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You are here: Home / Weeds of Guam

Weeds of Guam

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Acalypha indica

Euphorbiaceae

Acalypha2

Axillary inflorescence showing toothed bracts that enclose female flowers
Male flowers located on upper section of inflorescence
Developing fruits in bracts
Abnormal female flower located at tip of inflorescence
Stems grooved lengthwise
Alternate arrangement with long petioles

Leaf strippling by flea bugs cause the leaves to look whitish silver
A. indica seedlings
Seed capsule (left), seeds (right)

About

Scientific Name: Acalypha indica
Root Word: acalypha = nettle; indica = plants originating from India, East Indies, China
Common Name: Acalypha
Vernacular: Hierba Del Cancer
Similar Species: Acalypha lanceolata Willd.
Origin: Paleotropical
Weed Category: Broadleaves

Description

    Form: small, erect herb with ascending branches

    Stem: longitudinally grooved, pubescent, base becoming woody

    Leaves: alternate, simple, ovate; margins serrate; surfaces glabrous; nerves pubescent, 3-5 at base then pinnately arranged, veins prominent on leaf underside; leaf topside dark green, leaf underside pale green; stipules minute; petioles long, pubescent

    Inflorescence: flowers sessile on erect axillary spikes

    Flower: apetalous, unisexual; female flowers: on lower inflorescence axis, subtended by a toothed green bract, one abnormal female flower also located distally on a long filament; styles: 3, divided into filiform stigmas; male flowers: minute, crowded distally, stamens 8

    Fruit: schizocarp, hispid, 3-lobed

    Seed: ovoid, light brown to tan

    Habitat: waste ground, yards, landscaped areas, facultative upland; tolerates some shade, common on limestone soils, ability to survive arid conditions

    Propagation: seed; regrowth results if root system not completely removed

    Uses: herbal, catnip (roots)

    Fungal Pathogens: Septoria

    Miscellaneous: toxic

Original Source: Prepared by James McConnell and Lauren Gutierrez in collaboration with Lynn Raulerson, Mari Marutani, Robert Schlub, Gregorio Perez, Jean-Marc Guedon, Karl Schlub and Linley Smith.

Alysicarpus vaginalis

Fabaceae

alysicarpus plant

Inflorescence is an erect raceme
Standard petal is large with yellow markings at its base
The wing and keel petal open to expose the reproductive organs
Leaf size and shape is variable


About

Scientific Name: Alysicarpus vaginalis
Root Word: halysis = chain; carpus = fruited; vaginalis = sheathed
Common Name: One Leaf Clover, White Moneywort, Alysicarpus
Synonym: A. nummularifolius sensu Merrill, Hedysarum vaginale L
Origin: Native to tropical America
Weed Category: Broadleaves

Description

    Form: prostrate, low, mat forming

    Stem: pubescent when young, becoming woody at base

    Leaves: alternate, unifoliolate (appears simple), leaflet obovate to oblong, lanceolate (sometimes); apex rounded to subretuse (notched slightly); leaflet size and shape variable; margins entire; lower surface with scattered hairs; stipules 2, persistent, papery

    Inflorescence: terminal or axillary leaf opposed racemes

    Flower: perfect; calyx: sepals 5, tubular, papery, lanceolate lobed, persistant in fruit; corolla: reddish pink to reddish purple; standard (largest petal): obovate to orbicular with yellow markings, wing (two lateral petals): adherent to incurved keel, keel (2 connate petals): with membranous appendages on each side; stamens: 10, diadelphous (in 2 bundles, upper stamen distinct, the other 9 connate into a tube); pistil: style 1

    Fruit: compressed, jointed cylindrical pod (1 - 8 segmented), each segment contains 1 seed; pods clustered on erect stalks; both margins of joints symmetrical; green maturing dark brown to black

    Seed: subglobose or ellipsoid; pale brown to yellowish

    Habitat: lawns, roadsides, disturbed areas, turf, sunny exposed areas, ditches, dry areas, facultative upland; tolerates mowing, grazing and some shading

    Propagation: seed; regrowth results if root system not completely removed

    Uses: herbal

    Fungal Pathogens: Cercospora, Colletotrichum, Gleosporium

    Miscellaneous: “First recorded from the Pacific Islands (Fiji) in 1900” (Whistler, 1995)

Original Source: Prepared by James McConnell and Lauren Gutierrez in collaboration with Lynn Raulerson, Mari Marutani, Robert Schlub, Gregorio Perez, Jean-Marc Guedon, Karl Schlub and Linley Smith., Whistler, Arthur W. 1995. Wayside plants of the islands. Isle Britannica, Hawaii.

