Learning about Ligules

I’m out on the west coast of Vancouver Island this weekend finding out more about Parks Canada’s dune restoration program in Pacific Rim National Park Reserve.

European Beachgrass (Ammophila arenaria)
European Beachgrass (Ammophila arenaria) creates a wall at the edge of the dunes that prevents sand movement.

Sand dunes up and down the west coast of North America are being choked with introduced grasses, in particular European Beachgrass (Ammophila arenaria) and American Beachgrass (Ammophila breviligulata). These species do a very good job of preventing sand movement (which is why they were introduced in the first place). Unfortunately, most of the native species of plants that can be found in coastal dune ecosystems depend, and even thrive in conditions that are dynamic and changing with a lot of sand movement.

American Beachgrass (Ammophila breviligulata)
American Beachgrass (Ammophila breviligulata) forms dense clumps in sand dunes.

Examine the Ligules

Grasses are fairly challenging to identify but with a little effort both of these “awful ammophilas” can be separated from the native Dune Grass (Elymus mollis). To do so, one must learn a little about ligules.

European Beachgrass (Ammophila arenaria) ligules
The ligules of European Beachgrass (Ammophila arenaria) look a little like rabbit ears.

The ligule is a small membranous flap that occurs where the sheath of the blades of grass joins the stem of the plant. In the case of European Beachgrass, the ligule is very pronounced, looking a little like a pair of up-right ears. In contrast, American Beachgrass has a very blunt ligule with some fringing.

American Beachgrass (Ammophila breviligulata) ligule
The ligules of American Beachgrass (Ammophila brevilligulata) are blunt and sometimes fringed.

Blade Width Differences

Visually there are some other differences as well. European Beachgrass tends to have a thinner leaf (2-4 mm wide) than American Beachgrass (4 – 8 mm wide). In addition, European Beachgrass has a bit of a papery sheath appearance to the base of the stalk of grass while American Beachgrass usually has reddish markings at the base of the leaves.

Overall Visual Differences

All of these characteristics require some close examination of the grass itself. A superficial look at the wall of grass marking the top of the beach and the beginning of the dunes might lead one to assume that it is all European Beachgrass. While European Beachgrass is the dominant species, American Beachgrass grows here as well. The native Dune Grass looks quite different in that its leaves are a bluish green in colour and fairly wide (6 – 15 mm wide). Dune Grass has short ligules as well so some care must be taken to separate it from the American Beachgrass since there is some overlap in leaf width. Dune Grass tends to grow in more isolated patches and doesn’t form the thick networks of vegetation that is typical with both species of Ammophila.

Three Grasses
All three grasses are shown here – left and right foreground is Dune Grass (Elymus mollis), middle foreground is American Beachgrass (A. breviligulata), and European Beachgrass (A. arenaria) in the background.

Working to Remove the Introduced Grass

This winter Parks Canada is working to remove substantial sections of Ammophila from the edge of the dunes to encourage sand movement from the beach deeper into the dunes.

In previous years, small scale removal of beachgrass by hand and excavator has resulted in dramatic changes in plant communities in the dunes, restoring the natural sand dune ecosystem. An ongoing larger scale project involving two backhoes began this fall. Large sections of beachgrass have been removed and while it looks a little messy right now, winter storms, wind and waves will finish the work by redistributing the sand and reshaping the dunes. It will be interesting to see the results in the spring!

As you’re visiting the beaches and dunes on the west coast of British Columbia and the United States look for these two species of grass. They are invasive and can radically change a sand dune ecosystem. Check with your local national, provincial, or state parks to find out what is being done to restore the dunes to their natural state.

Further Reading

More botanical delights can be found at Berry Go Round, this month hosted by Bora over at Blog Around the Clock.