Invasive Plants

The race to life at every level depends on disturbance and response, never on equilibrium. Every cell and seed jostles for existence. Their individuality evolves within a context that seems stable enough to be called a system, a coherent accommodation of disturbances.

Relatively rapid disturbances from outside a system are termed invasive. They upset our conservative consciousness unless, like each tilling of a field or building of a home, we emphasize beneficial gains.

Given the scope and acceleration of man-made change, what is the fate and value of native plant communities? Why, and how purely, should they be defended?

Queen Anne's Lace on the Halibut Point shoreline

Queen Anne's Lace, a non-native plant, has few detractors at Halibut Point. It graces the landscape with lovely and fascinating features. It takes hold in rugged terrain without appearing to be pushy. On the other hand it shows more of a tendency to colonize freely the grasslands of Cape Cod to the chagrin of nativist champions.

Dandelion

Dandelions, one of the most widespread plants introduced to America in colonial times, have situated themselves as liberally around the meadows of Halibut Point as they have Everyman's lawn. Yet they get a pass in The Invasive Plant Problem published on the Massachusetts government website. Its author Dr. Paul Somers distinguishes between being "weedy" and being "problematic in the more natural surrounding landscapes"-- a provocative notion to the homeowner but a thoughtful entry point to our topic.

Conversely, Black locust, Dame's rocket, and Yellow iris are among the plants gaining only slight ground at Halibut Point that have been categorized invasive by the Massachusetts Invasive Plant Advisory Group.



Black locust tree in flower on the quarry rim

Dame's rocket at woodland edge

Yellow iris in wetland

Local conditions have not allowed them to spread beyond toeholds in the Halibut Point landscape.

Phragmites, the Common reed, in meager quarters

Phragmites grows aggressively anywhere it can get a start in moist soil. It headlines any list of invasive plants but it too has garnered a limited presence at Halibut Point. The thin stand pictured here has attained only dwarf proportions in a damp swale by the seashore. It has achieved dominance in one wet spot by the parking lot but hasn't encroached on the swamp across Granite Street, perhaps shut out by the densely woven cattail root mass.

Human industry on the moors at Halibut Point

Much of the windswept open space on Halibut Point originally lacked enough soil to support agriculture or pasturage. Indigenous plants there remained relatively undisturbed by human occupation and re-colonized the moors after granite quarrying ceased.

The native Rosa virginiana at home on thin soil

Within this tangle of hardy shoreline creepers the Virginia rose has succeeded over species less drought and salt-resistant.

Rosa multiflora sprawling on old pasture land

Exotic plant species find easier entry on the arable acres once cleared for farming. Upland re-naturalization over the last eighty years has incorporated a mix of novelties among the natives. Free-seeding Rosa multiflora that had been imported from Japan to stabilize eroded American landscapes has established extensive thorny thickets. They are opportunistic but not necessarily invasive in the sense of intruding on vulnerable ecologies, since pre-existing systems had been eradicated. Much of the State Park is progressing through successional stages toward a mature woodland that will resemble but not replicate the original forest. There will be additions, subtractions, and new proportions.

The fruit of Oriental bittersweet showcased on the old barn

Many of the introduced plants had useful or attractive features. In some cases their damnable vigor was part of their initial appeal. 


Bittersweet vine enmeshing a cedar tree,along with poison ivy

Oriental bittersweet's behavior turns thuggish as it suppresses the innocent trees that it utilizes as scaffolds to sunlight. 


Catbrier blanketing shrubbery

But then native catbrier and grape similarly smother anything they climb on, until ultimately shaded out themselves by the light-excluding canopy of the maturing forest.

Grape vine surmounting a tree

It's the instinctual way of natural increase, and it characterizes recent centuries of human dominion on the land. Imagine substituting the word 'cultures' for 'plants' in this statement on the Mass.gov website: "Exotic, invasive plants create severe environmental damage, invading open fields, forests, wetlands, meadows, and backyards, and crowding out native plants." In the mirror of history Homo sapiens is the most invasive species of all.

Our enterprise has intentionally or inadvertently affected all life on earth. The flora of Halibut Point is more diverse than ever as newcomers have filtered in. But bio-diversity worldwide is declining as species are driven to extinction. The consequences have ethical and practical dimensions.

Purple loosestrife at the edge of a cattail stand

A few decades ago, as many people were enthralled by purple loosestrife's vivid transformation of local wetlands, it dawned on close observers that this escaped European species was dooming other parts of the ecosystem. Importation of beetles that feed on loosestrife in their native lands has checked the invader to non-threatening numbers apparently without collateral damage. This biological re-balancing represents a success story in environmental intervention. The preservation of wetlands has particularly active allies.

Part of the refreshment of wild spaces is that their dynamics are not managed by human hands. Their internal aspirations and tragedies proceed awesomely beyond our control, design, or prayers. The fittest or luckiest survive in an incalculable web of neighborly invasions.

It seems unlikely that we could reverse the influx of non-native plants in the public landscape even with the mobilization of Maoist level political will. The plant communities will have to reach their own accommodations with selective management for sanctuaries of special interest or rarity.