This post deals primarily with some of the lesser known, but problematic non-native species in a terrestrial environment. Others, especially some that are more well known and problematic in wetland environments will be discussed in a future post.
One of the less problematic terrestrial ones is Moth Mullein (Verbascum blattaria). It is not common anywhere that I have seen it here in southwestern Ontario, and is rather attractive.
Closely related to this is one that is probably more familiar to most readers: Common Mullein (Verbascum thapsus). It is definitely more problematic in woodland edges and disturbed sites.
Multiflora Rose (Rosa multiflora) is common place, even in prime natural areas such as Rondeau Provincial Park where it has come to dominate certain areas.
Globe Thistle (Echinops sphaerocephalus) starts off looking a bit like a more common thistle, but soon appears with its characteristic globe shaped flower head. It is abundant along the rail corridor.
|Common Goat's Beard|
|Everlasting Pea (Lathyrus latifolius)|
|Butter-and-eggs (Linaria vulgaris)|
|Rough-fruited Cinquefoil (Potentilla recta)|
|Teasel (Dipsacum sylvestris)|
This next image shows the exotic Cabbage White butterfly (Pieris rapae) on the exotic Catnip (Nepeta cataria), while the image that follows shows a male and a female Cabbage White on Viper's Bugloss (Echinocystis lobata), also exotic.
Then we get into some nastier, aggressive species. For example, White Mulberry (Morus alba). It is common along hedgerows, roadsides, urban and rural lots, railroad corridors, river valleys even some high quality natural woodlands. The dilemma is that the fruit is tasty to birds, racoons even humans. If you want to find birds in mid summer, find a few White Mulberry trees with abundant fruit as shown in the next image. There you will also find various fruit-eating birds, including American Robins, Gray Catbirds, Brown Thrashers, Cedar Waxwings and the like. However after the birds gorge themselves on these tasty berries, they leave and being members of the group of birds known as Passerines (perching birds), they perch on wires, fences, tree branches. And as the saying goes, what goes in must come out.....so when their digestive processes have completed the job, the seeds are pooped out wherever they happen to be sitting, sometimes several kilometres from where they originated. After a few decades, White Mulberry is all over the landscape.
Another problematic plant species is White Sweet-Clover (Melilotus alba). It is a biennial, meaning that it takes two years to get to the seed-producing stage. Disturbed areas and even good quality natural areas such as tallgrass prairies, can have this species in abundance.
It can be difficult to find in an area one year as the first year's vegetative growth is under way. The following year it is super evident. It is a prolific seed producer, and the seed can last for years in the seed bank, so it is very hard to control. It also has a cousin, known as Yellow Sweet-Clover (Melilotus officinalis).
|Abundant White Sweet-Clover|
Another abundant but perennial species is Spotted Knapweed (Centaurea maculosa).
|Spotted Knapweed in abundance|
This brings me to what I consider one of the worst of the worst in terrestrial areas: Dog-strangling Vine, also known as Pale Swallow-wort (Vincetoxicum rossicum).
It is a perennial, a fast-growing vine and a prolific seed producer. It has seeds somewhat similar to milkweed, which are transported by air, so it can spread quickly. It also spreads very easily if even a small piece of a stem is transported to a potential site elsewhere.
There are many more exotic species present throughout southern Ontario and elsewhere. In fact on average even in a good quality natural area, the non-native plant species make up about 20-25% of the total list, but are often much greater in overall abundance. In highly disturbed sites such as railroad corridors, they can make up an even greater per cent of the plant list. They are here in abundance because of the great levels of alteration of the original landscape, courtesy of you and I and our predecessors. But that will be the topic of a future post.