Why bother learning the names and features of plants? In my experience, learning the names of various species and how to identify them has brought increased detail to the variety of life around me. Furthermore, an awareness of invasive species can aid in efforts to manage them. Invasive species reduce biodiversity on Mayne Island, threatening native species with a reduction in water, nutrients, and space.

Some plants look very similar and can be hard to tell apart. In this article, I will highlight a selection of plants and describe how to tell them apart from their lookalikes. Distinguishing between an invasive plant and a lookalike native is especially important when managing invasives.

Scotch broom (Cytisus scoparius) and gorse (Ulex europaeus)

The invasive gorse shrub hasn’t been established on Mayne Island yet, as the few plants that were found were eradicated. However, it is nearby on Galiano, South Pender, North Pender, Salt Spring, and Saturna. It’s essential to keep this plant from spreading by seed to Mayne. Early detection and rapid response are our friends in preventing the establishment and distribution of invasive species on Mayne Island. Gorse looks similar to Scotch broom but has black hairy branches and spines, while broom doesn’t. Please report to the conservancy if you find gorse. While the vibrant yellow flowers of gorse and Scotch broom are striking, they reduce biodiversity by out-competing native plants and are fire hazards with high oil content that is very flammable.

Coming from Victoria, I’ve seen yellow seas of invasive Scotch broom taking over disturbed roadside sites. This all comes from just three broom plants planted in Sooke in 1850 by a nostalgic Scottish mariner. Within the parks the conservancy cares for on Mayne, there is a stark contrast between the park boundary, where Scotch broom has been managed, and where private property lines begin (and broom often flourishes). I see this positively, however, as it shows the impact many dedicated hands can make toward retaining pockets of diversity within green spaces.

Spiny gorse plant. Photo taken by cirkel der natuur.
Scotch broom lacks spines. Photo taken by Andreas Rockstein.

Sweet-briar rose (Rosa rubiginosa) and Nooka rose (Rosa nutkana)

Invasive sweet-briar rose can be differentiated from the native Nootka rose by its curved thorns. Nootka rose also tends to have a more vibrant red, dark stem whereas sweet-briar has green to bluish stems. If in doubt, leave the plant to grow for longer, and the curved thorns will become more apparent. The deer browse conditions on Mayne Island have reduced native species’ ability to compete with invasives, likely advancing the spread of sweet-briar on Mayne.

Invasive sweet-briar rose showing curved thorns. Photo taken by Andreas Rockstein.
Native Nootka rose showing straight thorns. Photo taken by Cohen Muters.

Himalayan blackberry (Rubus armeniacus) and trailing blackberry (Rubus ursinus).

Invasive Himalayan blackberry forms dense, impenetrable thickets. It has three leaflets on shoots that bear flowers or berries, five leaflets on vegetative shoots, and a four-angled stem. The native trailing blackberry has only three leaflets on all shoots, and a smoother stem. So, if you see a blackberry shrub with five leaflets, you know it’s invasive Himalayan.

Himalayan blackberry with five leaflets and a four-angled stem. Photo taken by naturgucker.de.
Trailing blackberry with three leaflets. Photo taken by Yaz Obara.

English hawthorn (Crataegus monogyna) and black hawthorn (Crataegus douglasii)

The invasive English hawthorn has red berries and deeply lobed leaves like an oak tree. The native black hawthorn has purple black berries and oval leaves with saw-toothed margins. Black hawthorn has many traditional uses, such as the thorns being used as prongs on rakes to catch herring, and the hardwood for tools and weapons. The scientific name comes from the Greek word kratos, meaning strength.

Though the native black hawthorn occurs infrequently on Mayne, the Conservancy has successfully established new populations in restoration sites at St. John Point Regional Park, Bennett Bay, and Hedgerow Farm wetland.

English hawthorn with deeply lobed leaves. Photo taken by Andreas Rockstein.
Black hawthorn with oval leaves. Photo taken by Wendy Cutler.

How can you help?

Consider taking action on your property by removing invasive species. If you have a fenced garden (to keep out the hungry deer), you could also plant native species. The Mayne Conservancy has a selection of plants for sale from our native plant nursery. Also, see the invasive species removal tips below.

The Mayne Island Conservancy’s Native Plant Nursery.

Make use of the Mayne Conservancy’s free Landholder Consultation Program, where you can learn about the natural features of your property, identify plants and animals, and receive advice on native planting and invasive plant management.

Join our habitat restoration group to get emails on our ongoing volunteer restoration events.

Removing Himalayan blackberry during a habitat restoration event.

Removal Tips:

Check out our guide for manual removal methods for common invasive plants of Mayne Island here.

Check out our Invasive Plant Management Workshop Recording here.

All restoration sites should be revisited and monitored for the regrowth of invasive species in subsequent years.

You can dispose of the removed plants by composting them in a pile in a preferably shady area, piled high to limit the footprint. Monitor Himalayan blackberry compost piles, as they can resprout in wet conditions. Burning the piles can be considered if they are in a suitable location, and local Fire Department procedures are followed.

Scotch broom will not re-sprout from root tissues. Therefore, cutting below the uppermost root will kill the plant. This is preferable to digging out the roots, which disturbs the soil, stimulating more seeds to germinate. If the stem is too big to cut below the uppermost root with loppers, cut 5-10 cm above the ground with a hand saw, and then split the stem with an axe.

Sweet-briar rose should be cut back with loppers and the roots should be removed as much as possible. Revisit the roots to cut back any regrowth.

Himalayan blackberry should be removed the same way as the sweet-briar rose: cut back, and then dug out. Note that these plants are sun-loving and grow most prolifically in areas that would normally contain a tree canopy dense enough to prevent their establishment. Consider planting trees to restore the canopy as a long-term management strategy.

English hawthorn should be dug up. Like English holly, this species will re-sprout from roots and is much easier to manage when it is a young seedling. Established trees can be girdled or treated with a systemic herbicide using a cut-stump method.

Resources:

EFloraBC

Invasive Species Council of BC

Habitat Acquisition Trust

Plants of Coastal British Columbia, Pojar and Mackinnon


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