Colossal Coastal Cottonwoods

BC's Champion Black Cottonwood, Fraser River, R. Kelman

Black cottonwoods (Populus balsamifera spp. trichocarpa) are the largest and tallest of the poplar family. I know these distinctive, broken-limbed, trees from my birthplace in southwestern Alberta. There at the end of the prairies, in the bottom lands of river valleys, grow centuries old, twisted cottonwoods. The trees are surrounded by collections of major limbs, broken off during strong winds or after heavy snowfalls.

One of the rituals of the prairie spring was hiking in the river valley and smelling the sweet resinous buds of the cottonwoods opening. The buds contain a waxy resin with anti-infectant properties still used in many modern natural health ointments. Later, the mature cotton-like seeds coat the ground in such abundance that they look like snow.

Cottonwoods near Lethbridge, AB
Photo: Belle Hughes

I often watched Great Horned Owls roosting on their favourite large cottonwood branches, and collected their bone-filled pellets at the base of the wide, grey trunks. But these prairie cottonwoods are small compared to those growing on the western end of their range on the BC coast.


Range of The Black Cottonwood

The prairie cottonwoods are at the eastern limit of their range.  This western species of broad-leafed deciduous tree inhabits coastal regions from Alaska to southern California, as well as western inland regions.

Range of Black cottonwood

Although cottonwoods are found throughout BC, they are rare on the outer coast of Vancouver Island, and all of Haida Gwaii. I do not commonly see them on my tree outings in the south island area, but if you know where to look they can be found.

Champion Cottonwoods

None of BC's champion cottonwoods are on Vancouver Island. The biggest cottonwoods in the province are on the Fraser river floodplain near the city of Vancouver. 6 out of the 10 largest recorded specimens in the province are on Skumalasph Island on the Fraser River close to Chilliwack.

Conditions are particularly suited to these trees here since poplars enjoy seasonal flooding, a mild climate, heavy nutrient load from salmon runs, and a long growing season. In these primo conditions cottonwoods reach truly massive proportions.

World's Largest Cottonwood, Fraser River, R. Kelman

BC's current listed champion Black Cottonwood (BC Big Tree Registry) is found at the confluence of the Sumas and Fraser Rivers. It is noted as the world's biggest poplar, and its measurements are indeed impressive.

Circumference: 11.92m/39.5ft
Height: 39.01 m/128 ft
Crown spread: 29.60 m/97ft
AFA Points: 626

This tree takes top spot in all measures except height, which is beaten by a champion cottonwood in the Skagit River Valley (two hours east of Vancouver along the US border). This beautiful specimen is 57.61m/189ft tall. The big trees here are protected in a 28,000 hectare provincial park.

Cottonwood Ecosystems

Cottonwoods require ample moisture and plenty of nutrients to grow well. They favour floodplains and rich, moist sites with plenty of light, and can also be found in open areas on lake shores.

Leaves and seed pods

Although mostly considered a weed by the logging industry, this amazing tree is an integral part of the watersheds it inhabits. Where it occurs on seasonally wetted alluvial islands and floodplains, the black cottonwood acts as a massive nutrient pump, drawing up and storing nutrient-rich water. They stabilize the ground on which they grow, and redistribute nutrients back to the land and water.

Cottonwoods also provide important habitat for eagles as one of few trees that are large enough for eagles to use for nesting and perching. They are also used by cavity nesters such as Northern flickers. Bats roost under loose sheets of ancient, peeling bark on old, dead, standing trees. Bears den in their hollow trunks, sometimes a couple of meters off the ground.


Mapping the Cottonwood Genome

In 2006, the cottonwood became the first tree to have its genome mapped. This is a famously fast growing tree (up to 2m/6ft per year in young trees), and scientists hope to isolate the gene responsible. With this knowledge they plan on making fast growing Frankentrees to grow on mono-cropped fibre farms where our amazing, diverse forests used to be. Such trees are destined for 'sustainable' biofuel production.

"Analyses suggest that one of the most efficient and sustainable methods of biofuel production will be harvesting the above ground portions of densely produced, fast-growing perennial energy crops such as poplar trees (Populus trichocarpa)."

- L. Bartley, Biofuel production

In a more progressive use of cottonwood genetics, scientists are experimenting with their petri-dish productions in order to grow trees that can clean contaminated industrial sites. Scientists hope to use the cottonwoods water pumping abilities to absorb toxins out of soil.

Where to Find Black Cottonwood on Vancouver Island
 

Black Cottonwoods, Langford Lake

Black cottonwoods on Vancouver Island can be seen on river floodplains, especially along the east coast. Rivers such as the Puntledge or Tsolum rivers are good bets, as is the Oyster River, which reportedly has some impressive trees.

On the south island, three are nice trees at Goldstream Provincial Park along the Goldstream River, particularly the 300 year old trees around the nature house next to where the river empties into the sea. Langford Lake also has some cottonwoods at various locations, including some that are accessible by public trail.

Black cottonwood, Goldstream River

Cottonwoods are normally about 30 m/60ft tall with greyish deeply furrowed bark. They have waxy leaves, sticky buds, hanging groups of seed pods, and puffy seeds that travel on the wind and in moving water. In the spring you can use your nose to follow the bud's sweet odour to find the trees. The trees distinctive odour can be detected up to 100 meters (300 ft) away.