February in the Garden 2026

Acer pentaphyllum (five-finger maple)

As mentioned in last month’s blog, conservation of plants normally encompasses two broad categories: ex-situ and in-situ conservation. In-situ conservation (also known as habitat preservation) is normally the purview of governments, such as with parks and protected areas. There are even a few botanical gardens fortunate to have their own wild lands, or that have the resources to facilitate the protection and management of wild habitats. Sadly, UBC Botanical Garden has neither the land nor resources to accomplish either, so we embrace a slightly more arms-length approach to in-situ conservation that includes education about and advocacy for threatened habitats. Our Garry Oak Meadow Garden, for example, features plants from a local, endangered ecosystem, and this gives us a platform from which we can inform visitors not only about this important community, but also about biodiversity and conservation in general. If you haven’t seen the interpretive signage there, please have a look.

On the other hand, ex-situ conservation is a means to physically preserve genetic resources. In practice it is sometimes known as the conservation of last resort, because it is often employed when habitat preservation is seen as inadequate insurance against extinction in the wild. This is the case with the two Asian maple species mentioned previously: Acer pentaphyllum (five-finger maple) and Acer amamiense (Amami maple).

In 2010, UBCBG took part in a botanical expedition to the Hengduan Mountains of Sichuan Province in China to observe and collect wild Acer pentaphyllum. Andy Hill, curator of the David C. Lam Asian Garden, was part of the multi-institutional team that assessed the remaining populations and collected seed and material for genetic fingerprinting. This maple was targeted for ex-situ collecting because remaining wild populations were (and still are) in danger of being completely wiped out by flooding from a series of proposed dams downstream. Further, the genetic diversity represented in the species was already diminished because of declining numbers due to habitat loss. In a situation like this—a “genetic bottleneck”—there is a declining probability that offspring from a shrinking population will display the range of variability once exhibited when the species was more numerous and inhabited a larger area. There is a danger that traits that confer cold hardiness, drought- or heat-tolerance, or resistance to a particular disease could already be lost to the species. It was therefore deemed critically important to collect seeds from as many individuals and populations as possible, and also to plant them out in a variety of ex-situ environments.

In 2024, Ryo Sugiyama, curator at Nitobe Memorial Garden, and I were part of an expedition to the island of Amami in southern Japan. There we visited the only known population of Acer amamiense, which had been dubbed “the most endangered maple in the world.” We observed and recorded flowering specimens and seedlings. Prior to our visit, little was documented about the habitat or population size, or its health and reproductive potential. What we found was a tiny, but seemingly thriving population. There were hundreds of seedlings but only a handful of mature trees, and just three that could produce seeds (the species has separate male and female individuals). A relief, but also gravely concerning. The population is not only small, but its sole habitat is less than one hectare in size and precariously perched on a steep hillside less than 30 m above the ocean, in a tsunami zone. Our Japanese partner revisited the site later that year to gather material for DNA analysis and collect seed, which was then provided to us and our partner at Westonbirt (England’s National Arboretum) in Gloucestershire. Seedlings from these collections at UBC BG are now ready to be planted out, once our new “Amami Maple Grove” is ready. Because of several generous donations, this area, beyond the Greenheart Tree Walk in the Asian Garden, will be ready with new trails and areas for planting early this spring.

At UBC, more than 100 Acer pentaphyllum trees, representing twelve different seed collections, were initially planted out in the Asian Garden, the greatest number located in the “Pentaphyllum Grove” at the far end of the garden. After 15 years, there are about 20 surviving specimens. We didn’t expect all or even most of the seedlings to survive the vagaries of Vancouver’s climate, but the survivors are expressing superior cold-hardiness and summer drought tolerance, and probably represent a genetic expression not represented by collections elsewhere. Currently, we have 34 Acer amamiense seedlings ready for planting, and another hundred or so seed ready to be sown at the Botanical Garden Nursery. Our expectations for the Amami maples are similar to that for the five fingered maple, but there is hope for even greater success.

As we’ve seen in Sichuan and on Amami Island, maple populations are often isolated and sometimes exceptionally small. This is a particular concern in temperate mountain habitats, where habitat loss due to development and climate change sometimes goes unchecked. The unfortunate result is that one in five maple species worldwide is now threatened with extinction. It may be too late for the soon-to-be-flooded habitat of Acer pentaphyllum, but worth considering that on Amami Island, one typhoon, earthquake or tsunami could potentially take out the mountainside that is home to the entire wild population of A. amamiense. Maples are familiar trees—especially so in Canada—but because they are common across much of the developed North, we might just be taking them for granted. We can’t let familiarity make us complacent about the survival of species in more vulnerable parts of the world. Through the Global Conservation Consortium for Acer, for which UBC Botanical Garden is the lead institution, we are working to mobilize individuals, sister institutions, agencies and governments to help us prevent their extinction.