Noel Pavolvic 


Top: The yellow 
orange fruits of 
Asiatic bittersweet (C. 
orbiculatus). 
Bottom: The extensive 
root sprouting of Asiatic 
bittersweet, the orange 
resprouts as compared 
to the original stems that 
are painted pink. 
Lianas — continued trom page 1 
the seeds of the hybrids were sterile (Zaya et 
al. 2015). This explained why hybrids were not 
pervasive where the populations met, but not why 
American bittersweet is declining. More detailed 
studies, however, revealed that Asian plants 
produce much more pollen than their American 
cousins and that its pollen was more successful at 
crossing with American stigmas. Thus, American 
bittersweet gets genetically swamped by Asiatic 
pollen resulting in local extirpation. Asiatic 
“| bittersweet produces 200 times more male 
flowers and 95 times more female flowers 
than American bittersweet. This interference 
extends beyond 300 feet, so to protect 
American bittersweet, Asiatic bittersweet has 
to be removed for a considerable distance 
(Zaya et al. 2021). 
Since fire is a natural process in prairies 
and savannas, we needed 
to understand how Asiatic 
bittersweet responds. More 
bad news: the data showed 
that burning initiated root 
suckering and could more 
than double the density 
of stems (Pavlovic et al. 
2016). With extensive 
horizontal roots, Asiatic 
bittersweet can spread 
quite broadly and make it 
difficult to eradicate. We 
gave up excavating one 
root after digging horizontally for over 15 feet. On 
a promising note, in one experiment we followed 
the carbohydrates (think starches) stored in the 
roots of the plants over the seasons. These 
root carbohydrates are stored over the growing 
season and depleted in the spring when the 
carbohydrates provide energy for new growth after 
breaking dormancy. Cutting the plants in early July 
immediately after the spring growth spurt, resulted 
in a 50% reduction in root carbohydrates from their 
normal levels. While we have not yet done the 
experiment, this pattern suggests that herbiciding 
Asiatic bittersweet might be more successful in late 
summer and early fall after cutting because they 
are much weaker than normal. 
In 2010, | gave a talk in St. Paul, Minnesota 
about our bittersweet research. A few years later 
the Minnesota Extension Service got a law passed 
2 « Indiana Native Plant Society « Summer 2021 

by the state legislature that banned the sale and 
transport of Asiatic bittersweet within the state. 
Subsequently, | happily saw American bittersweet 
growing in a Minnesota hill prairie free of invasive 
pollen. Some good has come from our research 
regarding this bittersweet tale of two lianas. If 
more states along the west side of the Mississippi 
River ban the sale and transport of Asiatic 
bittersweet, the American bittersweet may be able 
to range more freely across the plains. 
References 
Del Tredici, P. 2014. Untangling the twisted tale of 
oriental bittersweet. Arnoldia (Jamaica Plain) 71:2-18. 
Leicht-Young, S.A., N.B. Pavlovic & R. Grundel. 2013. 
Susceptibility of eastern US habitats to invasion of 
Celastrus orbiculatus (oriental bittersweet) following 
fire. Forest Ecology and Management 302:85-96. 
Leicht-Young, S.A., N.B. Pavlovic, R. Grundel & K. 
Frohnapple. 2007. Distinguishing native (Celastrus 
scandens L.) and invasive (C. orbiculatus 
Thunb.) bittersweet species using morphological 
characteristics. Journal of the Torrey Botanical 
Society 134:441-450. 
Pavlovic, N.B., S.A. Leicht-Young & R. Grundel. 
2016. Oriental bittersweet (Celastrus orbiculatus): 
spreading by fire. Forest Ecology and Management 
364:183-194. 
USGS. 2021. American and oriental bittersweet 
identification. http:/www.co.becker.mn.us/dept/ 
soil_water/PDFs/Wweeds/Oriental_Bittersweet. pdf 
(accessed 21 April 2021) 
Will, G.F. 2014. A nice little place on the north side. 
Crown Architype. 
Zaya, D.N., S.A. Leicht-Young, N.B. Pavlovic & M.V. 
Ashley. 2021. Heterospecific pollination by an 
invasive congener threatens the native American 
bittersweet, Celastrus scandens. PLoS One 
16:e0248635. 
Zaya, D.N., SA. Leicht-Young, N.B. Pavlovic, 
K.S. Feldheim & M.S. Ashley. 2015. Genetic 
characterization of invasion, hybridization, and 
native species decline in Ce/astrus. Biological 
Invasions 17:2975-2988. 
Zaya, D.N., S.A. Leicht-Young, N.B. Pavlovic, C.S. 
Hetrea & M. V. Ashley. 2017. Mislabeling of an 
invasive vine (Celastrus orbiculatus) as a native 
congener (C. scandens) in horticulture. Invasive 
Plant Science and Management 10:313-321. 
Noel B. Pavlovic, a member of the Northern 
Chapter of INPS, is an incorrigible botanist and 
a research plant ecologist working at the US 
Geological Survey, Lake Michigan Ecological 
Research Station in the Indiana Dunes 
National Park. 

