September in the Garden 2024

Nothofagus antarctica

This month, I present a number of unusual deciduous trees from the Botanical Garden’s collections. Mostly horticulturally-obscure and little-mentioned, they are, once pointed out, at times significant elements in the Garden.

One of the first trees people notice from the boardwalk at the Garden entrance is the giant Tapiscia sinensis next to the Campbell Building. The common name “Chinese false pistache” comes from the scientific name: Tapiscia is an anagram of Pistacia, the genus of the pistachio, to which there is a passing resemblance. This magnificent example may be the only one of its kind in North America, and even well-traveled botanists are usually stumped by it. Flanking it are two unusual trees. Toward the building is a fine sapling of Gymnocladus chinensis (Chinese soap tree), and on the other side (to the west), the luxuriously-needled Pseudolarix amabilis (golden larch). The Gymnocladus has a somewhat more familiar North American relative—Gymnocladus dioicus, the Kentucky coffee tree—which can be seen in the Carolinian Forest Garden (in the Rafinesque and Bannister Groves), but the Chinese species is arguably the more elegant in leaf. The pattern it creates is lovely and readily studied, as the branches have not yet surmounted the boardwalk railing. Both species have sizable legumes with saponin-rich pulp (saponins are toxic compounds known for their ability to produce suds, which is the derivation of the name, Chinese soap tree). The golden larch is a deciduous conifer. Though ours is quickly gaining height, it has not yet matured to the cone-bearing stage (the cones look like little globe artichokes). It is a stunning example of an attractive species, nevertheless.

On the other side of the boardwalk—that is, facing northeast—opposite the Campbell Building are several interesting and unusual deciduous trees, including Lagerstroemia subcostata var. fauriei (Yakushima crepe myrtle), a tree with beautiful peeling bark from the Japanese island of Yakushima. Whereas most locally-cultivated crepe myrtles are hybrids with the florally-spectacular Indian crepe myrtle as a parent and were devastated by this January’s sudden freeze, this species was unaffected. Its flowers, which may still be visible in September, are white and rather less impressive than those of its tenderer kin, but few trees can compete for bark effect.

The David C. Lam Asian Garden, our largest garden area, holds the greatest number of uncommon and unusual species. Many are broadleaf- and needleleaf-evergreens, but I’ll stick to the program as I promised deciduous ones. On the immediate right, entering the Asian Garden on Upper Asian Way is a substantial example of Diospyros lotus (lotus plum). Some visitors and readers might be familiar with the Asian persimmon, Diospyros kaki, with its extraordinary, autumn-borne orange-sized orange fruits (there is a small tree in the Food Garden). Like the persimmon, this species usually has glossy leaves, but its fruits are fingernail-sized and blackish, and commonly dried and eaten as snack food. All parts of the plant—flowers, fruits, leaves and wood—have an odd smell that is especially noticeable on humid days. Note that there is also a group of young lotus plums west of the Main Lawn close to the Service Yard hedge.

Meliosma alba is a stand-out in many ways. Not only are the meliosmas rare in cultivation, they belong to an otherwise tropical family (they are the only members of the Sabia family even remotely cold hardy). This particular species also has one of the oddest geographical distributions of any plant in the UBC collection, in that it is native to both southwestern China and Mexico. Along with this unusual “disjunctive” distribution, the species is also known for its “explosive” pollen. When ripe, the tiny flower buds open abruptly, and the pollen explodes outward. Meliosmas are often called bubble trees because of the audible sound of the opening flowers (likened to champagne bubbles). Looking up from Decaisne Trail across Rock Creek, M. alba shows its light-coloured leaflet backs, though it’s the whitish flowers which give the species its name. Less extraordinary, but still pretty unusual, is Hovenia dulcis, the Japanese raisin tree (on the island in the middle of Wharton Glade). You might think that it’s the fruits of this tree that are raisin-like, but you’d be wrong. The fruit is actually a hard nut. It’s the stem on which the fruit is borne that becomes fleshy and wrinkled. Edible and sweet, across East Asia, these stalks are traditionally eaten as trail-side snacks or made into alcoholic drinks. If you look up into the crown, you may be able to see the developing nuts.

