2 January 2010

How do I tell the difference between the native and invasive...

1. ...Phragmites?

See "Phragmites: Common Reed - Morphological differences between native and introduced genotypes" at Cornell's Biological Control Program

2. ...native American bittersweet vine Celastrus scandens and the invasive exotic oriental bittersweet C. orbiculatus?

"Using fruit and leaf characters, the two species can be discriminated from each other. However, certain traits are more reliable for correct identification than others. Classically, the position of the fruit and flowers on the stems has been cited as the most definitive means of discriminating between the species. Oriental bittersweet has fruit and flowers located in the leaf axils along the length of the stem. American bittersweet, however, only has fruit and flowers in terminal clusters. There is also a difference in the color of the capsules surrounding the ripened fruit in the fall. Oriental bittersweet has yellow capsules, while those of American bittersweet are orange. Another difference in color is the pollen color of the male flowers. The pollen of oriental bittersweet is white while that of American bittersweet is yellow..." - American and Oriental Bittersweet Identification - the US Geological Service's Great Lakes Centre
Note: along a couple southwestern Ontario roadsides, I found both species side by side + the hybrid species of the two. So I couldn't even seed collect from the native species, because of the possibility the flowers had been cross-pollinated / its seeds would be hybrids.

3. ...native eastern Wahoo
Euonymus atropurpurea vs. the invasive exotic winged burning bush E. alata, climbing euonymus E. fortunei and spindle tree E. europaea?

Unfortunately, around here, it's probably the exotic -- I haven't stumbled by the real thing yet -- still to be sure (and you have to be because there are a few out there + some native plant nurseries sell them = some one's planting them some where) the best native vs invasive
euonymus ID advice I've found is on page 123 of “Growing Trees from Seed - A Practical Guide to Growing Native Trees, Vines and Shrubs" by Henry Kock with Paul Aird, John Ambrose and Gerald Waldron:
European spindle tree E. europaea [exotic]: the identification of this close relative of E. atropurpurea can only be made with certainty at flowering time. The European species has greenish white flowers in late May as compared to the maroon flowers (in June) of the native wahoo. The European spindle tree holds its leaves much longer into the fall, and the twigs tend to be thicker and more rigid than wahoo. However, due to variability in both species, the two are occasionally so similar vegetatively (including the root sprouting) that without knowledge of the flowers, the nearly identical fruit should be left alone – or the flower colour should be verified in late May.

Winged burning bush E. alata [exotic]: A dense, outward-arching bush originating in Japan. It has small orange fruits on short stems that persist into the winter. Twigs on this species are prominently four winged, a characteristic that is more diminutive on a more compact-growing horticultural cultivar but still gives this species a distinctly square-stemmed appearance.

[Besides these] two 'ornamental' deciduous shrubs that ...have become naturalized (extensively in many places) in close proximity to older settlements and parks ...garden escapees of the evergreen-leaved Euonymus fortunei [exotic climbing euonymus aka wintercreeper] are also beginning to find their way into the wild."


How It Grows said...

The phragmities comparison is very helpful! Thanks

native plant girl said...

what can i say except, i know i put-my-hands-in-the-air for the good weed-folks publishing out of Cornell :)

and happy new year!

Felicity said...

I have been meaning to say a very big thank you for your blog and all the excellent links for a few months now ( since I discovered you) but because I don't have an online name and can't seem to think of one, I have been putting it off. Now however the link to the article on bittersweet has forced me into action. I am going to use my real name!

I live in Toronto condo but have a summer retreat in Norfolk Co. where I have a bittersweet I bought many years ago before the interest in native plants was as widespread as it is today. Although I was told at the time it was "native" I have been skeptical since I discovered how similar they are and because I have various other purchases from the early days of my garden that though sold as "native"turned out to be similar exotic species. My plants have never flowered (too shady I suppose? or not mature enough?) though they have been growing for ten years if not longer) Now with the leaf characteristics described in the article I should have a shot at identification. THANKS!

If you haven't got tired of reading this by now I would just like to say that I value the information you pass on and know it to be of the highest quality because I know from my own experience that many of the things you say are accurate e.g. I too am a big fan of both Henry Kock and Mary Gartshore. So I look forward to exploring books and web sites I am not familiar with, eg the Crosby book and the Aliens list serve.
Now I will shut up.