Amaranthus spinosus

Amaranthaceae

amarathusspinwhpl

Arrangement of male and female flowers on terminal inflorescence
Closeup of male flower
Closeup of female flower
Male flower at apex of terminal inflorescence
Female flowers at base of terminal inflorescene
Stems often red

Leaf apex has short, spiny tip
Leaf apex has short, spiny tip
Branched inflorescence
Leaves often damaged by loopers (Hymeria recurvialis)
Stems show longitudinal lines and paired spines at leaf base
Seeds (left), enclosed in persistent calyx (right)

About

Scientific Name: Amaranthus spinosus
Root Word: amarantos = unfading, spinosus = spiny
Common Name: Spiny Amaranth, Pigweed
Vernacular: Kulites
Similar Species: Amaranthus viridis L
Origin: probably native to tropical America
Weed Category: Broadleaves

Description

    Form: erect, branched herb

    Stem: green, brown or red (often), angled or with longitudinal lines; paired axillary spines at nodes; glabrous or pubescent

    Leaves: alternate, simple, entire, ovate to oblanceolate; apex emarginate (notched), mucronate (short spiny tip); petioles reddish (often); upper surface glabrous, lower surface veins sparsely pilose, conspicuously veined beneath

    Inflorescence: monoecious; clustered in lower/upper axils and terminal spikes, spikes simple or branched; flowers in lower axils mostly female, flowers in upper third of terminal spike male, in lower two-thirds female

    Flower: green, minute, unisexual; corolla absent; male flowers: stamens 5 opposite sepals; female flowers: stigmas 2, filiform (slender), subtended by a membranous, persistent bract (translucent) and two similar bracteoles tipped with a pale or reddish awn

    Fruit: utricle, opening by a line around the center, enclosed by persistent calyx (often), one seeded

    Seed: ovoid, compressed, reddish brown to black, shiny; dispersed by wind or water; 235,000 seeds per plant

    Habitat: roadsides, lawns, abandoned fields, disturbed areas, forest edges, landscaped areas, facultative upland; tolerates mowing

    Propagation: seed; viability of 19 years, germinates in both light and dark; regrowth from lower nodes reduces effectiveness of hand/ mechanical weeding if root system and stem not completely removed

    Uses: herbal, toxic; leaves used as vegetable greens

    Fungal Pathogens: Cercospora, Colletotrichum, Gleosporium, Phoma

    Miscellaneous: points of spines break off in skin easily; livestock poisoning, toxic; “First recorded from the Pacific Islands (Hawaii) in 1928” (Whistler, 1995), “in Pacific as of 1954, not specific to Guam, generic to Pacific” (Merrill, 1954); ranks 15th in The Worlds Worst Weeds, Distribution and Biology (Holm et al., 1977)

Original Source: Prepared by James McConnell and Lauren Gutierrez in collaboration with Lynn Raulerson, Mari Marutani, Robert Schlub, Gregorio Perez, Jean-Marc Guedon, Karl Schlub and Linley Smith., Holm, LeRoy G., Donald L. Plucknett, Juan V. Pancho, James P. Herberger. 1977. The worlds worst weeds, distribution and biology. Univ. Press of HI, US. Merrill, Elmer D. 1954. Plant life of the Pacific world. The MacMillan Co., NY. Whistler, Arthur W. 1995. Wayside plants of the islands. Isle Britannica, Hawaii.

Amaranthus viridis

Amaranthaceae

Amaranthusviridiswhplt

Inflorescence branched, often tinged red
Alternate leaf arrangment
A. viridis seedlings
Stems are often reddish maroon and striated
Leaf apex has short spiny tip
Seed (left), fruit (right)

About

Scientific Name: Amaranthus viridis
Root Word: amarantos = unfading, viridis = green
Common Name: Slender Amaranth, Green Amaranth
Vernacular: Kulites Apaka
Synonym: Amaranthus gracilis Desf. ex Poiret
Similar Species: Amaranthus spinosus L.
Origin: probably native to Old World tropics, early introduction to Pacific Islands
Weed Category: Broadleaves

