Like most of its relatives, the Pink Wintergreen has unusual stamens that release pollen only from a pore at the tip (tomatoes and their relatives also have this type of stamen). Only certain bees are able to collect pollen from these flowers through a technique called buzz pollination. Essentially, a bee grabs hold of a stamen and shakes the pollen out by vibrating its wings and body. Most of the northern European species of wintergreens (including Pyrola minor, rotundifolia, chlorantha) studied by Knutsen & Olesen (1993 American Journal of Botany 80: 900-913) did not produce nectar and were mainly buzz-pollinated by bumblebees (Bombus spp.). The pistil is located far away from the stamens, so one would assume that outcrossing is preferred by Pink Wintergreen. We have lots of bumblebbees in the Home Bug Garden, and also leaf cutting bees (Megachile spp.) that are good buzz-pollinators, but instead of spending my days watching the pyrola to see what comes to pollinate, I trudge off to work. No accounting for taste.
Wednesday, June 23, 2010
Gardens North is a fine place to find the seeds of many North American wildflowers and other unusual garden plants that are wildflowers in other parts of the World. They have a great on-line catalogue with thumbnails of flowers and information about their diversity of seeds that has helped me through many a long winter’s day. One thing that I especially like is that they point out problems one might have with their seeds. For example, for Pyrola asarifolia, which they stock, they note in their germination instructions: “There is no known method for germinating this species in an artificial setting.”
I’m not sure that I am up to that kind of challenge, but no worries, a P. asarifolia seed or two figured out how to germinate in my yard all by itself. When I moved in I found a half-dozen leaves of Pink Wintergreen (also less euphoniously known as Bog or Liverleaf Wintergreen) peaking out from under the ground-hugging limbs of a giant white spruce, the trunk of which forms the southwest corner of a neighbour’s front yard, and the boughs of which formed a quite adequate barrier to block dogs from running across my yard. Other than mulching around the wintergreen and weeding out competing grass and dandelions, nothing much happened for several years until the neighbour decided to do some timber stand improvement and limbed the tree to 2m. Suddenly, dogs started crashing across the yard and previously invisible people strolling on the street seemed to always be staring in our front window whenever I had an inconvenient itch or trod through the living room in less than formal attire. A fence, a raised bed, numerous new plants, and a couple of years of labour later that corner of the yard is at least dog resistant. One beneficiary of the increased attention to that part of the yard has been the wintergreen. What was once a half dozen marginal-looking leaves is now a spreading groundcover. Even better, attractive spikes of pink flowers began appearing last year and have just started blooming again this year.
It is sometimes said that the highest diversity of plants in temperate forests is the stratum of the herbs and small shrubs near the forest floor (e.g. a pleasant stroll through the understory in the Saskatchewan River Valley see The Garden Ms S). I suppose that it true – the understory of tropical rainforest tends to be boring – all of the action is in the sun-drenched canopies where trees, epiphytes, and lianas express their diversity 50 or more metres above ground. Since light is at very low levels on the forest floor, understory plants often grow very slowly and try to keep their leaves as long as possible, even in very cold climates. Being evergreen is a way to conserve previous investment in growth and take advantage of any light that happens to come along when temperatures are warm enough for photosynthesis.
Another way for forest floor plants to persist in low light levels has recently become a fervid topic of research interest – myco-heterotrophy. The associations between certain fungi that collect mineral nutrients and the roots of plants that exchange excess carbohydrates for these nutrients (mycorrhizal associations) has been known for a fair amount of time. You can even buy ‘mike’ preparations at the nursery to inoculate your perennial transplants. Some plants, however, depend on fungi for more than just minerals – they steal carbon (sourced directly from the air via the sun and photosynthesis in your typical green plant) from fungi. The extend of dependence on fungal carbon varies - from only during germination (possibly this is why Pink Wintergreen is so difficult to germinate - they need a certain fungus or two), to others such as Pyrola aphylla or certain leafless orchids (e.g. Corallorhiza maculata) that are completely dependent on mycorrhizal fungi – and their vascular plant hosts – for all of their carbon and nitrogen.
Sunday, June 20, 2010
I never would have expected it, but I have become quite obsessed with sawflies – those strange relatives of wasps and bees that cannot sting, have a saw-like ovipositor, have no wasp waist, and whose larvae look like caterpillars and mostly eat plants. In the Home Bug Garden, they seem to be determined to eat everything and are usually somewhere between interesting and devastating. Ergo, I am initiating a new tradition in the HBG: Sawfly Sunday. Now, what with the new Wildflower Wednesday, working full time, taking care of two gardens, and generally getting old and decrepit, I don’t expect every Sunday will have a sawfly posting, but my wife has collected quite a rogue’s gallery of creepy caterpillars not, and damaged plants. So here is the inaugural issue.
Monostegia abdominalis feeds on plants in the Primrose Family (Primulaceae) including loosestrifes (Lysimachia) and pimpernel (Anagallis arvensis) and was first described from Europe by Johann Fabricius (probably Linneaus’ most famous bug student). Actually, I should say plants that I was taught belong to the primrose family – apparently there are molecules that suggest these two genera would be better placed in the Myrsinaceae along with cyclamen – but in any case Linneaus described both plant species so we have a very tight origin of names here.
