Several weeks ago I spent a typical Portland winter morning (i.e. grey, drizzling, and chilly) participating in a local Friends’ group volunteer event to pull weeds along a restored stretch of an urban stream. Most of the weeds plaguing this site are non-native invasive species that either successfully resisted previous removal efforts or crept back after restoration. Every state is cursed with its own particular rogue’s gallery of invasives, and the ones we fight here in Oregon include Himalayan blackberry (Rubus armeniacus), English ivy (Hedera spp.), English holly (Ilex aquifolium), and the plant that really puts the “noxious” into noxious weed, reed canarygrass (Phalaris arundinacea).
Himalayan blackberry was introduced as a crop plant from Europe in the 19th century, and it certainly provides an abundance of tasty fruit, but it’s also armed with flesh-shredding thorns that make it a plant equivalent of the Wolverine, and it grows so quickly and in such impenetrable tangled mats that it out-competes every other plant in the understory. English ivy is a regrettable ornamental with little habitat value that also escaped cultivation and spread rapidly as a habitat-choking groundcover and a vine that can cloak shrubs so throughly they may eventually die because sunlight can’t reach their leaves. English holly, another European escapee, is beloved by birds for its bright red berries, which are also unfortunately carried into forests where they give rise to dense thickets that suppress germination and growth of native shrubs and trees. Reed canarygrass, a perennial that grows 3-6 feet tall in crowded monocultures, is a major threat to northwestern wetland ecosystems that resists removal by heavy machinery (copious seeds and rhizomes simply grow back) and various herbicides (control is effective only for a few years, after which treated areas are re-invaded)
Himalayan blackberry was introduced as a crop plant from Europe in the 19th century, and it certainly provides an abundance of tasty fruit, but it’s also armed with flesh-shredding thorns that make it a plant equivalent of the Wolverine, and it grows so quickly and in such impenetrable tangled mats that it out-competes every other plant in the understory. English ivy is a regrettable ornamental with little habitat value that also escaped cultivation and spread rapidly as a habitat-choking groundcover and a vine that can cloak shrubs so throughly they may eventually die because sunlight can’t reach their leaves. English holly, another European escapee, is beloved by birds for its bright red berries, which are also unfortunately carried into forests where they give rise to dense thickets that suppress germination and growth of native shrubs and trees. Reed canarygrass, a perennial that grows 3-6 feet tall in crowded monocultures, is a major threat to northwestern wetland ecosystems that resists removal by heavy machinery (copious seeds and rhizomes simply grow back) and various herbicides (control is effective only for a few years, after which treated areas are re-invaded)
Himalayan blackberry, scourge of the Northwest. Photo by C.A. Searles Mazzacano. Controlling invasive species, especially in urban areas that experience continuing disturbance and high visitation by humans and pets that spread seeds and propagules, is an ongoing and often contentious issue. Use herbicides as a necessary evil to knock back the invasives and hope the natives thrive? Go organic instead and find enough willing volunteers (which in Portland often includes goats, who eagerly consume Himalayan blackberry) to keep invasives under control long enough for newly-planted natives to gain a root-hold? This dilemma drifted through my mind as I stood on the bank of a creek that just five years ago had a terribly degraded riparian zone, consisting of a few scattered cedar trees surrounded by a sea of reed canarygrass and ivy. Now I gazed out on a vastly different scene, a functional riparian zone dominated by native plants, where tumbles of jewelweed edged banks shaded by red osier dogwood, willow, and alder. Invasives persist, though in much lower numbers, primarily in patches where native plantings failed (or were chewed to nubs by urban beavers) or where restoration was not yet complete. I went to work on one of these patches, standing in several inches of cold water while slamming a pickax into a clump of reed canarygrass clinging stubbornly to the bank. After several minutes of vigorous pickax application I managed to hack loose a few square inches of the dense root mass, which repaid my efforts by spattering me thoroughly with icy mud as I heaved the startlingly heavy weight up onto the walkway for disposal.
As I stood in the rain trying to recover enough feeling in my fingers to wipe the mud off my glasses, the head of the Friends group remarked that reed canarygrass had been awful originally, covering the banks and spilling into large mats in the stream itself. When I asked what nuclear device had been deployed to knock the pestiferous plant back to its current low levels, she replied that it was done entirely by groups of volunteers who waded into the river with knives and axes, chopping the mats free and hauling them to shore for disposal. I felt a little thunderstruck as I did some mental calculations to scale up the effort needed to remove a single chunk of this weed, and then I realized—this is why I volunteer. Groundwater is being pumped dry, wetlands are being filled and degraded, rivers are being dammed and polluted, endemic insect species are going extinct as I type this, and in the course of my life, I can only only stem the tide of destruction for what feels like an increasingly and depressingly tiny proportion of the planet. But “action is the antidote to despair”, as Joan Baez is credited with having said, and here and now in my own watershed, I can straighten my aching back, blink sweat and rain out of my eyes, and share some scones with a small group of people looking out contentedly on a patch of habitat that we made better for the wildlife and people who live here now, and for a generation to come.
As I stood in the rain trying to recover enough feeling in my fingers to wipe the mud off my glasses, the head of the Friends group remarked that reed canarygrass had been awful originally, covering the banks and spilling into large mats in the stream itself. When I asked what nuclear device had been deployed to knock the pestiferous plant back to its current low levels, she replied that it was done entirely by groups of volunteers who waded into the river with knives and axes, chopping the mats free and hauling them to shore for disposal. I felt a little thunderstruck as I did some mental calculations to scale up the effort needed to remove a single chunk of this weed, and then I realized—this is why I volunteer. Groundwater is being pumped dry, wetlands are being filled and degraded, rivers are being dammed and polluted, endemic insect species are going extinct as I type this, and in the course of my life, I can only only stem the tide of destruction for what feels like an increasingly and depressingly tiny proportion of the planet. But “action is the antidote to despair”, as Joan Baez is credited with having said, and here and now in my own watershed, I can straighten my aching back, blink sweat and rain out of my eyes, and share some scones with a small group of people looking out contentedly on a patch of habitat that we made better for the wildlife and people who live here now, and for a generation to come.
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