North Island large-leafed kōwhai is the tallest of eight species of sophora endemic to New Zealand, although the genus is found throughout Asia, America, Europe and the Pacific. It belongs to the pea family, which includes gorse, broom and the native kākābeak. Growing to 12 metres, Sophora tetraptera is suitable for a street or garden tree if carefully staked when young, and is great for attracting tui, bellbirds and kākā. Two features make the kōwhai unusual among our native plants: first it is semi-deciduous, and secondly, unlike most New Zealand plants whose blooms are white and inconspicuous, its flowers are a striking sunny yellow. (In te reo Māori the word for yellow is kōwhai) The springtime blooms on the barren branches of the kōwhai are a sign for Māori to plant kūmara and gather kina.
The tree was also used for medicinal purposes: bark collected from the sunny side of the trunk was steeped in water to make wai kōwhai, which was used to treat pain, wounds, skin diseases, and constipation. It is said that in 1925 when the ‘Invincibles’ All Black, George Nepia sustained a severe leg injury and was threatened with surgery to avoid blood-poisoning, he instead chose the kōwhai cure. Two weeks after bathing in wai kōwhai he captained Hawkes Bay to victory over Taranaki. All parts of the tree contain a toxic alkaloid called cytisine, or sophorine, which seems to help people stop smoking, but is also a powerful purgative. After a group of whalers stole the grog of an old Bluff brewer he got revenge next time they were in port by putting boiled kōwhai leaves in his brew. "For 12 hours straight they were erupting at both ends." (Vennell, The Meaning of Trees)
This particular tree is on the Meadow Walk.
Maples from Around the World 1
Over the last five years Cambridge Tree Trust has been planting a maple arboretum, which now has approximately 35 different species of maple from North America, Europe, and Asia. The area is accessed from Thornton Road and there is a gravelled walking path. Take a stroll in spring as the lovely new leaves unfold, or in late autumn to admire the gorgeous leaf colours.
From North America we have big, handsome trees, often displaying brilliant autumn colour. These include, from the Eastern states, the sugar maple (Acer Saccharum) which of course gives us maple syrup, the red maple (A. rubrum), and the silver maple (A. saccharinum) so-called because of the soft lustre on the back of its leaves. There is also the lovely snake-bark maple (A. pensylvanicum) known as moosewood, a smaller tree and therefore at the mercy of browsing moose. From the Midwest we have the Manitoba maple (A. negundo violaceum), remarkable for its delicate pink flowers in spring (shown). Finally from the Northwestern states we have recently planted the big-leafed Oregon maple (A. macrophyllum).
Europe has fewer species of maple, but they tend to be very hardy types. In the arboretum we have the tall Norway maple (A. platanoides), and the more moderate-sized Caucasian maple (A. cappadocicum), both suitable for street planting, and also the humble field maple (A. campestre) which is used in Europe to form hedges.
Finally we have a large number of elegant Asian species, which tend to be smaller, and in Japan are a cornerstone of garden design. But these will be discussed in next month’s article.
In the depths of winter the velvety brown buds of the Michelia open to reveal an amazing display of large, heavily-scented, creamy-white blooms. To some the fragrance is exquisite, to others it is almost overpoweringly sickly. An evergreen tree, the Michelia can grow to 20 or 30 metres in height, although garden centres have smaller varieties such as ‘Silver Cloud’, which reach to only half this height. It is very popular as an ornamental feature in parks and gardens, is sometimes used as a street tree, and can even be pruned as a hedge.
Michelia doltsopa is a native of the Eastern Himalayan region and of the Meghalayan subtropical forests of North Eastern India. It is a member of the magnolia genus, and as such is also related to the liriodendron (tulip tree) of the Eastern USA, which is the giant of the genus, growing to 60 metres or more. The wood of the Michelia is a rich brown colour, and like the flowers is very fragrant. In Nepal and Bhutan it is used in house-building, where in recent decades it has sometimes suffered from over-harvesting
This tree is is Cambridge Road.
