Seed morphology and allelopathy of invasive Praxelis clematidea


  • Suphannika INTANON Naresuan University, Department of Agricultural Science, Phitsanulok 65000 (TH)
  • Buntoon WIENGMOON Naresuan University, Department of Physics, Faculty of Science, Phitsanulok 65000 (TH)
  • Carol A. MALLORY-SMITH Oregon State University, Department of Crop and Soil Science, Oregon 97330 (US)



germination; invasive plant; morphology; planting depth; praxelis; temperature


Praxelis [Praxelis clematidea (Griseb.) R.M.King & H.Rob.] is an invasive species that infests many agricultural systems globally, such as orchards, rubber plantations, and other economic crops. The purpose of this research was to study seed morphology, germination factors, and allelopathy of aboveground parts of P. clematidea. P. clematidea seeds are small, light, and possess pappi that allow them to be dispersed easily by wind or animals. Among four P. clematidea populations collected from different provinces in Thailand, the size of P. clematidea seeds ranged from 2.6 to 3.2 mm in length, 0.6 to 0.7 mm in width, and were 0.4 mm in thickness. The weight of P. clematidea seeds ranged from 0.13 to 0.21 mg. P. clematidea had about 44 to 48 seeds per head. Seeds germinated over a temperature range of 20 to 30 °C while high (45 °C) and low (10 °C) temperatures reduced germination. Maximum germination occurred when seeds were planted on the soil surface. No seedlings germinated when seeds were planted at a depth more than 1 cm. P. clematidea extracts from aerial plant parts at concentrations of 25 and 50% inhibited seedling growth of hairy beggarticks (Bidens pilosa L.). Basic knowledge of the seed biology of P. clematidea and allelochemicals can help in understanding the invasiveness and in developing management strategies for this weed.


Abbott J, White CL, Davis S (2008). Praxelis clematidea (Asteraceae), a genus and species new for the flora of North America. Journal of the Botanical Research Institute of Texas 2:621-626.

Anantanamanee Y, Maneechote C, Sathuwijarn S, Chaokongchak S (2013). Biology and ecology of praxelis (Praxelis clematidea R.M.King & H.Rob.) (in Thai). Retrieved 2016 January 28 from

Callaway RM, Ridenour WM (2004). Novel weapons: invasive success and the evolution of increased competitive ability. Frontiers in Ecology and the Environment 2:436-443.

Calosi JC, Cavers PB, Bough MA (1986). Dormancy and survival in buried seeds of proso millet (Panicum miliaceum). Canadian Journal of Botany 66:161-168.

Chen GQ, Guo SL, Huang QS (2009). Invasiveness evaluation of fireweed (Crassocephalum crepidioides) based on its seed germination features. Weed Biology and Management 9:123-128.

Cheng F, Cheng Z (2015). Research progress on the use of plant allelopathy in agriculture and the physiological and ecological mechanisms of allelopathy. Frontiers in Plant Science 6:1-16.

Chon SU, Nelson CJ (2010). Allelopathy in Compositae plants. A review. Agronomy for Sustainable Development 30:349-358.

Christ A, Ritter M (2019). A taxonomic study of Praxelinae (Asteraceae-Eupatorieae) in Rio Grande do Sul, Brazil. Phytotaxa 393:141-197.

Corlett RT, Shaw JC (1995). Praxelis clematidea: yesterday South America, today Hong Kong, tomorrow the world? Memoirs of the Hong Kong Natural History Society 20:235-236.

CRC Weed Management (2003). Weed management guide: Praxelis-Praxelis clematidea. Retrieved 2016 December 7 from

Falcão HS, Maia GLA, Bonamin F, Kushima H, Moraes TM, Lima CAH, … Batista LM (2013). Gastroprotective mechanisms of the chloroform and ethyl acetate phases of Praxelis clematidea (Griseb.) R.M. King & H.Robinson (Asteraceae). Journal of Natural Medicines 67:480-491.

Gardner AG, Williges KA (2015). Praxelis clematidea (Asteraceae): a new plant invader of Florida. Southeastern Naturalist 14:N21-N27.

Gniazdowska A, Bogatek R (2005). Allelopathic interactions between plants. Multi-site action of allelochemicals. Acta Physiologiae Plantarum 27:395-407.

Groenewegen T, Duistermaat H, van Valkenburg JLCH, Boer E (2017). Seeds of invasive plants. Retrieved 2019 July 15 from

Hierro JL, Callaway RM (2003). Allelopathy and exotic plant invasion. Plant and Soil 256:29-39.

Holland A (2006). Praxelis (Praxelis clematidea R.M.King & H.Rob). Weed Spotters Newsletter Autumn 3:5-6.

Inderjit, Keating KI (1999). Allelopathy: principles, procedures, processes, and promises for biological control. In: Sparks DL (Ed). Advances in Agronomy. Academic Press, New York pp 141-231.

ISTA (2016). International rules for seed testing. The International Seed Testing Association, Zurich, Switzerland.

Intanon S, Reed RL, Stevens JF, Hulting AG, Mallory-Smith CA (2014). Identification and phytotoxicity of a new glucosinolate breakdown product from meadowfoam (Limnanthes alba) seed meal. Journal of Agricultural and Food Chemistry 62:7423-7429.

