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A Year in the Life of Pimmit Run: The Invaders

Here it is June and we have seen so many wondrous natural sights in the stream valley so far this year. But there is a dark side that tries to take over this time of the year - the invasives, which, if left unchecked, will destroy what nature has to offer.

Looks pretty but many invaders lurk within

Why do we care about invasive plants? Once they move in, they grow rampantly and negatively impact native plant and wildlife habitat. They create a monoculture that destroys the plant biodiversity that our ecosystem needs to thrive. And in the worst case, they actually choke and kill our precious native trees.

In my spare time I am the Fairfax County Invasive Management Area (IMA) Site Leader for this portion of the stream valley trail and I have been stalking and documenting these invaders for some time. The counterattack is underway, but it will be a long slog. All of the invasives listed below are apparent in the stream valley and many are growing rampantly. Let's go on a tour and see what a few are up to. Warning -- it can get scary.


Autumn Olive (Elaeagnus umbellata)

Bamboo (Bambusa, Phyllostachys and Pseudosasa)

Bush Honeysuckle (Lonicera species)

Garlic Mustard (Alliaria petiolata)

Japanese Barberry (Berberis thunbergii)

Japanese Honeysuckle (Lonicera japonica)

Japanese Knotweed (Polygonum cuspidiatum)

Japanese Stiltgrass (Microstegium vimineum)

Lesser Celandine (Ficaria verna)

Mile-a Minute (Polygonum perfoliatum)

Multiflora Rose (Rosa multiflora)

Oriental Bittersweet (Celastrus orbiculatas)

Porcelain Berry (Amphelopsis brevipedinculata)

Winged Burning Bush (Euonymous alatus)

Wintercreeper (Euonymous fortunei)

Wineberry (Rubus phoenicolasius)

Wintercreeper (Euonymous fortunei)

Wisteria (Wisteria floribunda, Wisteria sinensis)

At any given time I am on the warpath against the invasive of the day. Right now it's Wisteria (Wisteria floribunda, Wisteria sinensis) which is taking over a huge treasured streamside area affectionately referred to as the "swimming hole." It sends its huge vines up and around the native trees, choking them, and the smaller Wisteria growth covers the forest floor, smothering the native flora. A few weeks ago a group of us liberated countless trees in this vicinity, but much remains to be done.

Wisteria choking a mature native tree (thankfully, we cut the vines, but the tree may be gone forever)
Wisteria grows fast, but this didn't happen overnight

Next up is Multiflora Rose (Rosa multiflora), which lines many portions of the trails, particularly at the park entryway. A group of us cleared a huge area of Multiflora Rose at the park entrance recently, revealing a sweet hidden groundlayer of Woodland Stonecrop (Sedum ternatum).

A pile of Multiflora Rose off to the trash heap

Winged Burning Bush (Euonymous alatus) is tenacious in the park, if nothing else. Here is a picture of it in tree form, actually growing right out of a large rock. This one is destined to be sawn off at the earliest opportunity.

Hand me a saw, quickly, please

I'd be remiss if I didn't mention the Bamboo (Bambusa, Phyllostachys and Pseudosasa). Ah, Bamboo. There are at least two huge patches of it along the stream valley trail. But it takes an army, complete with bobcats and chain saws, to deal with this monster invader, so no telling when that fight will occur.

Waiting (in vain) for an army to deal with the Bamboo

As lovely as the picture below is of the new Wet Meadow portion of the stream valley trail, a closer look reveals massive infestations of Porcelain Berry (Amphelopsis brevipedinculata) in the meadow, Japanese Knotweed (Polygonum cuspidiatum) in dense thickets along the streambank on the right, and Bamboo (Bambusa, Phyllostachys and Pseudosasa) on the upper left.

Dealing with the invasives in the Wet Meadow will be no walk in the park

Some invasives are scarier than others. Catching a glimpse of Mile-a Minute (Polygonum perfoliatum) brings a shiver to my spine. It looks kind of sweet here but don't be fooled. It is one of the most horrible invasives to remove.

Mile-a Minute: touch without gloves and you will regret it

Last but not least is the insidious Lesser Celandine (Ficaria verna). In early spring it carpets the forest and floodplain floor, and the unaware praise its blanket of yellow flowers. But it displaces the equally beautiful and infinitely preferable native species.

Lesser Celandine along the floodplain floor -- lovely, but deadly to native species

This has just been a quick review of some of the worst of the worst along the stream valley. One of the joys of reclaiming an area previously infested with invasives is seeing what native species pop up on their own when liberated. I look forward to making lots of delightful discoveries as we free the park from these invaders.


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