Invasive Shiny Geranium

In recent years, the small ground-covering invasive annual called “Shiny Geranium” (Geranium lucidum) has been spreading on Salt Spring Island. Patches of the weed are currently found on Quarry Drive Park, at the corner of Lower Ganges Road and Booth Canal, on the Vesuvius-Margaret trail by the ferry, and, the worst spot, on the old Vesuvius Inn land. It has also been reported near Yeo Point (north of Ruckle Park), between Canvasback and Tripp Rds., and near the Reginald Hill trailhead.

Here on the pacific northwest, Shiny Geranium’s leaves are up for most of the year, even through winter, very green and could flower as early as February. Shiny Geranium is difficult to tell from Dove’s Foot Geranium (another non-native invasive species) except that the stems of Shiny Geranium are smooth, not hairy.

Shiny Geranium springs up in moist soil, sun/shade and moisture conditions, and thrives in woodlands and forest glades, where it tends to overwhelm native plants. It grows up to 14” tall; in favourable conditions, the top stems can be green, though the base and seedlings are deep red.

Removal

Shiny Geranium is easy to pull from the soil but do not compost it, as seeds can continue maturing after plants are picked. Instead, try our preferred method of “solarizing” – seal plants in a clear garbage bag and leave it in the sun. This exposes the plants to very high heat, which kills the seeds and plants. Alternatively, the bagged plants can be put in the garbage or labelled “Invasives” and taken to Hartland.

A flame torch can be used on growing plants. Shiny Geranium is an annual plant, so its roots do not need to be removed (please follow fire safety protocols).

Shiny Geranium is a winter annual, otherwise known as a cool-season annual, hardy annual, and frost-tolerant annual. Typically, winter annuals drop their seeds late spring to early summer; seeds germinate in the cool, moist conditions of late summer and fall; the new plant typically, but not always, produces a rosette of leaves in the fall. In our coastal climate, these plants may continue to grow through much of the winter, with a growth surge in early spring, and complete their life cycle well before summer. Many of the weeds that behave as winter annuals may also germinate in early spring, long before the summer annuals.

Invasive weeds take advantage of this cycle as few native species do, giving them a ‘jump’ on establishing themselves before the ‘locals’ can grow quickly enough to compete with them.

Examples of other invasive winter annuals outside of the Geranium family using the same growth strategies include annual Bluegrass, Corn Spurry, Chickweed, Shepherd’s Purse, Red Deadnettle, Speedwell, Groundsel, Redstem Stork’s-Bill, and Garlic Mustard.

The Garry Oak ecosystem includes the following three winter annuals: Farewell-to-Spring (Clarkia amoena), Small-flowered Blue-eyed Mary (Collinsia parviflora) and Sea Blush (Plectritis congesta). Blooming early in spring, they drop their seeds by the end of June, germinate in the fall, and create low, green carpets of small foliage over the winter, ready to sprout up quickly in early spring.

This 2023 video about Shiny Geranium by Wylie Thomas, Conservation/Restoration Biologist in Oak Bay, is an eye-opener for gardeners:

Similar Invasive Species

Dove’s Foot Geranium (Geranium molle)

Dove’s Foot Geranium has leaves very similar to the shiny geranium in shape, however, they are not as glossy, making them less visible. The flower petals can help with identification. The dove’s foot petals have rounded edges with shallow clefts, making them look as though a single petal is two.

Herb Robert (Geranium robertianum)

Easily distinguished by its distinctive and strong leaf odour when touched or pulled out. The leaves are not typically geranium-like; instead of being rounded and deeply lobed, Herb Robert’s leaves are more triangular in shape, with 3-5 segments. The flowers are similar to those of shiny geranium, with rounded petals.

Crane’s Bill, Cut-leaved Geranium (Geranium dissectum)

The deeply clefted leaves of this European invasive plant are the distinguishing feature of this geranium species. The petals have a shallow notch, making it appear mallow-like.