Some species of plants may look very similar to one another, but only be distantly related! And sometimes, two closely-related plants look like twins but behave very differently (do you have a headache yet?)
For the most part, invasive species are fairly easily differentiated from our native species. They tend to be larger, showier, and brighter than our native species. It gets more difficult to tell them apart when an invasive species has a native lookalike, though! How do you know which one is invasive and which is native?
Here’s a list of a few of those pairs of lookalikes in the Sea to Sky and how you can tell them apart.
Bull Thistle vs. Wavy Leaf Thistle
Both have very similar flowers, leaves, stems, and taproots. Bull Thistle, however, is generally quite a bit larger than Wavy Leaf Thistle.
Bull Thistle will grow groups of flowers, while Wavy Leaf Thistle grows solitary flowers. Wavy Leaf Thistle has woolly hairs on both sides of the leaves, while Bull Thistle only has them on the undersides of leaves with spiny hairs on the tops.
Bull Thistle grows taller, up to 2 m tall, compared to Wavy Leaf Thistle’s 0.3 – 1.2m. Bull Thistle’s spines are also much longer: 5 – 10 mm long, compared to Wavy Leaf Thistle’s 1 – 5 mm long spines.
Flat Pea vs. Marsh Peavine
These two species are actually part of the same genus, meaning that they’re very closely related. They may be cousins but they are different sizes: Marsh Peavine grows to be 30 – 100 cm long, compared to Flat Pea which can be 60 – 200 cm long.
Flat Pea’s leaves are quite different from those of Marsh Peavine. Flat Pea’s leaves are divided into two long, pointed leaflets. Marsh Peavine has leaves that are divided into 4 to 8 smaller, more oval leaflets.
Both plants may produce pea-like flowers, but that’s where the commonalities end. On the one hand, Flat Pea produces groups 4 – 9 pink flowers (though they may also be red or white); on the other hand, Marsh Peavine flowers occur in groups of 2-8 and range from blue to pink. Note that at maturity, both flowers will produce pea-like pods that contain seeds.
Giant Hogweed vs. Cow Parsnip
Again, these two plants are part of the same genus and are very closely related. In fact, Giant Hogweed is sometimes even called Giant Cow Parsnip! Since they’re so closely related, the main difference between the two species is their size.
Giant Hogweed is much taller than Cow Parsnip. It can be up to 5 m tall and can have stems as thick as 10 cm wide. Cow Parsnip, on the other hand, generally grows to be 1 – 3 m tall. Giant Hogweed has leaves up to 1.5 m wide and 3 m long, while Cow Parsnip has leaves 60 – 75cm wide and 10 – 40cm long.
Due to how closely related they are, both of these species produce toxic sap that can cause severe burns when exposed to sunlight. If you want to read more about these two, we have a whole post dedicated to them here!
Blueweed vs. Arctic Lupine
These two species look very similar at a glance. Both have tall spikes covered in bright blue-purple flowers and grow to about the same height. However, their flowers and leaves are quite distinct from one another.
Blueweed has flowers on the upper side of arched stems growing off the main floral spike. The flowers are 5-lobed, radially symmetrical, and funnel-shaped. Arctic Lupine’s flowers are pea-shaped, with an upper and lower lip and typically with some white patterning. These flowers are attached to the main floral spike, arranged roughly in whorls around it.
Blueweed has lance-shaped leaves that grow from the main stem. The leaves are covered in stiff, bristly hairs that can irritate the skin. Arctic Lupine has unique leaves that grow at the end of long stems. The leaves are palmate, comprised of between 6 and 10 smaller leaflets (they look like little hands to us!). While Arctic Lupine’s leaves also have hairs, they are mainly located on the undersides of the leaves and are much less bristly.
Orange Hawkweed vs. Orange Agoseris
At a glance, both of these plants look like bright orange dandelions. That’s not their only similarity: Orange Hawkweed is covered in long, bristly hairs and oozes a milky sap if broken. Orange Agoseris is also hairy, although the hairs are shorter and mostly found on the stem. Like Orange Hawkweed, Orange Agoseris oozes a milky sap when a stem is broken.
Orange Hawkweed flowers usually grow in clusters at the top of the stem, while Orange Agoseris only has one flower per stem. The stems of both plants are generally 10 – 60cm tall.
Orange Hawkweed has leaves that are oval-shaped and covered with hairs. Orange Agoseris leaves are much pointier and have hardly any hairs.
When you know what you’re looking for, it’s fairly easy to make sure that you’re looking at the right species. Check out the videos below for some more pairs of Native-Invasive lookalikes! This page contains more helpful information you might enjoy on plant identification.
Make sure to report any sightings of the invasive plants you see on this list to help us understand their current distribution in the Sea to Sky!
More Native vs. Invasive Lookalikes:
English Holly vs. Oregon Grape
Knotweed vs. Ocean Spray
Trailing Blackberry vs. Himalayan Blackberry