Ageratum houstonianum Mill., Gard. Dict. ed. 8 1768. (Syn: Ageratum mexicanum Sweet; Ageratum wendlandii Bailly; Carelia houstoniana (Mill.) Kuntze ..);
flossflower, bluemink, blueweed, pussy foot, Mexican paintbrush ;
It (Ageratum houstonianum) has larger and robust plants and flowerheads with more florets than A.conyzoides.
In A conyzoides plants and phyllaries are not that densely hairy, and heads are smaller and more spreading
Thicker cordate leaves and longer hairs especially on involucre bracts are clearly seen in Ageratum houstonianum.
Ageratum L. genus is represented in India by two species- A. conyzoides and A.houstonianum.
These closely related pantropica weed species can be differentiated as follows:
Involucral bracts linear, sharply acute-acuminate, sparsely hairy; Corolla of the florets 1.5mm long, shorter than awned pappus scale…. A.conyzoides L.
Involucral bracts linear setaceous, densely hairy; Corolla of the florets 2.5mm long, as long as or longer than awned pappus … A.haustonianum Mill.
Ageratum houstonianum (flossflower, bluemink, blueweed, pussy foot, Mexican paintbrush) syn. Ageratum mexicanum Hort. is a cool-season annual plant often grown as bedding in gardens.
The plant grows to 0.3–1 m high, with ovate to triangular leaves 2–7 cm long, and blue flowers (sometimes white, pink, or purple). The flower heads are borne in dense corymbs. The ray flowers are threadlike, leading to the common name.
The plant is native to Central America and adjacent parts of Mexico, but has become an invasive weed in other areas.
Ageratum has evolved an ingenious method of protecting itself from insects; it produces a precocene compound which interferes with the normal function of the corpus allatum, the organ responsible for secreting juvenile hormone. This chemical triggers the next molting cycle to prematurely develop adult structures, and can render most insects sterile if ingested in large enough quantities. 
Ageratum houstonianum is toxic to grazing animals, causing liver lesions. It contains pyrrolizidine alkaloids.
A. houstonianum is prone to becoming a rampant environmental weed when grown outside of its natural range. It has become an invasive weed in the eastern USA, Australia, Europe, Africa, China, Japan and New Zealand.
(From Wikipedia on 9.6.13)
Asteraceae Fortnight Part 2-Discoid heads: Ageratum houstonianum Mill. from Delhi-GS4 : Attachments (3). 2 posts by 2 authors.
Ageratum houstonianum Mill.
Cultivated herb differing from A. conyzoides in more robust plants, thicker ovate-cordate leaves, larger purple-lilac heads with hairy involucre bracts.
Photographed from Delhi.
ASTERACEAE Fortnight Part 2-Discoid heads: Ageratum haustonianum from Uttarakhand_DSR_3 : Attachments (3). 2 posts by 2 authors.
Ageratum haustonianum Mill. is a widespread species in Pantnagar and more common than A.conyzoides.
It has larger and robust plants and flowerheads with more florets than A.conyzoides. The last picture shows both of these species together.
Yes … Very good photographs
Hooghly Today : Ageratum houstonianum Mill.: Attaching photographs of Ageratum houstonianum Mill., recorded today.
Asteraceae Fortnight Part 2-Discoid heads : 050613 ARK-00 : Ageratum houstonianum from Almora, Uttarakhand : Attachments (2). 1 post by 1 author.
Attached are pictures captured at Almora, Uttarakhand in November 2012
Asteraceae Fortnight Part 2-Discoid heads:: Ageratum houstonianum BRS 2 : Attachments (1). 3 posts by 2 authors.
Sharing the images of Ageratum houstonianum from Munnar Kerala.
Asteraceae Fortnight Part 2-Discoid Heads: Ageratum conyzoides from Kaithal- NS 03 : Attachments (6 + 5). 6 posts by 3 authors.
This common weed was shot from field margins near my village, both white and purple heads growing together…
I hope all the pics belong to Ageratum conyzoides L.
I have some doubts …, because A. houstonianum (cordate leaves and hairy involucre bracts) also sometimes is found as an escape.
Thanks sir for valuable inputs… I also do had doubts.. in fact, whatever Ageratum we find in our locality, quite widespread as a weed, is the same posted here, means A. houstonianum is far ahead in dispersal than A. conyzoides, which I have not yet found in our area.. of course that is common in hilly areas… attaching few more pics recorded day before yesterday, with this mail… assuming them to be Ageratum houstonianum…. please help to clear the doubts..
efi pages on Ageratum conyzoides & Ageratum houstonianum with keys.
Requesting ID of this plant – Mumbai :22072013 : ARK-03 : February 2013 : Attachments (1). 3 posts by 2 authors.
Requesting to please ID this plant captured at the Flower show Mumbai, in February 2013.