Japanese Persimmon (Diospyros kaki)
An excellent medium-sized specimen tree for a small, sheltered garden, the persimmon has glossy tropical-looking leaves which turn orange to burgundy in autumn, and delicious orange fruit which holds into winter, providing food for birds (waxeyes) and humans. Try them baked with honey and star anise, as a sorbet, or eat them fresh: the non-astringent varieties can be eaten when crisp like apples or used in salads, but the astringent ones which are high in tannins must be left to ripen to a jelly-like consistency and spooned out. In Asia the persimmon leaf is often dried to make tea, Kaki-No-Ha-Cha. In Japan the fruit is dried to make Hoshigaki, a ‘fudgy, fragrant’ sweetmeat like a ‘date crossed with an apricot’, while in Korea dried persimmon is used to make a spicy punch, or the fruit fermented to make a vinegar. Usefully, dried persimmon is also said to scare away tigers.
The Japanese persimmon was introduced to California and southern Europe in the 1800s and to Brazil in the 1890s. Its Latin name Diospyros is popularly thought to mean ‘pear of the gods’. There is also a North American form of the tree: indeed the word ‘persimmon’ comes from the Powhatan language of the Eastern USA, and means ‘dry fruit’, referencing its astringent nature.
The persimmon belongs to the same genus as ebony but its wood, although hard, cracks easily. In Asia it is used for furniture panelling whereas whereas the American form is used for making billiard cues, weaving shuttles, drum sticks and high quality heads for golf clubs.
This is an elegant and graceful shade tree, which deserves to be in much greater use as a street and garden tree. Its natural umbrella shape and soft foliage provide a cooling canopy of dappled shade. It is drought and frost tolerant, grows only to about eight metres high, and although it is deciduous the leaves are soft and create little mess. Besides, it is late coming into leaf and looses its leaves early in autumn. It is very decorative in January and February when it is covered in masses of pink powder-puff flowers, providing nectar for birds and bees. The flowers are very small, occurring in bundles, with the stamens much longer and more showy than the petals. These then give way to small, flat seed pods. So instead of buying a shade umbrella for the back garden, plant a silk tree and prune off the lower branches to give you summer shade, cooling transpiration and beauty.
The silk tree is a member of a genus of about 150 tropical and subtropical trees which are found in Australia, Asia, Africa and the Americas. It is named after Filippo degli Albizzi, the Italian who first introduced it from Persia (Iran) to Europe in the mid-eighteenth century. Besides their ornamental value, some species of Albizzia are used for timber, for their antibacterial properties, and in semi-arid regions as a forage crop.
Also known as the fern tree, the graceful and spectacular jacaranda is a native of Bolivia, Argentina and Brazil, and one of their most beautiful exports. In Sydney, Perth, Pretoria, Lisbon, and in Pakistan and the Caribbean jacarandas lift the spirits; planted with gay abandon they create an amethyst canopy of fragrant flowers over suburban streets, and lay a purple carpet beneath, while the delicate emergent foliage castes a welcome summer shade. A great investment as a street tree not only for their beauty but also their contribution to air cleaning, urban cooling, and community mental health.
Jacaranda is a member of the bignonia family, which includes catalpa and paulonia. Grown in well-drained soil in full sun and frost free, it can reach 20 metres in height. It is deciduous, and may bloom twice a year. Despite the beauty of its flowers all parts of the tree are poisonous, ‘causing vomiting, diarrhoea, irregular heart beat, dilated pupils, coma and death’. The pale wood, when still green, is used for turnery and bowl making. Extracts of jacaranda also have antimicrobial properties against E. coli and Staphylococcus aureus.
In folklore the jacaranda is associated with wisdom, rebirth, wealth and good luck. If its flower falls on your head it is thought to bring good fortune. In Queensland late spring is known as the ‘Purple panic’, the time when the jacaranda flowers and students are stressed out completing assignments and preparing for final exams. However in Pretoria it is said that if the flowers fall on your head it means you will pass your exams!