one of its big advantages being its resistance to rot and pests. It's essential oil also has many varied uses.
Its import to Europe is perhaps how Linnaeus was able to name it in 1753, but I don't know whether Linnaeus received specimens from the Americas as well as Europe - I don't see why not. The herbal effects of Thuja must be considered in light of its content of Thujone, a psychotropic and somewhat toxic chemical that is found in a range of conifers, mugwort and sage, and was, apparently mistakenly, originally stated to be the explanation of the chronically toxic effects of absinthe.
The leaves are only moderately distinctive. The upper side is a slightly glossy mid-green with a hint of the suggested (by the standard sources) yellowish green, while the lower side is definitely a distinctly paler but fairly uniform slightly yellowish green. The upper and lower ranks of leaves are very flattened, the upper ones having quite obvious translucent spots half way or more up the leaves. The lateral ranks of leaves are, by contrast, strongly keeled and sharply folded in half over the side of the shoots, with tips incurved to the shoot.
The green of the young shoots then abruptly changes into the red brown of the older twigs, but still with old red-brown scale leaves remaining. According to the books the bluntly tipped scale-like leaves of the lateral shoots are replaced by sharper, more lanceolate leaves on the leading shoots.
The female cones have 4 - 6 pairs of scales, only 2 inner pairs being fertile. The cones are typical Thuja goblet-shaped cups, but in this species the rounded scales have slightly mucronate tips. The individual seeds were also found, about 6 mm long, with their membranous wings giving an overall oval shape.
Thuja occidentalis has a fair number of cultivars (over 300), and is quite popular in cultivation . One of the most famous cultivars is Thuja occidentalis 'Rheingold', certainly a very familiar name to me. The cultivars seem to thrive, and I imagine there are many more individual specimens of cultivars grown than there are live trees of the original species. Oddly enough the RHS suggests growing 'Rheingold' in moist but well-drained soil, apart from that not being too fussy about the type of soil. They also warn that skin contact may cause irritation. 'Smaragd' is a neat narrow green column that is also very popular, as an accent or in hedging.
The ecology of the tree in the wild seems to be focussed on wet, but perhaps not completely marshy soils, and also poor alkaline or cliff-face soils where competition from other trees is reduced. On the poor dry soils it apparently doesn't "perform" in garden terms, but can persist, hanging on by its fingerprints. Such trees are likely to be include some of the oldest trees in Canada and NE USA. This is also one of the most frost-resistant trees, once having been frost-hardened, being able to withstand liquid N temperatures
References:
Illinois Wild Flowers, http://www.illinoiswildflowers.info/trees/plants/white_cedar.html, accessed 24th October, 2014.
The Gymnosperm database. http://www.conifers.org/cu/Thuja_occidentalis.php, accessed 24th October, 2014.
USDA Forestry Service. http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/thuja/occidentalis.htm, accessed 25th October, 2014.
On checking the tree books and websites, one ID difference between occidentalis and plicata is that occidentalis perhaps has a greater multitude of cones and also that they are terminal on the shoots. I believe the shapes are slightly different as well.
Thuja occidentalis is a rather rarely seen tree in the UK apparently according to the Collins book - so well done Cobtree Manor for planting it! This tree had good numbers of woody female cones that had developed over the year, together with what looked like the browning remains of the male cones (it is monoecious like many conifers), at the tips of many other shoots. By shaking the collected shoots, I obtained a few seeds.
It is native to the eastern Canada and much of the northeastern, northcentral, and east central United States. It was, as far as we know, the first North American tree to be brought to Europe in 1556 (Queen Elizabeth was only three years old at the time) by Jacques Cartier, a French explorer who discovered from the Iroquoian tribe that the boiled leaves made a great cure for scurvy. This saved his expedition from perhaps being wiped out and he called it a miracle, famously naming the tree the "Tree of Life, or Arbor-vitae".
It is also a sacred tree to the Ojibwe tribe, being one of the four plants on its sacred tree. It is the preferred structural element for birchbark canoes, and is still used for poles, shingles and making log cabins. It is grown commercially as a forestry tree, one of its big advantages being its resistance to rot and pests. It's essential oil also has many varied uses.
Its import to Europe is perhaps how Linnaeus was able to name it in 1753, but I don't know whether Linnaeus received specimens from the Americas as well as Europe - I don't see why not. The herbal effects of Thuja must be considered in light of its content of Thujone, a psychotropic and somewhat toxic chemical that is found in a range of conifers, mugwort and sage, and was, apparently mistakenly, originally stated to be the explanation of the chronically toxic effects of absinthe.
The leaves are only moderately distinctive. The upper side is a slightly glossy mid-green with a hint of the suggested (by the standard sources) yellowish green, while the lower side is definitely a distinctly paler but fairly uniform slightly yellowish green. The upper and lower ranks of leaves are very flattened, the upper ones having quite obvious translucent spots half way or more up the leaves. The lateral ranks of leaves are, by contrast, strongly keeled and sharply folded in half over the side of the shoots, with tips incurved to the shoot.
The green of the young shoots then abruptly changes into the red brown of the older twigs, but still with old red-brown scale leaves remaining. According to the books the bluntly tipped scale-like leaves of the lateral shoots are replaced by sharper, more lanceolate leaves on the leading shoots.
The female cones have 4 - 6 pairs of scales, only 2 inner pairs being fertile. The cones are typical Thuja goblet-shaped cups, but in this species the rounded scales have slightly mucronate tips. The individual seeds were also found, about 6 mm long, with their membranous wings giving an overall oval shape.
Thuja occidentalis has a fair number of cultivars (over 300), and is quite popular in cultivation . One of the most famous cultivars is Thuja occidentalis 'Rheingold', certainly a very familiar name to me. The cultivars seem to thrive, and I imagine there are many more individual specimens of cultivars grown than there are live trees of the original species. Oddly enough the RHS suggests growing 'Rheingold' in moist but well-drained soil, apart from that not being too fussy about the type of soil. They also warn that skin contact may cause irritation. 'Smaragd' is a neat narrow green column that is also very popular, as an accent or in hedging.
The ecology of the tree in the wild seems to be focussed on wet, but perhaps not completely marshy soils, and also poor alkaline or cliff-face soils where competition from other trees is reduced. On the poor dry soils it apparently doesn't "perform" in garden terms, but can persist, hanging on by its fingerprints. Such trees are likely to be include some of the oldest trees in Canada and NE USA. This is also one of the most frost-resistant trees, once having been frost-hardened, being able to withstand liquid N temperatures
References:
Illinois Wild Flowers, http://www.illinoiswildflowers.info/trees/plants/white_cedar.html, accessed 24th October, 2014.
The Gymnosperm database. http://www.conifers.org/cu/Thuja_occidentalis.php, accessed 24th October, 2014.
USDA Forestry Service. http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/thuja/occidentalis.htm, accessed 25th October, 2014.
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