Identification of Asteraceae member requested AL1 : 4 posts by 4 authors. Attachments (1)
help me in the identification of this is a herb, about 1 m high, the heads are about 1-1.5 cm across; photographed at the banks of Chambal river, near Kota Rajasthan
Ageratum houstonianum, perhaps.
I agree with …, one my upload was identified by … KEY can be found in eFI page – /species/a—l/ar/asteraceae/ageratum/ageratum-houstonianum.
Ageratum houstonianum Mill. SN15March 06 : 1 post by 1 author. Attachments (3)
Ageratum houstonianum Mill, a frequent weed from Yercaud, Salem dt Tamilnadu
Kalatope id al190411a: 9 posts by 5 authors. Attachments (3)
Location Kalatope, Chamba
Altitude 1400 mts
Height 18 inches
I assume that was a slip of finger!!
Thanks … for pointing out. Yes I was to write Ageratum conyzoides
Is it not A. houstonianum?
efi page on Ageratum conyzoides & Ageratum houstonianum
Yes It is Ageratum houstonianum
Plant for ID-PC-01-01.10.2015 : 3 posts by 2 authors. Attachments (2)
please identify the plant in the picture. The snaps were taken on way to Uttarakhand.
Ageratum haustonianum to me.
Ageratum conyzoides L. (provisionally accepted name) : 4 posts by 2 authors. Attachments (10)
Location: Godawari, Nepal
Altitude: 5000 ft.
Date: 10 January 2017
Nepali Names : भेडा झार Bhedaa Jhaar / बोके घाँस Boke Ghaans / गनमने घाँस Ganamane Ghaans / गनाउने झार Ganaaune Jhaar / सेतो रावन्ने Seto Rawanne / गन्धे Gandhe
I think more closer to images at Ageratum houstonianum as per comparative images at Ageratum
Yes it looks similar to Ageratum haustonianum
Ageratum houstonianum Mill.
Ageratum houstonianum FOR VALIDATION :: Bhagamandala – Thalacauvery Road :: 22 FEB 2017 : 3 posts by 2 authors.
Bhagamandala – Thalacauvery Road Karnataka
Date: 22 FEB 2017 … Altitude range: ~ 907 – 1122 m (2976 – 3683 ft) asl
Ageratum ¿ houstonianum ? … (family: Asteraceae) … exotic, naturalized
I think close as per images at Ageratum houstonianum Mill.
Ageratum houstonianum /Ageratum conyzoides confirmation ? : 4 posts by 2 authors. Attachments (5)
Please help to confirm these Ageratum species
Are these two different species? Or are the both plants A.houstonianum as there are many colour variants of A.houstonianum
The plant with purple coloured inflorescence are as tall as 3 feet tall and present throughout the year while plants with white inflorescence are generally smaller about 1-2 feet only and are mainly seen in rainy and summer season.
Thanks, … If you check in efi site, may be your issues are resolved.
I have also checked previously but now again after checking sir I have found important image by …
Ageratum houstonianum (planted) :: Yercaud :: 25 JAN 18 : 2 posts by 2 authors. 3 images.
Yercaud … (literally, lake forest), Tamil Nadu
… planted ornamental … Date: January 25, 2018 … Altitude: about 1,623 m (5324 feet) asl
Ageratum houstonianum Mill. … (family: Asteraceae)
Ageratum for ID :: MAR2018 MK003 : 2 posts by 2 authors. Attachments (6)
Please help me identifying this herb; could this be Ageratum houstonianum?
Height: almost 1-2 feet
Habitat: exposed localities & near streams
Alt.: 350 m asl
Place: Jammu (outskirts, rural), J & K
Appears close as per
Thank you … For me also, the plant looks more like Ageratum houstonianum.
21022018PP1 : 7 posts by 4 authors. Attachments (1)
Location: Bombay Shola, Kodaikanal, Tamil Nadu
Altitude: 2100 m
Approx. height: 10 cm
Insertion of leaves: Alternate
Approx. size of middle leaves: 1 cm
Flower diameter and length: 0.5 × 0.5 cm
Is this Eupatorium? If so, which species?
Looks like Chromolaena odorata (L.) R.M.King & H.Rob.
Family : Asteraceae
I think closer to images at Ageratum houstonianum Mill. rather than those at Chromolaena odorata (L.) R.M.King & H.Rob.
I think it is Ageratum Connyzoid /Billy goatweed.
It is alien invasive species.
More clear pic of leaves will tell more clearly as flower of both A. Connyzoid and A. Haustonianum are similar, but leaves have differences.
Thanks, … It is Ageratum houstonianum Mill. only
Pl. see Ageratum houstonianum /Ageratum conyzoides confirmation ? for details and differences.
Ageratum conizoides (Blue) ?? 161109 – NSD 101 – efloraofindia | Google Groups : 5 posts by 3 authors. Attachments (1)
This herb is from Periyar Tiger Reserve
Photo taken on 10-5-09
I think this is Ageratum conizoides (Blue coloured flower), but not very sure
Experts pl confirm or id otherwise
Useful link for Ageratum pictures.
thanks for taking lead, i think it is different sp then conizoides,
let some experts from western ghat comment on it
I had careful look at this plant today. This appears to be the cultivated apecies Ageratum houstonianum. Pubescent involucre bracts and longer style arms are characteristic.