In Canada, our probable alien invader sawfly was first recorded on the introduced and naturalized garden plant Creeping Jenny (Lysimachia nummularia) around Ottawa and Montreal in 1965. In 1970, Peter W. Price – the famed insect ecologist who seems to have spent some time with the Forestry Research Lab in Quebec during his migrations from the UK to the USA – published a very nice study (Canadian Entomologist 102: 491-495) of our – lets call it the Creepy Loosestrife Sawfly – devastating a once unusually successful colony of the native Lysimachia terrestris around the frequently flooded margins of Caousacouta Lake in Quebec.
Now one might think that a loosestrife with the species name terrestris was more terrestrial than most, but it seems to be like most loosestrifes – they like boggy ground around water. Like most loosestrifes that I am familiar with, it has yellow flowers, so the common name Yellow Loosestrife is a bit useless. Swamp Candles is another common name and seems more evocative – especially if we want to build up some outrage that it is being eaten alive by an alien insect. However, the unusual success of Swamp Candles at Caousacouta Lake was due to artificial flooding by the local hydroelectric company creating an excess of suitable habitat. Without the flooding, the plant might well have been too uncommon to notice it being defoliated – and perhaps would not have been colonized by our Creepy Loosestrife Sawfly to begin with.
Peter Price’s paper has an excellent overview of the life history of the sawfly and its interactions with the native loosestrife. The sawfly had, more or less, two generations a year – but some larvae in the first generation hedge their bets and decide to wait until the next year to emerge from their underground pupation chambers. The second generation started in August in Quebec, but I suspect there is only time for one generation here in Alberta. Males are extremely uncommon and Peter suggested that our Creepy sawfly is thelytokous – that is females do not mate, but reproduce parthenogenetically. The females live only a few weeks but mature 30-70 eggs that they have available for sawing into the upper surface of the leaves of the loosestrife. The larvae will drop off the leaves if disturbed (I can vouch for that) and consume a tremendous amount of plant material (I can also vouch for that) – so much so that the loosestrife is mostly defoliated and many plants die. Or at least that is what was happening 40-odd years ago – I wonder what is happening at Caousacouta Lake now? Did the sawflies eat all the loosestrife and go locally extinct? Was the hydroelectric company forced to stop flooding the lake – what would that do to the dynamics? Has the loosestrife evolved resistance to the sawfly? One wonders if this isn’t an interesting historical entomology study waiting to happen.
Setting aside my minimal angst at the decimation of my Creeping Jenny (it was a free gift from Adrian, did far too well for the first couple of years, and now I don’t seem to need to worry about it becoming weedy), I do have a bit of worry about the sawfly’s ability to colonize native species. Dave Smith – the North American sawfly guru at the USDA with about 250 publications on sawflies - has a pdf plate on the web showing the adult, pupa and late instar larva and damage to the native fringed loosestrife. The fringed loosestrife (Lysimachia ciliata) is one of two loosestrife species that live around the lake at our place in the country (the other is Tufted Loosestrife Lysimachia thyrsiflora). They aren’t very common, so perhaps they are relatively safe – unless someone starts a loosestrife farm nearby and the overflow of Creepy sawflies eats them out. Also, I wonder if the sawfly isn’t the reason my expensive Variegated Golden Alexanders (Lysimachia punctata ‘Alexander’) disappeared from my bog garden. Hmm, just checked my notes and I’ll be buggered if it doesn’t say “cocked it Winter 2007-08, after sawfly defoliation 2007”. Bloody sawflies!
Wednesday, June 16, 2010
I have a friend who gardens on a grand scale on a large acreage in the country. He has a great appreciation for flowers of all sorts, and the larger or more exotic the better he likes them, but he can’t understand why people would want to plant wildflowers in their garden. ‘If you want to see wildflowers’, he says, ‘why not go for a walk in the woods?’
Well, whether or not that peculiar hypothesis turns out to be true, I have accumulated a fair number of both Alberta ‘native’ plants (i.e. allegedly part of the flora of Alberta before Europeans arrived) and North American native plants that may eventually have reached Alberta on their own, assuming our current inter-glacial period lasted long enough. Also, although I think blogging should be a recreation and not another chore, I could use a bit of a stimulus to post more regularly. So, I shall now embark upon a new tradition at the HBG: Wildflower Wednesday.
First up is something so native its provenance is Albertan and its name Canadian: Anemone canadensis, aka Canada or Meadow Anemone (Zones 2-9, moist to dry soil, shade to sun). Although its flowers are not as large as the domesticated Eurasian Snowdrop Windflower (Anemone silvestris), they are almost as showy and a similar bright white with yellow centers. Usually, Canada Anemone starts blooming here in late May, although this cold spring has held it up for a few weeks. The HBG has more shade than sun, but Canada Anemone tolerates shade well. In fact, it is probably a better plant in a shady garden than in a sunny one since it spreads by rhizomes and can be aggressive. The first sets that I planted came from a ranch in southern Alberta where the lady rancher was yanking them out of her garden by the handful. I’ve since added a local set from our place in the country because I’d read (Douglas & Cruden 1994 Amer. J. Botany 81: 314-321) that Canada Anemome is xenogamous – it is an outcrossing species that likes fooling around with alien pollen and doesn’t set seed well with its own pollen. The only pollinators that I could find records for were sweat bees (Halictidae), but the HBG has lots of halictids, like the Halictus confusus that graces the picture in the header.