Pinus wallichiana

Pinus strobus, the Weymouth or Eastern White Pine.

There are at least two trees of the Weymouth (aka Eastern White) Pine, Pinus strobus, in Cobtree Manor Park, one between the elephant house and the pond, and one, somewhat healthier, above the wooden ring structure in the next compartment.

The foliage of both trees appeared fairly yellowish and there is very little to be seen on the lower tree, which has really just got a tuft of foliage only at its very top! Yellowish foliage in Pinus strobus may be an effect of winter weather.

The history of this tree is really quite remarkable. It was first discovered by Europeans in Eastern Canada and the Northeastern USA in the 1500s and 1600s. Before then of course it was well known to the original Americans. The Eastern White Pine was known as the Tree of Peace by the Iroquoi confederacy, the famous Five Nations. The bunches of five-needles indicated the coming together of these tribes at the time of The Great Law of Peace to form the united and dominant force in the region prior to the arrival of the Europeans. The tree was eventually introduced to Europe in 1620 by George Weymouth, apparently being planted at Longleat. The white pines as a whole, and the Eastern White Pine in particular, were the overwhelmingly most valuable timber trees in the United States since the founding of the country. Before the American Revolution the British reserved all large white pine trees suitable for masts for exclusive use by the Royal Navy. In 1919, shortly after Blister Rust was discovered on native American white pines, the value of standing white pine timber was estimated to be over 1 billion dollars!

White pine blister rust, Cronartium ribicola, was introduced into the US from about 1910, on Eastern White Pines imported from Europe to help restore the devastated deforested areas, a fairly ironic step in retrospect!

Once White Pine Blister Rust was identified as such a severe threat, stupendous efforts were made to combat it. As Ribes is the alternate host for the rust, cultivated currants were virtually eliminated in gardens under horticultural control. In one year during the New Deal over 11,000 men were employed to try to remove all wild currant material from US forests. The first phyto-sanitary quarantine laws were introduced to control the spreads of Blister Rust. All this was completely ineffectual, possibly partly because of alternate natural hosts.

Pinus muricata, the Bishop Pine

Pinus muricata, D. Don, 1836

The tree at Cobtree Manor Park appears to have almost collapsed - perhaps being originally on a very short bole (about a metre in this tree) as described in the Collins book. The long needles and chunky cones suggested the possibility of a fire-adapted American Pine, and the sharp spines on the cone scales pushed it towards Pinus muricata,and because of the dark green rather than the somewhat blueish foliage of var. borealis, this is perhaps likely to be var. muricata.

The species is very restricted in its native habitat, and it is confined to a few (only 7 !) cliff-tops and islands. In addition, var. muricata is only found in the 5 southern-most stands, while var. borealis is found in the Northern 2 stands. Despite repeated attempts, no hybrids between the two varieties have been produced to date. The name Bishop Pine seems likely to have come from its original first known location, near the Mission at San Luis Obispo. It has also been called the Obispo Pine, the Prickle Cone Pine, the Santa Cruz Pine, and the Dwarf Marine Pine.

The bark could well be said to be blackish, although I would have perhaps preferred the description very dark grey. The buds did look somewhat reddish, definitely with appressed scales, and I would have said the intensity of their colour had been quite noticeably dulled with white resin (pictured above), making them a rather lifeless pinky-brown to the eye, about 3 cm long. The leaves were all in pairs, stiff and curled, quite fitting the Collins description. Here is a picture taken in October 2014 of a shoot with what I think must be developing female cones at the tip:

Mitchell states: "All leaf surfaces with stomatal lines, margins strongly serrulate, apex abruptly conic-acute; sheath to 1.5 cm, base persistent"

The cones were suitably large, certainly nearer 10 than 5 cm. The prickles on the cones are said in Collins to be small, but I would have said they were rather noticeable! None of the cones seemed to be open, but I should check that next time!

The Bishop Pine can be found in some large gardens, and has also been trialled in a few plantations (according to dyplant on ispot, there could be a plantation close to New Road, West Blean Wood). It seems to do better in the damper and milder SW, and it has been successfully planted on a reasonable scale at Wareham, Dorset. Experience appears to indicate it needs a lot of formative pruning to develop any decent straight wood. From its origins, it is likely to be very tolerant of coastal conditions, and wind-speed, and can reputedly grow at up to 2.5 m. a year.


References:

Calflora. Pinus muricata. http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=6520. Accessed 25.10.2014.

The Gymnosperm database. Pinus muricata. http://www.conifers.org/pi/Pinus_muricata.php. Accessed 26.10.2014.

Thuja occidentalis, the Northern White Cedar

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.