The new year brings with it the promise of increasing daylight. My favourite formal greeting at this time of year is an ancient Latin salutation, Sol Invictus (the invincible Sun), which celebrates that very certainty. January also brings, statistically speaking, our coldest weather. It’s not surprising that gardeners are often nervous about a potential deep freeze at this time of year. In general, however, the worst damage to plants by cold temperatures nearly always occurs in November or March, when plants are not so safely in a state of dormancy as they are now.
Exactly a decade ago, I introduced my January blog this way. Plenty of weather has flowed under the bridge since then, and I feel I should amend my opinion of the worst months for cold damage to include January. Readers might recall the January two years ago, which followed a relatively mild and nearly frost-free December (much like the one just past). The blow came suddenly on 11th of January, 2024 with temperatures falling 17 degrees C over 24 hours and bottoming out at minus 13 C at YVR (it was even colder at the Botanical Garden). The cold was accompanied by particularly fierce winds from the east, and this created a serious windchill effect. Damage was extraordinary and widespread, affecting to the greatest degree those plants from warm temperate climates whose cold-dormancy requirements had already been met, and whose buds were already starting to swell, indicating that sap was starting to move.
Which brings me to the subject of today’s blog, which concerns conservation. Surveying the damage from the winter of 2023-24, or indeed, from the devastating heat-dome of June 2021, shows us that damage from those extreme events, though profound, was actually rather uneven in the Garden. As one might expect, plants of the same species were affected differently, depending on where they were situated; clearly, in this case, protected environments were beneficial. However, it also appeared that seedlings, growing together under essentially the same environmental conditions, were affected differently, one to the next. This should not be surprising, as each seedling plant is a genetically unique individual, and variability is nature’s way of ensuring that any one disastrous weather event, disease or pest infestation doesn’t wipe out all individuals in a population.
This is why we tend to grow multiple seedlings of the species we consider for our scientific collections, and why this approach is doubly important for our ex-situ conservation collections. Ex-situ conservation refers to collections that are assembled “away from the (native) site.” Seed banking is a common and perhaps more familiar method of ex-situ conservation, but documented living collections of plants can also be effective.
There are generally two goals in ex-situ conservation. As with habitat (i.e., “in-situ”) conservation, the first and over-riding goal is to prevent a species from going extinct. In the best-case scenario, the entirety of a species’ genome is included in what’s being saved, so that a collection of seeds or plants might have in its genetic makeup sufficient variation to survive the rigours of current and future environmental disturbance. Such a collection will allow a species to have a better chance of surviving repatriation, which is typically the second goal. A related, often more realistic goal, is to facilitate the widest distribution of plants possible, because it’s never a good idea to have all of one’s eggs (or seeds, or plants) in one basket. Climate change might render a native habitat inappropriate for repatriation, a disaster might cause a seed bank to fail or a wildfire might burn down a garden. This is why these initiatives are often multi-institutional efforts: we increase the probability of success by spreading the risk.
Effective ex-situ conservation in the Garden thus requires significant numbers of seedling plants from across the species’ geographical, edaphic (soil-related) and elevational range. This is no easy task, either in collecting or having the space to grow the seedlings out. It becomes simpler and less problematic where populations are already reduced, such as with the Botanical Garden’s two important ex-situ collections: Acer amamiense (Amami maple) and Acer pentaphyllum (five-fingered maple). I will follow up in February by describing these two efforts.
Written by:
Douglas Justice
Associate Director, Horticulture and Collections
UBC Botanical Garden
