Betula bark

Betula bark

Betula bark

BARK AND TRUNKS

A great way to enjoy the Mt Lofty Botanic Garden in Winter

 During the Winter season different aspects of the trees with which we are so familiar become apparent.  This walk is designed to introduce you to a few of these features.  As you entered the car park you may have noticed a tall conifer on your right, Sequoia sempervirens, Californian Redwood, a member of the Taxodiaceae family.   The dark red-brown bark is very fibrous with deep clefts, and can be up to 30cm. thick, with a very high tannin content, which protects the tree from insects.  One of the tallest trees in the world, and now protected in many State parks in the US, they were exploited by early European settlers for house-building because the timber was so durable.

 Leaving the carpark, walk back along the entrance road and take the left hand fork down to the lower section of the carpark.  On the right hand side a group of Acacia melanoxylon, Tasmanian Blackwood, has dark rough-textured bark.  The wood has been used for furniture, and as it bends easily when steamed was popular for coaches, boats and barrels.  Aboriginal people used it for shields and spear-throwers, and the inner bark for string.  Medicinally an infusion of the bark was used for rheumatic joints.  Continue walking down through the car park until you arrive at a small ramp down into the arboretum.  Throughout this area there are many Betula or Birches, the only trees native to Iceland and Greenland.  Among the 30-35 species found throughout the northern hemisphere we have here –

o  B. traveculosa – flaking bark above head height

o  B. forrestii – deeply lobed bark

o  B. x coerulea – lichens contrasting with smooth, white bark

o  B. kirghisorum – from the USSR

o  B. tortuosa – from the Arctic

o  B. pendula – yields a pain killing drug, oil used for skin afflictions

o  B. nigra – called black birch after the very dark colour of its lower bark, while the upper parts are silvery grey.  This is the best of birches for damp places.

 Continuing on to the bitumen path you will find several Populus ciliata, recognizable by the “arrow-head” shapes on the trunk where branches have fallen.  The wood of these trees has no smell or taste, and was popular for food containers and implements before the introduction of plastic.  It is slow to burn and therefore used for matches.  Nearby a Salix koreansis or Korean Willow has attractive wavy ridges on its bark.  Until World War I, the bark of Salix alba was the main source of salicin used in the production of aspirin.  Willow wood has long been used for manufacture of cricket bats, and the tree makes good charcoal.  Also on the right hand side of the path a Diospyros virginiana, Common Persimmon, has many small fruit and tessellated bark. 

 Next we find on both sides of the path Pterocarya tonkinensis, Tonkin Wingnut, from Vietnam and China.  There are many lichens on these trees, and interesting scars where the branches have fallen off.  A grove of Alnus incana, Speckled Alder, near the flax plants reminds us that their massive roots help to protect river banks from erosion.  Piles made from Alder wood were used to support the buildings in Venice, and Dutch clogs are also made from this timber.

 Bischofia javanica, Toog, line the path uphill beside the dam spillway.  Toog is one of the most important timber trees of Indonesia and S-E Asia, and Samoans process the bark to extract a brown dye used in colouring their patterned tapa (siapo in Samoan) cloths.  Continue on the path uphill towards the road through a grove of Celtis bungeana, Bunge’s Hackberry, previously a member of the Ulmaceae family, but unlike the Elms these trees do not bear winged seeds.  They are now included in the hemp family, Cannabaceae.  Valued for their drought tolerance, in Chinese medicine the bark is recognised as effective in removing cough and dispelling phlegm.

 Walk along the road towards the Duck Pond, where on the right a stand of Quercus palustris, Pin Oaks, will be bare, but their drooping branches will be very evident.  The American Indians valued this feature of the trees as the snow would hold on the branches forming tunnels through which they could walk.  The timber is light brown, hard and strong and used for shingles.   

Down the bank on the left hand side several Taxodium distichum, Swamp Cypress, one of the very few deciduous cypresses, are dropping their rust coloured leaves.  This tree can tolerate extremely wet conditions, growing in a metre or more of water in the Everglades of southern America.   The ground around the trunk bears many “knees” which are thought to assist with respiration and also help to stabilize the trees.  The fibrous bark is reddish-brown in colour, and the wood is extremely hard and sought after in the US for building.   Just behind you can see another, Taxodium mucronatum, Mexican Cypress or Montezuma Cypress that has very different foliage showing good colour, and a clean trunk.   This one is evergreen or semi-evergreen growing into a tree with a very stout trunk.  It does not produce the “knees” seen in the Swamp Cypress.

 Just past the Duck Pond you can walk down the bank to a Quercus suber, Cork Oak, and examine the thick corky bark which is harvested in Spain and Portugal to produce corks for wine bottles and other uses.  Nearby several Catalpa bignoides, Indian Bean Tree, easily recognised by their crop of long beans, have fine striations on the bark.  Closer to the lake a beautiful Sequoidendron giganteum is a relative of the first tree we looked at, though more heavily built.  These trees contain the largest timber by volume of any tree and are very long-lived.  The bark is rough, deeply fissured, and reddish-brown.  On your right you cannot miss the beautiful red, silky bark of Araucaria beccari now known as Araucaria hunsteinii, Klink’s Pine, the tallest tree in New Guinea.  Beside the road the rough red bark and pendulous needles on Pinus patula, Mexican Weeping Pine, also cannot be left off our list. 

 Continuing along the road on the left Calocedrus decurrens, Incense Cedar, has deep fissures in the bark.  Nearby the Pseudotsuga menziesii, Douglas Fir, is a fine specimen of one of the best timber trees on earth.  The American Indians believed that the three-lobed scales protruding from the attractive cones were the hind legs and tails of little mice sheltering within.  Around the corner Pinus strobus is another timber with no perfume, making it a useful softwood.  The trunk is 2-toned, and rings can be seen around the trunk where the branches have fallen off.  The bark remains smooth.  The last on our list is a Pinus radiata, a remnant from the pioneer plantation before the establishment of the Mt Lofty Botanic Garden.

This walk has been prepared by volunteer Garden Guides who are members of the Friends of the Botanic Gardens of Adelaide