Drive down any Ontario highways in early July, and it is hard not to notice the bright yellow blooms of birdsfoot trefoil (Lotus corniculatus).
In Sarnia, our prettiest birdsfoot trefoil crop can be found in two not-yet-developed patches of grass south of the Walmart parking lot, next to LCBO.
Birdsfoot trefoil is so named because once the flowers fall, the remaining seed pods look like birds’ feet. The perennial plant has sulphur yellow blooms rising above small green foliage with tough, wiry stems.
Birdsfoot trefoil is listed as an invasive species in many jurisdictions, primarily south of the border, where it invades grasslands home to many native plants. In Ontario, it gets mixed reviews. Trefoil has several benefits, and has often been used as green manure cover crop in agriculture, plowed under to add valuable soil nutrients.
Trefoil was introduced to North America from Europe with good intentions. It served as nutrient-rich forage for animals, and, as a member of the pea family, hosted bacteria that fixed nitrogen, boosting soil fertility.
Nature lovers appreciate trefoil for their bright yellow blooms, which often attract pollen-seeking bees.
On the other hand, trefoil grows where little else grows, and once established, can inhibit valuable native plants. Though not as invasive as phragmites, purple loosestrife, or Queen Ann’s lace, we would do well to keep an eye on trefoil’s aggressive path.
Trefoil can grow in the poorest soils because its roots, which are difficult to pull, go deep in search of moisture. It needs no fertilizer because it creates its own nitrogen. Trefoil is often the first weed to grow at the edge of a gravel road.
Trefoil can be a lawn weed, particularly in poorly tended, underfertilized lawns. It likes drought and sunshine, but can survive in damp soil. Since it needs sun, it’s not found in forests.
Along the highway, birdsfoot trefoil enjoys the company of several other non-native weeds. In the past, Crown vetch was planted by the Department of Highways as a soil stabilizer to prevent erosion on slopes. Knapweed, listed as an invasive species, has pale purple flowers and grows in neglected areas with poor soil.
Ontario’s worst offender is phragmites, a tall grass-like weed that grows in ditches and wherever it can find moisture. Like a bulldozer, it expands in neglected areas with no regard for other plants in its path.
Once established, roadside invasive weeds are hard to get rid of. Controlled burning will set them back, but not eliminate them. Herbicides can be effective, but there is general reluctance to apply weed killer unless necessary.
Planting wildflowers in hopes they’ll outperform non-native plants has been largely unsuccessful because native plants prefer native environments.
- The greenhouse pot has become an ecological marvel
- Recycle your plastic flowerpots, trays at any Meijer Garden Center
- Video: Brazen theft at popular garden center in St. Louis County
- Opportunity Center at ALCC celebrates new Sharing Garden site
- Weekend picks: Angela Two Stars speaks about her poetic piece at the center of the Sculpture Garden