Quick Facts

Quick facts

• Lesser Roundweed (Hyptis brevipes) is an upright branching herb or sub-shrub growing up to 1.5 m high with tooth-edged leaves and globular flower-heads that are made up of numerous small white tubular flowers.
• It is native to tropical America but it has spread to other tropical high rainfall areas of the world, including south-east Asia.
• It is not known to occur in Australia.
• It has the potential to become a serious problem weed of crops, orchards, pastures, roadsides and wasteland, as well as to invade disturbed native vegetation.

What Does It Look Like?

What is it?

Lesser Roundweed (Hyptis brevipes) is an upright, shortly branched, annual herb or sub-shrub growing up to 1.5 m high. The stems are square in cross section. The leaves are arranged in opposite pairs and are well-spaced along the stem. The leaf blade is narrowly lance-shaped to oblong, 4-8 cm long, 1-2.5 cm wide and sparsely to moderately hairy, with irregularly toothed or serrated leaf margins and borne on a leaf stalk up to 1 cm long. Spherical, pale green flower-heads (6-9 mm in diameter, expanding to 8-14 mm in fruit) occur on stalks 3-15 mm long and are borne in the forks of the leaves, resulting in pairs of leaves and corresponding flower-heads along the stems.

The dense ball-shaped flower-heads are composed of numerous linear to narrowly lance-shaped bracts (modified leaves) 4-6 mm long and small, white, tubular flowers. The flowers are 3-4 mm long, irregularly 5-lobed and 2-lipped and the upper lip has pink spots.

The fruit is a dark brown to brownish black nutlet, minutely wrinkled and about 0.7 mm long (Backer & Bakhuizen van den Brink Jr 1965; Keng 1978; Soerjani et al. 1987 in Waterhouse & Mitchell 1998; Harley 1999).

For further information and assistance with identification of Lesser Roundweed, contact the herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Lesser Roundweed prefers a wet tropical climate and is less common in regions with a seasonal wet/dry regime. It is a weed of plantation crops, orchards, rice, vegetable cultivation, forest margins, regrowth forest and wastelands (becoming abundant in fallow ground) and possibly pastures (Keng 1978; Waterhouse & Mitchell 1998). Lesser Roundweed is commonly found in wet margins of streams and ponds (Zaidan et al. 1991).

Are there similar species?

Knobweed (Hyptis capitata), a weed occurring in north Queensland and the Northern Territory, is very similar in appearance to Lesser Roundweed, except that Knobweed has larger flower-heads at fruiting (15-25 mm in diameter as opposed to 8-14 mm) and a longer flower head stalk (1.5-10 cm long as opposed to 0.5-1.2 cm) (Keng 1978; Flanagan 1998; Waterhouse & Mitchell 1998).

Hyptis (Hyptis suaveolens), a weed widespread across northern Australia, is distinguished by its strong minty smell and its pinkish or lavender-blue flowers that occur in clusters in the leaf axils (Flanagan 1998; DEWHA undated).

Comb Bushmint, also known as Comb Hyptis, Mint Weed, Purple Top or Wild Mint, (Hyptis pectinata), and Marubio, also known as American Bushmint or Black-sesame, (Hyptis spicigera) are rare tropical weed introductions in Australia and differ from Lesser Roundweed in having their flowers arranged in clusters along the tops of the stems or in dense spikes, respectively (Kodela 2008, pers. comm.).

Why Is It A Weed?

What are its impacts?

Agriculture: In overseas environments, Lesser Roundweed inhabits disturbed situations, and if introduced to Australia it could become a weed of cultivation e.g. plantation crops, orchards, vegetable crops; wastelands and possibly pastures, in high rainfall tropical areas. It also has the potential to invade native forest vegetation, especially forest margins and disturbed sites (Waterhouse & Mitchell 1998).

How does it spread?

Lesser Roundweed is spread by seed that is dispersed by wildlife and human activities (Waterhouse & Mitchell 1998).

What is its history in Australia?

Lesser Roundweed has spread as a weed in mostly tropical parts of the world, including Central and South America and in east and south-east Asia (Taiwan and Vietnam to Indonesia). It is a principal weed in Malaysia (Keng 1978; Holm et al. 1979; Waterhouse & Mitchell 1998; PIER 2006; GRIN 2008). It has not been recorded from Australia.

How To Manage It?

Best practice management

Non-chemical control: Prevention: The most effective control is to prevent the introduction of Lesser Roundweed into Australia (Waterhouse & Mitchell 1998; Pheloung 2005; AQIS 2008).

Manual control: Single plants or small infestations should be dug out, ideally before flowering or fruiting. It is recommended that the main roots are removed. If plants are seeding, care must be taken not to disperse the seeds. Seed heads can be bagged and cut off first, and the material burnt.

Chemical control: Larger infestations could be slashed before flowering and potential chemical controls investigated (Kodela & Conn 2008, pers. comm.).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Lesser Roundweed has not been studied in detail but it is a pioneering plant that tends to flower and fruit throughout much of the year (Conn 2008, pers. comm.).

Where Is It Found?

Which states and territories is it found?

Not found in any Australian states or territories

What areas within states and territories is it found?

Lesser Roundweed is not currently found in Australia.

Where does it originate?

Although reported to have originated from Mexico (Keng 1978; Waterhouse & Mitchell 1998), Lesser Roundweed is possibly native to a wider area of Central and South America (GRIN 2008).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT, WA

Is it on the National Alert List for Environmental Weeds?

NO

Is it on the Agricultural Sleeper List?

NO

Names And Taxonomy

Main scientific name

Hyptis brevipes

Other scientific names (synonyms)?