Description

    Form: erect, branched (often) herb

    Stem: green to reddish (often), grooved lengthwise, glabrous or pubescent

    Leaves: alternate, simple, ovate to rhombic; surfaces glabrous (mostly), lower surfaces pilose along veins (often); margins entire; leaf tip mucronate (short spiny tip); petioles pink (often)

    Inflorescence: in lower axils compact cymose clusters, in upper axils and terminating plant apex with spike like panicles

    Flower: green, minute, unisexual, monoecious, both sexes intermixed on spikes with pistillate flowers more numerous; corolla absent; sepals 3-4 subtended by 2 tiny bracteoles, bracts and bracteoles whitish and membranous with short pale or reddish awns; female flowers: style 1, stigmas 2-3; male flowers: stamens 3

    Fruit: utricle, subglobose, rugose (wrinkled surface), ruptures irregularly, beaked, one seeded

    Seed: dark brown to black, shiny, compressed slightly; 230,000-500,000 seeds per large plant, can seed when 1 cm. in height; seed dispersed by wind, water, birds, insects, manure, farm machinery; crop seed contaminant

    Habitat: disturbed areas, croplands, roadsides, landscaped areas, waste areas, ditch banks, facultative upland, exposed/sunny areas, moist areas; ability to survive arid conditions

    Propagation: seeds; optimum soil depth of 1 cm.; high moisture results in best responses; variable germination; regrowth from lower nodes reduces the effectiveness of hand, mechanical weeding if root system not completely removed

    Uses: edible, among oldest food crops of New World, leaves cooked, eaten like spinach; herbal

    Fungal Pathogens: Colletotrichum

    Miscellaneous: tree sparrows (Passer montanus) feed on; contains betalain pigment instead of anthocyanins found in most angiosperms; reported to have nodule-like structures on root/stem (unknown microorganisms, possibly nitrogen fixing); illness/death reports as result of Slender Amaranth ingestion (oxalates: sheep, hogs, young calves), toxic; “in Pacific as of 1954, not specific to Guam, generic to Pacific”(Merrill, 1954)

Original Source: Prepared by James McConnell and Lauren Gutierrez in collaboration with Lynn Raulerson, Mari Marutani, Robert Schlub, Gregorio Perez, Jean-Marc Guedon, Karl Schlub and Linley Smith., Merrill, Elmer D. 1954. Plant life of the Pacific world. The MacMillan Co., NY

Antigonon leptopus

Polygonaceae

weed scans006

Leaves with conspicuous veins
Alternate leaf arrangement. young leaves red colored
Pink tepals and yellow reproductive organs in center
Inflorescence of pink flowers
Inflorescence of white flowers
Forms massive root systems

Swollen tuber-like thickenings of root system
Coiled axillary tendril
A. leptopus seedling
Red stems of seedlings
Panicle of many small flowers
Seeds enclosed by persistant tepals

About

Scientific Name: Antigonon leptopus
Root Word: anti = in place of, polygonon = knotweed in reference to affinity to Polygonum (poly=many, gonu=joint)
Common Name: Chain of Love, Love vine, Mexican Creeper, Coral Vine
Vernacular: Cadena De Amor
Origin: native of Mexico
Weed Category: Vines

Description

    Form: climbing vine with axillary tendrils

    Stem: angled, lower stem reddish brown, thickened

    Leaves: alternate, angular, ovate, triangular somewhat, heart-shaped; entire; veins conspicuous, puberlent along veins; tendrils branched

    Inflorescence: racemes, many flowered

    Flower: perfect; tepals: 5-6, membranous, pink to deep pink or white; stamens: 7-9; styles: 3, stigmas capitate

    Fruit: achene, angled; enclosed by persistant petals

    Seed: prolific seed producer

    Habitat: disturbed areas, roadsides, landscaped areas, facultative uplands; climbs high in trees; ability to survive arid conditions

    Propagation: seed; regrowth from tuber reduces effectiveness of hand/mechanical weeding if tuber not completely removed

    Uses: edible underground tubers, herbal

    Fungal Pathogens: Colletotrichum, Pestalotia

    Miscellaneous: aggressive weed; Invasive Plants of Micronesia List

Original Source: Prepared by James McConnell and Lauren Gutierrez in collaboration with Lynn Raulerson, Mari Marutani, Robert Schlub, Gregorio Perez, Jean-Marc Guedon, Karl Schlub, and Linley Smith.
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