What exactly is a weed? According to Merriam Webster a weed is: a plant that is not valued where it is growing and is usually of vigorous growth; especially : one that tends to overgrow or choke out more desirable plants. How do we decide what’s not desirable?
Washington State and many counties including King, have Noxious Weed Control Boards. They define and prescribe control of noxious weeds, a legal term for species that are difficult to eradicate, excel at spreading, and pose threats (note: noxious doesn’t mean poisonous). They have a tendency to take over landscapes and are graded based on their occurrence and potential in Washington. Having a specific legal term for troublesome weeds is necessary. “Non-native” doesn’t necessarily infer the need for applied control.
Of course not all weeds are catastrophic. Dandelions are a pain but they don’t threaten the welfare of our state’s agriculture. California poppies will take over an open area, but aren’t a serious threat in Seattle (though they are in Chile).
When it comes to Capitol Hill, most of the plants we encounter are not native. That doesn’t mean we need vilify them, they’re just plants afterall. They got here inadvertently, seeded in a bit of soil, they escaped from our gardens, or they were even introduced purposely. Scotch Broom for erosion control, dandelions for medicinal use, english ivy for looks. These plants spread because they are adaptable. They like disturbance (think construction), and have aggressive traits like long-living seed banks, voracious growth spurts, or production of chemicals that exclude other plants. Similarly, most have no biological controls outside their native ecosystems.
Their viability in our novel, urban ecosystem provides questions that aren’t answered easily. Some introduced species may never disappear despite best efforts. Should we just accept this and keep them from spreading? Focus on a few troublesome species? Embrace these alien scrambles of plants as a new ecosystem?
I’m not delusional. High rises will never sit alongside old growth stands with trilliums growing between cracks in the sidewalk. There’s little value in pining for the natural places that once were, where city stands. Despite this I am all for planting natives and ridding places like Interlaken of invasives because calling plants weeds inherently means one thing: we brought them, so we’re responsible.
You could get overwhelmed trying to rid your particular space of objectionable plants. Any fallow section of yard will inevitably attract a few and a neighbor’s neglected yard will act as nursery. Chemicals aren’t the responsible option, despite your not having time to spend weekends weeding. Major agricultural pests are often controlled by introducing a plant’s natural control insect to eat them but that’s a slippery slope and takes careful planning from experts.
Replacing the worst offenders with natives is unquestionably good. Simply put native plants provide food and habitat to native animals.The control boards above and the WSU extension service are good resources to learn more. They have the most current best practices for control, help identify problem species, and have a nice list of plants sold at nurseries that aren’t noxious but can be highly invasive. To get you started, below are some common, unwanted plants to focus on. With any of them, if caught early they are easier to deal with. The first two are vines that spread as one or several plants out. The second two spread by seed, so getting them in flower stops that risk.
- Himalayan Blackberry (Rubus armeniacus) – You know it because of the juicy blackberries it was brought here for, but it’s a bummer of a spiny vine, that’s difficult to remove.
- English Ivy (Hedera helix) - It’s evergreen, it grows rapidly, and can even kill gigantic trees by covering and choking them. It’s pleasant at first but you’ll regret letting it go.
- Herb-robert ( Geranium robertianum) - Gardeners used to plant this geranium. However, they like shade and take over our yards and wild spaces. They’ll quickly outpace other shade loving annuals.
- Scotch Broom (Cytisus scoparius) - They’re pretty in bloom, but takes over native prairies and very few native animals appreciate the dense fields it forms. The only proven method is to pull it up and their seed banks have been shown to lay dormant, in wait, for decades.
Previously in Pikes/Pines