WILD FLOWER ID: I wanted to seek ur expertise on the identity of a wild purple flower which grows in clumps in the lower Shiwalik foothills. It is very common and gives of a exotic odour. I am attaching a pix. Could u tell me the name and something about this flower.
– This is an invasive weed – the Mexican Floss Flower [Ageratum houstonianum] a native of Peru & Mexico.
– this is EXOTIC, meaning not a native plant and INVASIVE, which basically means, it has the ability to suppress the indigenous vegetation of an area and multiply itself and a WEED, which basically means, it is an unwanted plant.
efloraindia: 141011 BRS61: Pl. find the attached file contain a photo for id. request.
Date/Time-Location- 06.10.2011, 3 PM
Place, Altitude, GPS- Chinnar (Kerala) Approx. 1200 MSL
Habitat- Urban- along the road side.
Plant Habit- Herb–
In A conyzoides plants and phyllaries are not that densely hairy, and heads are smaller and more spreading
Ageratum conyzoides :: 08-Mar-12 :: Hooghly (WB) SK: Attaching images of Ageratum conyzoides L., a very common wild herb (weed) found on roadside.
Species : Ageratum conyzoides L.
Bengali name : DOCHUNTY
Type : wild herb
Date : 20-Dec-2011, 11.50 a.m.
Place : Hooghly, West Bengal
ID & info help : ‘Plant Groups’ by H. Mukherji
I imagine it is houstonianum. Thicker cordate leaves and longer hairs especially on involucre bracts are clearly seen.
Thank you for the ID. No Bengali name has been given to A. houstonianum in the ‘Plants Groups’, the book that i consult first to obtain any initial ID.
Ageratum houstonianum Mill. ?? : 7 posts by 3 authors. Attachments (6)- around 700 kb each.
Location: Kalimpong, WB, India
Date: 15 May 2018
Altitude: 4100 ft.
Habit : Wild.
i see the south african plant “polka dot plant” in the wild? in picture 2 3 etc. is that ac common occurrence for Hypoestes phyllostachya to show up ??? west Bengal
Yes …, it is !
To me also appear close to images at Ageratum houstonianum Mill.
Ageratum conyziodes ABAPR01/10 : 1 post by 1 author. Attachments (3)
I am not sure of the severity of this goat weed here. It’s more prevalent at lower altitudes (Dharamshala 1500m). Please correct me if I am identifying it wrong.
Ageratum conyzoides (Billygoat Weed, Goat Weed…)
Above Mcleodganj, Dharamshala, HP
10 April 2015
Yes sir !
ageratum conyzoides from Lohari Panipat: A very common weed now days at its bloom Ageratum conyzoides
Image 2662 and 2644 show different leaf bases.
Other than 2644, I agree.
Flower for Id- 01112016SH2 : 4 posts by 3 authors. Attachments (1)
Flower for Id pl.
Location – Guwahati-Shilong Road
Date – 15.10.2016
I think closer to Ageratum houstonianum as per details and keys herein.
Ah ! The cordate leaf, big head !! Yes sir !!
Id of Flower – ID28112019SH3 : 5 posts by 4 authors. Attachments (1)
Flower for id pl.
Location -Mandal (Uttarakhand)
Date – November 2019
Ageratum conyzoides ??
Yes, A. conyzoides or A. haustonianum.
This season is the lean period for flowering but good for landscape views.
Thanks … for the Id.
Yes …, in fact a lean season for flowering but had gone there for bird-watching and captured few flowering plants.
More likely to be Ageratum houstonianum as per comparative images at Ageratum
flowe id…place-ambala cantt….habitat-roadside: Please help me to identify this plant
I think it is Ageratum conyzoides family Asteraceae
Yes Ageratum conyzoides
Ageratum conyzoides I hope
Thanks, …, Details are not clear due to smaller images.
But I think it is more closer to Ageratum houstonianum rather than Ageratum conyzoides as per keys and details herein.
Leaf base as much seen, is not cordate … which I have found every time I met with A. houstonianum. Plus , head size is not really that big !
I wd say A. conyzoides.
Two characters are significant in differentiating these species. Leaves truncate to cordate at base, involucre bracts narrowly lanceolate, less than 1 mm broad, gradually narrowed to subulate tip 1-2 mm long in A. houstonianum. In A. conyzoides leaves are narrowed at base, involucre bracts oblong to oblong-lanceolate, suddenly narrowed at tip to less than 1 mm long point. I have downloaded and enlarged last two images, the involucre bracts also match A. conyzoides. The conflict seems to be too much long hairs on bracts and peduncle.
I guess Ageratum houstonianum is more close.