Nova Scotia: A Bog on Cape Breton

Perhaps this sign at the head of the Bog Trail, near the western edge of Cape Breton Highlands National Park, would not inspire everyone to take a stroll, especially in the mild drizzle that was falling when we pulled up to the trailhead on June 6, 2012.  I was the only one of our party that wanted to attempt it - but I found it one of the most fascinating and rewarding stops of our entire tour.

Bogs can remarkable places for botanising, but getting into the heart of one can be a messy procedure.

The trail itself is short - it only takes about 15 or 20 minutes to circumnavigate - and fortunately walking it couldn't be easier: a boardwalk runs around the whole thing, giving me a chance to get on close terms with the vegetation without getting my feet either muddy or wet.

The key ecological point about a bog is its acidic, nutrient-poor soil.  Plants that grow in a bog have to be acid-tolerant, and in its wetter areas may have to rely on special mechanisms to get the nutrients, particularly nitrogen compounds, that they need for growth.  That is one of the reasons why bogs are good places to find carnivorous plants - in this case, Northern Pitcher Plant (Sarracenia purpurea).  We'll look more closely at the bog's carnivorous plants below.

The chief contributor to acid buildup in a bog is the peat layer, often many metres deep, that develops from the decay of its underlying growth of sphagnum mosses (Sphagnum spp.).

Horsetails (Equisetum spp. - I'm not sure which one this is), like mosses, have been around for a very long time.  They are not mosses, but spore-producing vascular plants related, more or less, to ferns.

The trees around the edge of the bog are largely Tamarack (Larix laricina), one of the few deciduous conifers.  Like the horsetails, it is not so much that Tamarack is acid-adapted, but that it is so broadly soil-tolerant that it can as well in bogs as in other places, and indeed it is usually the first tree to invade a peat bog as it fills and reverts back to forest.

In the shrubbier parts of the bog grow plants with surprisingly attractive flowers.   They are, frequently, members of the acid-tolerant heath family (Ericaceae).  Here is one example.  It may not quite look it, but this is a species of Rhododendron: Rhodora (Rhododendron canadense).

 The name reflects its rather un-rhododendron-like appearance; botanists once placed it in a separate genus, Rhodora.  It is a common plant around wetlands in eastern Canada and New England; Ralph Waldo Emerson once waxed rhapsodic about it, calling it a "rival of the rose".  It's certainly very pretty.

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Even more attractive, to my eye, is Bog Laurel (Kalmia polifolia), another shrubby heath at home in a northern bog.  Its flowers are obviously popular with the local insects.

A very similar species Sheep Laurel (Kalmia polifolia) may grow here too; among the chief differences are the arrangement of the leaves - usually opposite in Bog Laurel, usually whorled in Sheep Laurel (which is also a larger and shrubbier plant). I think this one is still Bog Laurel, but it could be Sheep Laurel - are there any botanists in the audience?

Bog Rosemary (Andromeda polifolia) is a peat-bog specialist that grows around almost the whole of the northern hemisphere.  It is another heath, quite unrelated to the common kitchen herb (which is a species of mint) despite the superficial similarity of their leaves.

One more heath - and another rhododendron: Labrador-Tea or Bog Labrador-Tea (Rhododendron groenlandicum). Despite the name, this is much more of a typical rhododendron than Rhodora – something that would be more apparent in these photographs if the buds had been in full flower. The English name refers to the Native American custom of brewing its leaves for tea (and as a medicinal drink); in Europe, where the plant also grows, it was once used as an additive in the brewing of beer.

Buckbean or Bog-Bean (Menyanthes trifoliata), another bog-adapted plant widespread through much of the northern hemisphere, is not a true bean but a member of small family of five genera of aquatic plants, the Menyanthaceae, related to the gentians (and including the familiar Water Snowflake (Nymphiodes indic a)).  The leaf and flower shoots arise from submerged, creeping rhizomes.

Common Cottongrass (Eriophorum angustifolium) isn't a grass (or a cotton) but a sedge.  There are a number of species of Eriophorum, and I am only assuming this is E. angustifolium.  Cottongrasses can be abundant in northern hemisphere bogs and, in particular, on the arctic tundra (another region with nutrient-poor, acidic soils).

Finally, we come to the most unusual of the bog plants, the ones that supplement their diet by trapping and, more or less, devouring insects and other small animals. This is a Round-leaved Sundew (Drosera rotundifolia), a member of a worldwide family of almost 200 species whose leaves have evolved into a sort of living flypaper. Each long hair arising from the leaf tip ends in a gland that releases a sweet, sticky glob of liquid that both attracts insects and traps them.  In most sundews, the leaves are able to curl slowly around their victim, trapping it in as many globules of glue as possible. The glands also secrete a number of digestive enzymes that allow the plant to feed from its prey.

The pitcher plants on the Bog Trail, unlike the sundews,  do not belong to a worldwide family. Their family, the Sarraceniaceae,  has only three genera, two in North America and one in South America. The pitcher plants so familiar in Malaysia belong to a different family, the Nepenthaceae,  and there is disagreement among botanists as to how closely the two families are related. One of the standard classifications puts both families with the sundews and some other non-carnivorous families, into a single order, Nepenthales, while another scatters them more widely throughout the flowering plant kingdom.

 Both of the insect-eating plants on the Bog Trail have reddish rather than green leaves – presumably for the same reason that flowers are brightly coloured: as lures, not, in this case, for pollinators but for victims.

 While the pitcher of Nepenthes pitcher plants involves only the tip of the long, drawn-out middle portion of the leaf,  the insect traps of the Northern Pitcher Plant ( and of the other, also unrelated, plant to have developed an insect-catching pitcher, the Albany Pitcher Plant (Cephalotus follicularis) of southwestern Australia) involve almost the entire leaf. Notice the downward-pointing hairs on the inside of the lid, adaptations to prevent any victim that has fallen into the pitcher from climbing out again.

 I was not at the right time of year to see the pitcher plants in bloom, but I did find a few dried flowering stalks. The individual flowers are considerably larger and  more showy than those of Asian pitcher  plants, and have a most peculiar structure.  The large, somewhat umbrella-like object at the tip of these dried flowers is the style, grossly expanded to form a basin that catches pollen falling from the anthers. Blowflies that crawl into the inside of the umbrella seeking nectar soon become coated with pollen that they carry to another flower – presuming, of course, that they do not fall prey to another pitcher plant, or to a sundew, first.  Some plants will do anything for nitrogen.