On the sixth day of Christmas my true love gave to me, Six Geese a-laying. Geese led me to think about farms and all the delicious vegetables that grow there. But then I remembered that those lovely geese migrate, they move from location to location, just like some plants I know. Sometimes it’s not a good thing when plants migrate. They become invasive when they spread so quickly that they harm other plants and wildlife. Here are a few of those invasive plants in Washington State. Have you seen any of them in your yard???
Butterfly Bush Buddleia davidii This plant can re-seed like crazy. One cultivar produces an estimated 40,000 seeds per flower head! This plant is serious about continuation of the species. Newer hybrids are sterile, so don’t be afraid to plant these in the garden.
Purple Loosestrife Lythrum salicaria This one is even worse! A mature plant can produce 2.7 million seeds. Unbelievable! Purple loosestrife is an aquatic emergent plant and can be confused with the native spiraea and fireweed. A vigorous competitor.
Scotch Broom Cytisus scoparius In the spring you can’t miss this plant on the side of the road, it’s everywhere! Seeds are toxic to horses and livestock and remain viable for 80 years. These plants are here to stay. For most of these plants the best control is physical removal, ughhh!
Yellow Archangel Lamiastrum galeobdolon This semi-evergreen perennial has escaped from residential plantings into the surrounding forests and greenbelts. But then things get worse, it can grow in sun or shade. And then things get downright ugly, it reproduces from seeds as well as vegetatively. That means that any little piece of stem left behind will continue the bad news.
Himalayan Blackberry Rubus armeniacus This prickly problem costs millions of dollars for control and forms impenetrable thickets. It’s so persistent because it reproduces vegetatively from both root and stem fragments. Although I have enjoyed the delicious fruit, it’s dismaying to to see the dense tangles of blackberry covering yards and parks and over miles and miles across the Northwest.
English Ivy Hedera helix This plant loves the temperate climate in the Northwest and can out-compete many other plant species. English Ivy is an aggressive vine that can cover everything within its reach. I’ve seen too many trees covered by this ivy, shrubs shaded, forest floors carpeted. It’s daunting. At Stanley Park in Vancouver, B.C., the Ivy Busters estimate that in their first 39 “Ivy Pulls” more than 700 volunteers removed more than 20,000 square meters of ivy. They say it will take 50 years to rid Stanley Park of this invasive pest. I guess we have to start somewhere! Now let’s move on to the swans….