Steve S said...

I bought one from Mary G once and grew it to see if it was native and it wasn't. She was shocked and stopped growing them for a while.

Always be careful with some of these tricky species. Asian bittersweet is one of the new invasives that is poised to explode across Ontario.

native plant girl said...

Felicity :)

THANK YOU sincerely for the best comment ever! :)

BTW: if you contact by email nativeplantgirl[at]sympatico.ca i have cool free map of green spaces in Norfolk I'd like to send to you!

thanks again!!

native plant girl said...


hi :)

poised and exploding... saw it mixed in w/ the natives even on walpole this past fall. here's what's vexxing me: if they're hybridizing right on the vine, how do seed collectors know their not picking hybridized seeds from a american bittersweet? how do growers isolate/prevent their american bitersweets from being hybridized? What i mean is: how can i know that any seed source is pure?

might help if knew its pollinators and their range? Do you think it's insects, or birds? If it's birds... wow - there are migratory birds who over a lot of area dining on both in the fall.

Steve S said...

I haven't heard of hybrids being formed, just the invasive being more common. Not sure what to do. I think we'd need some university botany types to look into hybridization before we say it's happening and scare everyone.

native plant girl said...


Thank you again for your "peer review" caution. i need it. i'm definitely not a botanist.

here's what i'm going from:

"Interspecific hybridation betwween the native bitersweet, Celestrus scanden, and the introduced invasive species, C. orbiculatus" see the abstract at http://www.jstor.org/pss/3878246


"Oriental bittersweet has been shown to hybridize with the relatively rare American bittersweet (Celastrus scandens L.). Hybridization may lead to the loss of American bittersweet's genetic identity through introgression." from: http://www.se-eppc.org/manual/bittersweet.html


C. scandens ...C. orbiculatus ...The two species may be capable of hybridizing and since the native is relatively rare it is possible that its distinct genetic identity is threatened." from: http://www.invasive.org/gist/esadocs/celaorbi.html


"Researchers at the Connecticut College Arboretum and the College's Botany and Zoology Departments (Dreyer, Clement, Wheeler, etc.) Future research will probably continue to examine the comparative species biology of C. scandens vs. C. orbiculatus. No other active research programs are known. Management Research Needs:
Research in species biology is needed in the following areas: pollination ecology; extent of natural hybridization with C. scandens; mechanisms of seed dispersal; annual vegetative growth rates; mechanisms of rootsucker induction; possible allelopathic effects on other species; seed bank dynamics."
Research is also needed to define the current range of C. orbiculatus and to monitor subsequent spread. Work on biological control methods is apparently completely lacking. Langdon (1993) located an ornamental planting of C. orbiculatus in north Georgia that was losing vigor due to an infestation of Euonymus scale (Unaspi euomyi) and suggests this lead should be followed. The little published on chemical and mechanical control indicates further work in these areas would also be fruitful."

native plant girl said...

steve couple more:

Kaufman and Kaufman's "Invasive Plants - Guide to Identification and the Impacts and Control of common North American Species": "Oriental Bittersweet can hybridize with the relatively rare American Bittersweet, potentially threatening the genetic identity of American bitersweet" but they're citing the 1st article i mentioned ("Interspecific hybridation between the native bitersweet, Celestrus scanden, and the introduced invasive species, C. orbiculatus" see the abstract at http://www.jstor.org/pss/3878246)

From page 104 / the Celestrus section in "Growing Trees from Seed by Henry Kock et al "the exotic will hybridize with our native species".

all this comes back to what i was saying about how to ensure pure seed source, AND it's my hunch about why Mary G was "shocked" to see what came up.

Steve S said...

Makes sense then. Something to look for. I'm always extremely cautious about quoting people about research that can't be verified easily by average people though.

Research can be too specific or just done wrong and lead them to make conclusions that don't work in the real world, or may be proven wrong by a better study in future, but in the meantime we are left in limbo.

There are so many of what I call 'Grey Areas' in this field that warning people to look out for things that are hard to deal with on a site level and that takes years of lab research to prove or confirm just induces them to give up and plant ornamentals, or say that restoration doesn't work so why bother trying. I get bothered with this on projects by big landscape architect firms sometimes.

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