An unusual tree with no particular human use is Tetracentron sinense (spur leaf). It is a fascinating species, nevertheless, and it is native across southwest China, northern Vietnam, and the eastern Himalayas. Several specimens are in close proximity near Lower Asian Way between Flanagan Trail and Wilson Glade. Look for the hanging, catkin-like fruit clusters, especially on the individual close to Lower Asian Way next to (the presently decommissioned) Forrest Trail. Note that the tiny dry fruits are produced in multiple whorls of four all along the stalk. Although essentially hidden by their small size, each bears a persistent spur-like stigma (the pollen receptive surface of the female part of the flower). This is the derivation of the genus name (tetra = four + kentron = a spur). The common name “spur leaf” refers to a completely different kind of spur; that is, the stub-like “short shoots” on which the leaves are borne on the older stems. Tetracentron has only one close relative: Trochodendron aralioides (wheel tree), a broadleaf evergreen (sorry!), and admittedly, an unlikely-looking relation. There are several in this area and elsewhere in the Asian garden that can be compared with Tetracentron.

A specimen of the Japanese Euptelea polyandra sits near the corner of Lower Asian Way and David Trail. This unassuming Japanese tree, which belongs in its own family, produces exceptionally coarsely-toothed leaves, and earlier, in the spring, strange petal-less flowers with long, dangling red anthers (the pollen bearing parts of a flower). There are two species in Euptelea—the other is in China. Both rate the “unusual” label, as they are definitely uncommon, but also Tertiary relicts (survivors from plant communities that were widely distributed across the Northern Hemisphere during much of the Tertiary Period (i.e., 65-15 million years ago)).

Two of the tallest deciduous trees in the collection might be Liriodendron chinense (Chinese tulip poplar) and Bretschneidera sinensis. Our largest Bretschneidera (on Sargent Trail, and best viewed from the Tree Walk) is a fascinating specimen. Planted in 1996 and currently around 18 m tall, and with no sign of slowing down, this exceptionally rare tree had, for its first fifteen years, no side branches and only a radiating cluster of super-sized leaves atop a ramrod-straight stem. Happily, it finally grew out of the beanpole stage and had branches, but we now patiently wait for it to begin flowering. At some point in the future, white or pink foxglove-like flowers will be borne in impressively large clusters at the top of the tree. Watch that space. Our Chinese tulip poplars, also notably tall, are much like the more commonly-grown American Liriodendron tulipifera. Both species have broad, four-lobed leaves, unlike any other temperate tree. The lobes are slightly more pronounced on the Chinese species, but otherwise, the two look pretty much alike. Check out the lower side of Soulie Loop for the Garden’s most accessible and visible specimen, then look up. There are several fine, accessible examples of Liriodendron tulipifera in the Carolinian Forest Garden. In this neighbourhood (i.e., in a number of Carolinian beds) is Asimina triloba (pawpaw), an unusual eastern North American colony-forming tree. Like Diospyros and Meliosma, Asimina is a cold-hardy outlier in an essentially tropical family. Its flowers are malodorous brownish-purple bells, but its yellow fruits are fleshy and elongated (intermediate between a plum and a banana) and edible, which is why you can find the plants (sadly fruitless, so far) in the Food Garden.

Finally, Nothofagus antarctica (Antarctic beech), which is native to southern Chile, can be found at the highest point of the E. H. Lohbrunner Alpine Garden in the South American Section. In fact, it is probably the only one. In spring, the new leaves of Antarctic beech smell of sandalwood soap. It is one of the few deciduous trees from the Southern Hemisphere that we grow. In Tierra del Fuego, the species can be found as far south as 56° S latitude, making it the southernmost tree in the world.