Invasive weed: Cypress spurge

(Question)

I live in Norseman Heights in Etobicoke and have quite sandy soil. In the sunny parts of my beds, my garden has become overrun with what I believe to be Cypress spurge. I suspect it got a free ride into my yard about five years ago either on compost or a new plant. How can I best fight this pesky weed? Is there any option to use fungal or bacteria control and/ or leverage soil characteristics?

 

 

(Answer)

Cypress spurge (Euphorbia cyparissias) is indeed considered an invasive weed in Ontario. See Ontario weeds: Cypress spurge – note that there are 2 types of Cypress spurge in the province, one which is sterile and reproduces via its underground parts, and a fertile form that reproduces by seed as well as by underground parts.

The best method of controlling the spurge is by using a little muscle:

  • Mow the patches every 3 weeks to help control the plant. Ensure that you only mow when the plant is in its early flowering stage; once the seeds turn brown, you’d be spreading them.
  • Pull the plants out by hand and dig up the roots. This will take persistence, as the root system is extensive – spreading both horizontally and vertically. Dispose of these with city waste, do not compost at home. Use gloves, as the milky sap can be irritating to skin. Watch for new plants to pop up and get rid of them.
  • As with most weeds, another option is to use cardboard, newspaper or ground cover fabric to “starve” them of the light they need to survive. See our post, How can we keep weeds from regrowing?

Herbicides have been used, but these would likely not be permitted for use in home gardens (as this would be considered a cosmetic use). The City of Toronto’s Reducing Pesticides: Managing weeds the natural way  highlights pesticide-free ways of minimizing weeds – including pulling them by hand, planting other desirable plants to muscle the weeds out of the way, and feeding the soil. While the recommendations are not specific to the Cypress spurge, they should be helpful.

I located no information about controlling spurge using biological controls like fungi, bacteria or viruses. There seems to be some research about biological controls, but no recommendations for particular agents to use for the spurge.  Several species European insects were released in Canada (several years ago) as a means of biocontrol. Presumably, though, this has not impacted your home garden.

I have clumps of Cypress spurge in my garden, and keep these manageable by cutting/digging up roots. They are quite lovely in some spots. Also, my garden does not seem to spread the spurge to other nearby gardens.