King RM, Robinson H (1987). The genera of the Eupatorieae (Asteraceae). Monographs in Systematic Botany Vol. 22. Missouri Botanical Garden Press, St. Louis, USA.

Lamsal A, Devkota MP, Shrestha DS, Joshi S, Shrestha A (2019). Seed germination ecology of Ageratum houstonianum: A major invasive weed in Nepal. PLoS One 14:1-14.

Lu P, Sang W, Ma K (2006). Effects of environmental factors on germination and emergence of crofton weed (Eupatorium adenophorum). Weed Science 54:452-457.

Maia GLA, Falcão-Silva VS, Aquino PGV, Araújo-Júnior JX, Tavares JF, Silva MS, … Barbosa-Filho JM (2011). Flavonoids from Praxelis clematidea R.M. King and Robinson modulate bacterial drug resistance. Molecules 16:4828-4835.

Meyer SE, Carlson SL (2001). Achene mass variation in Ericameria nauseosus (Asteraceae) in relation to dispersal ability and seedling fitness. Functional Ecology 15:274-281.

Miller DA (1996). Allelopathy in forage crop systems. Agronomy Journal 88:854-859.

Moles AT, Ackerly DD, Webb CO, Tweddle JC, Dickie JB, Westoby M (2005). A brief history of seed size. Science 307:576-580.

Monaco TJ, Weller SC, Ashton FM (2002). Weed science: Principles and practices. Jon Wiley & Sons (4th ed), NewYork.

Omami EN, Haigh AM, Medd RW, Nicol HI (1999). Changes in germinability, dormancy, and viability of Amaranthus retroflexus as affected by depth and duration of burial. Weed Research 39:345-354.

Patsai S (2011). Allelopathic effect of Praxelis clematidea (Griseb.) R.M.King & H.Rob on germination and growth of some crops (in Thai). MSc Dissertation, Srinakharinwirot University, Bangkok, Thailand.

Peachey RE, Mallory-Smith C (2017). Influence of winter seed position and recovery date on hairy nightshade (Solanum sarrachoides) recruitment and seed germination, dormancy, and mortality. Weed Science 55:49-59.

Plant Protection Research and Development (2005). Guidebook: Weed management and herbicide application in 2004 (in Thai). The Agricultural Cooperative Federation of Thailand, Limited (1st ed), Bangkok, Thailand.

R Core Team (2018). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.

Rice EL (1984). Allelopathy. Academic Press (2nd ed), New York.

Sakai AK, Allendorf FW, Holt JS, Lodge DM, Molofsky J, Kimberly AW, … Weller SG (2001). The population biology of invasive species. Annual Review of Ecology and Systematics 32:305-332.

TH-BIF (2018). Office of Environmental Policy and Planning, Ministry of Science, Technology and Environment of the Government of Thailand: Thailand Biodiversity Information Facility. Retrieved 2019 February 22 from

Thepphakhun T, Intanon S (2016). Allelopathy effect of Praxelis clematidea extract on seed germination and growth of leaf mustard and rice (in Thai). In: Proceedings of the 14th Kaset Naresuan Conference, Faculty of Agricultural Resources and Environment, Naresuan University, Phitsanulok, Thailand pp 171-176.

TMD (2018). Thai Meteorological Department. Retrieved 2018 March 15 from

USDA (2014). Weed risk assessment for Praxelis clematidea R.M.King & H.Rob (Asteraceae)-Praxelis. Retrieved 2016 May 22 from

Vanijajiva O (2014). Effect of ecological factors on seed germination of alien weed Tridax procumbens (Asteraceae). Journal of Agriculture and Ecology Research 1:30-39.

Veldkamp JF (1999). Eupatorium catarium, a new name for Eupatorium clematideum Griseb. non Sch.Bip (Compositae), a South American species naturalized and spreading in SE Asia and Queensland, Australia. Gardens' Bulletin Singapore 51:119-124.

Vitousek PM, D'Antonio CM, Loope LL, Westbrooks R (1996). Biological invasions as global environmental change. American Scientist 84:218-228.

Wang ZH, Christie P, Chen QB, Liu XX, Xie LL, Bai CJ, Li XL (2006). Allelopathic potential and chemical constituents of volatile oil from Praxelis clematidea. Allelopathy Journal 18:225-235.

Waterhouse B, McFadyen R, Holland A, Thorp J (2003). Weed management guide: Praxelis-

Praxelis clematidea. CRC Weed Management. Retrieved 2018 June 15 from

Woolley JT, Stoller EW (1978). Light penetration and light-induced seed germination in soil. Plant Physiology 61:597-600.

Yuan X, Wen B (2018). Seed germination response to high temperature and water stress in three invasive Asteraceae weeds from Xishuangbanna, SW China. PLoS One 13:1-16.




How to Cite

INTANON, S., WIENGMOON, B., & MALLORY-SMITH, C. A. (2020). Seed morphology and allelopathy of invasive Praxelis clematidea. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 48(1), 261–272.



Research Articles
DOI: 10.15835/nbha48111831