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Our intern, Rhesa is supplementing her natural landscaping education by attending the series of workshops available by the East Multnomah Soil and Water Conservation District.  Here is what she learned from their Urban Weeds workshop. 

Lesser Celandine. Aww, what a pretty flower! True, but it will take over your garden if you’re not careful!


Weeds!! The scourge of gardeners, conservationists and lawn enthusiasts everywhere.  But what makes a weed… well, weedy?

It’s mostly a matter of “belongingness,” which depends one’s perspective.  On the one hand, a weed is basically any plant that is in the “wrong” place, which by some societal norms can mean non-native plants, and for others, it can be anything other than what you wanted to grow, especially when it comes to the monoculture of lawns.  

How ‘bad’ is your weed problem?

For many people, the ultimate most hated “weed” is the ubiquitous dandelion.  For others, dandelions are highly praised and even cultivated and enjoyed as medicine, food and a way to add nutrients to the soil as a dynamic accumulator.  

On the other hand, there are some ornamental plants we consider quite beautiful and so easy to grow. We excitedly share them with friends and neighbors and at plant swaps, only to realize that their very ease of spreading makes them a nuisance in a garden.  In some cases, certain weeds are actually detrimental to the wider ecosystem. A common example in our area is English Ivy, which spreads to the forests, choking out vital native ground cover wherever it grows.

Know your enemy!

This workshop helped participants to identify common weeds in our local area, with a particular emphasis on those considered invasive and noxious due to their negative effects on native flora and fauna and their habitat.  

Most importantly, we learned about how each weed spreads and the best practice for removing each one.  For instance, lesser celandine, the pretty yellow flower pictured above, spreads rapidly and can be difficult to eradicate for several reasons, including that they are ephemeral, meaning that they are only visible above ground for a short period, in the early spring.   Also, it spreads by seeds as well as their underground rhizomes and numerous bulbs. Their tiny brown bulbs often fall off the root when the plant is being dug up and each one of these grow into a new plant! Therefore, the specific advice given for removing this plant was to look out for the visible plants and flowers in early spring before they go to seed, and to carefully remove not only the plant but the soil around the roots to avoid the planting of new bulbs.  

There were many weeds discussed including periwinkle, pokeweed, bamboo, yellow flag iris, butterfly bush, Tree of Heaven, English holly, Himalayan blackberry, spurge laurel, yellow archangel, garlic mustard, giant hogweed, kudzu, Japanese knotweed- the last three of which require notification of local agencies for removal.  A great resource to be familiar with is the EMSWCD website, where you can find specific advice on the most difficult of these weeds at  While you’re there, sign up to take this or other upcoming classes on a variety of topics important to water and soil quality in our region.

What else can we do to reduce the spread of invasive weeds?

Consider that plants that volunteer easily and survive all types of weather have the potential to be invasive or at least a nuisance if they are not native to the area.  If you are like me, you’d be tempted to share these plants with others. One way to make sure, is to consult a weed list for your region like this source: , before adding new plants to your landscape.  And this includes wildflower seed mixes, as these can sometime contain aggressive plants like bachelor buttons.  Remember too that your shoes, clothes, pets, bike tires and car tires can carry weed seeds from one place to another. Clean off any seeds before and after going to a natural area to avoid spreading them.  And take frequent walks on your property, taking note of plants that have showed up as volunteers. That way, you can catch them early on before they have established or spread. Natural landscaping services such as those we provide at Common Sense Gardens, can go a long way in identifying problem weeds and keeping your yard free of invasive species.