July’s Weeds of the Month: Dames Rocket and Leafy Spurge

After an unusually quiet June, the phones at TCWP have been ringing off the hook as Teton County residents watch the menacing flowering heads of Musk Thistle rising out of the surrounding vegetation. Roughly 75% of the urgent calls coming in are reporting a thistle of some kind, usually musk thistle. While we greatly appreciate these efforts from the community, we are also very concerned about other, less conspicuous weeds this time of year.

Weed of the Month, Number 1 Dame’s Rocket

Dame’s rocket was introduced from Eurasia intentionally due to its attractive purple flowers. It has been planted intentionally in flower gardens throughout Teton County where it does exceedingly well. Its aggressive root system and prolific seed production allows it to expand beyond property boundaries and “escape” into natural areas where it forms dense stands and quickly crowds out native plants.

Dame's Rocket
Dame’s rocket forms dense stands of purple, pink and white flowers that may look good in a garden bed, but not in a native plant community.
Dame's Rocket
Dame’s rocket is a member of the mustard family, which is characterized by 4-petaled flowers that grow in clusters. Other noxious weeds in this family include hoary cress, dyers woad, and perennial pepperweed.

Gardeners who like the look of Dame’s Rocket should consider planting Fireweed – a native plant that looks very similar.

Dame's Rocket Fireweed
Dame’s Rocket Fireweed

The apparent beauty of dame’s rocket makes it particularly malicious because most people don’t recognize it as a weed and instead welcome it into their gardens. TCWP is working to educate residents about the ecological damage this weed can do if it escapes in to natural areas and encouraging them to plant something native instead. Please report any dame’s rocket sightings to our office.

Weed of the Month, Number 2: Leafy Spurge

A second noxious weed that has our attention during this time of year is Leafy Spurge. This plant is in the Euphorbiaceae family, which includes a few ornamental plants you might find at a nursery as well as a few invasive species.

The spurges are hardy plants that are particularly appealing to gardeners because they contain a toxic milky sap that makes them unpalatable to deer.

Leafy Spurge Leafy Spurge

Leafy spurge is particularly aggressive because it is well-adapted to its homeland in the deserts of Eurasia where it has evolved an extensive root system (upwards of 20 feet deep) that it can regenerate from if the top is removed, and seed capsules that are capable of ejecting its seeds 15 feet from the parent plant. Leafy spurge finds the conditions in Teton County much gentler than they were in the desert and it is prospering in this environment.

Leafy Spurge
Leafy spurge can hitchhike in the root ball of a potted plant, resulting in it being “purchased” by accident from a nursery, as was the case with spurge that came with this Aspen tree
Leafy Spurge
Leafy spurge roots

Control of leafy spurge is very difficult. Its extensive root system makes mechanical control ineffective, and herbicide only works if it is absorbed into the root system – something that requires precise timing of application.

Leafy Spurge
Leafy spurge has not yet reached this level of infestation in Teton County and we are working to keep it that way.

Large infestations of leafy spurge are most effectively controlled by a combination of grazing by goats, fall herbicide application, and spring burning. At TCWP we are working hard to identify all infestations and “nip them in the bud” as soon as possible. This is one of a small number of noxious weeds that TCWP will treat on private property. Please call us if you see this weed.