Thursday, July 17, 2014

Summer Snowstorm

Look carefully for the "snowflakes" against the dark trees in the background
We're experiencing a "snowstorm" in the Pennypack Preserve this month.  Non-native Canada thistle (Cirsium arvense) (a real misnomer and a "slight" to Canada since this thistle is actually a native of Eurasia) has exploded in our grasslands.
The culprit in flower
All stages -  from flower to fluff
The incredible infestation is the result of a perfect storm of unfortunate events.  First, our boom sprayer was out of commission in the spring so Chris Dartley, our grassland manager, couldn't spray the thistle when it was most susceptible.  Second, the herbicide we've been using to try to control the thistle, Transline, seems to be losing its effectiveness, so we're going to have to find an alternative.  And third, by the time we realized the mess we were going to be in, migratory birds and rabbits had begun to nest in the fields, so we couldn't mow the thistle to prevent it from going to seed.
A patch with countless seeds
Non-native wineberry (Rubus phoenicolasis) cloaked in thistledown
Everything in the fields that's not green is thistle
One silver lining to these thistledown clouds: the American Goldfinches (Carduelis tristis) are having a field day (so to speak) feasting on the abundance.