Sunday, May 8, 2011
Evil Invaders of Vancouver Island
Spring seems to have finally come to Edmonton, or at least all the augers seem to say so: the marsh marigolds leaves popped up along with the first crocus blooms (‘Ruby Giant’ Crocus tommasinianus Herbert on 24 April), the rhubarb punched its way through the snow (26 April), the first bumblebee queen was sighted (29 April), sandhill cranes gruked their way overhead (2 May), the first chionodoxa bloomed (May 3), the last of the snow went (4 May), the coltsfoot flowers opened (4 May), the first tulip bloomed (5 May), and the first Andrena bee descended on the coltsfoot (6 May). Even the first migratory songbird, a Swainson’s Thrush, made its appearance at the bubbler in the back (6 May). And surest sign of all, I’m puttering around in the garden again.
Although the winter was long and harsh, the unusually heavy snow pack gave me some hope that winter mortality would be less than usual. Alas, there is no sign of that and it looks like I may have several open spots to fill where exotic ‘perennials’ have become dead organic matter. One pleasant surprise, however, was the reappearance of one of last year’s experiments – a leafy vegetable that is a perennial in warmer climates, the Turkish Rocket (Bunias orientalis L.), also know by the degustibusnondiputandulatory name Turkish Warty Cabbage. Only one seed in the packet germinated last summer, and the resulting rosette looked sad and shaded under the overgrowing tomato (although this may have allowed it to hide in plain sight from the introduced cabbage white butterflies whose caterpillars ravaged all my other Brassicaceae). The young leaves are very peppery and, other than the coltsfoot stalks (which you can boil like asparagus – but in the HBG, these are for the bees), the only edible item in the Home Bug Garden at this time of year.
Unfortunately, Turkish Warty Cabbage seems to be pretty vigorous and has naturalized (or become a weed, if you prefer) in British Columbia and much of north eastern North America, so it will bear watching. If seedlings start showing up, I may have to have a feast instead of a nibble. Predicting the potential of a plant or animal from an exotic locality to become established in a new land is one of those mysteries that Science seems to have made little progress in unraveling. Some do and some don’t, but those that do and spread rapidly typically have propagules with high vagility, e.g. tasty berries that birds love, fluffy seeds that disperse on the wind, or wings which do the same as fluff for animals. The seeds of Turkish Warty Cabbage are large and lumpy, so I doubt they move far on their own. In contrast, the European Paper Wasp Polistes dominula (Christ, 1791), is far too vagile, appears to be spreading in many parts of North America, and was the most obvious insect in late April gardens on Vancouver Island (bumblebees being second).
Mrs HBG and I took advantage of the late Easter break to visit the mother-in-law on Vancouver Island on the coast of British Columbia. We lucked out with two days of mostly sun to one of rain, so most of the time was spent walking through coastal rainforest or visiting gardens (vs watching slugs), but we devoted one morning to the impressive Royal British Columbia Museum in Victoria.
The RBCM has many interesting displays, but the one devoted to invasive species seems more thoughtful than most of its kind. I’m still ambivalent about the false native vs alien dichotomy that I think has poisoned the study of spreading species, but I can largely agree with the first paragraph on this RBCM plaque.
I don’t like several of the implications of the second paragraph – primarily the removal of ‘humans’ from nature and the use of the emotive ‘alien’ – but at least the aboriginal inhabitants of Vancouver Island are inferred to have been capable of introducing species they liked to the Island.
As a practical definition, though, I think the first sentence of paragraph II is okay (using a neutral term such as ‘introduced’), but it is really the introduced species that are able to spread into ‘natural’ habitats that are the problem and these are not the bulk of the species that have been introduced to Vancouver Island over the last 160 years. A good example of this is Butchart Gardens in Victoria – almost entirely given over to ‘alien’ plants, most of which have not moved into the forests and meadows that pre-existed European settlement.
Here’s a final example for consideration, and one that led to some wry feelings in the HBGardener. As we were leaving Butchart Gardens after many hours of wallowing in alien flowers, we noticed something scampering across a rock wall. To our amazement, it was a beautiful lizard! Lizards are as common as birds in Queensland, but Alberta has none but a horny toad (Phrynosoma douglassii brevirostre) that barely manages to scuttle into the southeastern corner of the Province. We were delighted, but at a loss as to the lizard’s identity. Much to our chagrin, the next day at the RBCM we learned that it was the European Wall Lizard (Podarcis muralis Laurenti, 1768): a dozen lizards were released into the wild when a small zoo on the island shut down and now they are scampering around much of Victoria. We were crest-fallen: what we thought was a delightful animal was an evil alien invader.