By Cositere S
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By Cositere S COSITERE OCT 2011 1 WEEDS Definition: Plants growing where they are not wanted (out of place). Effect of weeds Retard growth due to competition Loss of quality Interfere with harvesting High cost of control Delay crop maturity Increase crop lodging Keep pests and diseases Yield reduction COSITERE OCT 2011 2 Characteristics of weeds Ability to regenerate when cut to fractions. Adapted to short and long seed dispersal. Ability to produce large amounts of seeds. Short vegetative growth. Strongly competitive and aggressive. Seed dormancy. COSITERE OCT 2011 3 Weed classification ➢Life cycle: annuals, biennials, perennuals. ➢Habitat: agrestal, ruderal, aquatic, upland, parasitic. ➢Mophology: dicots, monocots. ➢Physiology: C3, C4. ➢Binomial nomenclature: the scientific way of which uses the genus and species. COSITERE OCT 2011 4 Differences between grasses and broad leafed weeds GRASSES BROAD LEAFED WEEDS Have fibrous roots Have distinct tap root Have distinct nodes Have no nodes Leaf is supported by a sheath Have leaf petiole Veins run parallel to the leaf Have a net venation Have dull coloured flowers Have bright coloured flowers Have no visible apical meristem Have visible apical meristem COSITERE OCT 2011 5 Bidens pilosa Family: Asteraceae Genus: Bidens Species: B. Pilosa Common names: Black jack, cobble’s pegs Venaculla names: Tsine, Mhuuru, Kanzota, Mbuu COSITERE OCT 2011 6 Bidens pilosa Physical Characteristics A weed with angular dark green stem and spiky seeds. Seedlings: have narrow, pointed and elongated cotyledons which can be dark purple underside. COSITERE OCT 2011 7 Tagetes minuta Family: Asteraceae Genus: Tagetes Species: T. minuta Common names: Mexican Marigold, Mint Marigold, Wild Marigold, or Stinking Roger Venaculla names: Kambanje, Mbanji. COSITERE OCT 2011 8 Tagetes minuta Physical Characteristics This type of marigold may grow to 0.6–1.2 meters tall. Leaves are feathery are jagged. Seedlings : have broad, round tipped cotyledons which smell when rubbed. COSITERE OCT 2011 9 Schkuhria pinnata Family: Asteraceae Genus: Schkuhria Species: S. pinnata Common names : Dwarf marigold, False threadleaf Venaculla names: Ruhwahwa COSITERE OCT 2011 10 Schkuhria pinnata Physical Characteristics Delicate, branched annual herb. Leaves mostly pinnately dissected . Flowers have deep yellow with green bracts. COSITERE OCT 2011 11 Cynodon dactylon Family: Poaceae Genus: Cynodon Species: C. dactylon Common names: Bermuda grass, couch grass, quick grass. Venaculla names: kapinda, tsangadzi, uqhethu. COSITERE OCT 2011 12 Cyperus eragrostis Family: Cyperaceae Genus: Cyperus Species: C. eragrostis Common names: Venaculla names: COSITERE OCT 2011 13 Cyperus eragrostis Physical Characteristics It is a green sedge with tall(25–90 cm) , erect stems, and long, thin, pointed leaves. Its flowers are found within tough, rounded, greenish-yellow or beige spikelets COSITERE OCT 2011 14 Cleome monophylla Family: Cleomaceae Genus: Cleome Species : C. monophylla Common names: Spindle pod Venaculla names : Mujakari , Musemwasemwa, Mutsvandimire, Mutyangetyange COSITERE OCT 2011 15 Cleome monophylla Physical Characteristics Erect annual herb, occurring in a wide variety of habitats. Stems and leaves have hairs. Leaves simple, narrowly lanceolate. Inflorescences terminal with bracts similar to the leaves. Flowers mauve (rarely white) with purple markings on the petals. Seedlings: cotyledon leaves are short , rounded and purple under leaf. COSITERE OCT 2011 16 Datura stramonium Family: Solanaceae Genus: Datura Species: D. stramonium Common names: Thorn apple , jimson weed, devil's trumpet, devil's weed, stinkweed, devil's cucumber. Venaculla names: Chowa, COSITERE OCT 2011 17 Datura stramonium Physical Characteristics It is an erect annual herb forming a bush of 1–1.5 m tall. The leaves are soft, irregularly undulate, and toothed. Flowers are trumpet-shaped, white to creamy or violet. The egg-shaped seed capsule is either covered with spines or bald. At maturity it splits into four chambers, each with dozens of small black seeds. Seedlings: have narrow, long and pointed cotyledon leaves. First true leaves are shorter. COSITERE OCT 2011 18 Physalis angulata Family: Solanaceae Genus: Physalis Species: P. Angulata Common names: Wild gooseberry Vernacular names: Muguzibheri. COSITERE OCT 2011 19 Physalis angulata Physical Characteristics It is a common annual herb with ovate to lanceolate leaves, growing up to 4 feet tall. It produces small, orange edible fruits (berries) eaten by animal and human alike. Seedlings: The cotyledons leaves are opposite each other, ovate with reddish petioles and without a distinct mid vein. COSITERE OCT 2011 20 Galinsoga parviflora Family: Asteraceae Genus: Galinsoga Species: G. parviflora Common names: Chick weed, gallant- soldier. Venaculla names: Chaarendo COSITERE OCT 2011 21 Galinsoga parviflora Physical Characteristics The weed is an annual growing up to 0.6 m. It is in flower from May to October. Seedlings: cotyledon leaves are rounded, have an inward cleft at the tip and have long petioles. COSITERE OCT 2011 22 Chenopodium album Family: Amaranthaceae Genus: Chenopodium Species: album Common names: Fat Hen, wild goosefoot. Venaculla names: Kasunika. COSITERE OCT 2011 23 Chenopodium album Physical Characteristics An annual, growing up to 1 metre tall, the stems usually multi-branched. Leaves are grey-green, oval to diamond shaped, have shiny white hairs on top. Spikes of small greenish-white flowers appear from June to October attached to the leaf axils at the top. COSITERE OCT 2011 24 Conyza albida Family: Asteraceae Genus: Conyza Species: C. albida Common names: Fleabane Vernacular names: Gonzo COSITERE OCT 2011 25 Conyza albida Physical Characteristics An erect annual herb, usually about 1m high and single stemmed but large plants may reach 2m and be branched. Stems and leaves are finely hairy. Leaves are grey green and narrow. Flowers are carried in branched heads with each cluster of tiny flowers being enclosed in a series of narrow green bracts. Typical daisy spherical clusters of small seed with a parachute of fine hairs. COSITERE OCT 2011 26 Hibiscus meeusei Family: Genus: Hibiscus Species: meeusei Common names: Stockrose Vernacular names: Sosoori, Ugangampunza COSITERE OCT 2011 27 Hibiscus meeusei Physical Characteristics Annual or biennial herb of 1-1.5m, usually branched from the base. Leaf petioles are up to 12 cm; lamina (of middle leaves) ovate in outline and serrated. Flowers are 3-6 cm in diameter, yellow with dark red centre. COSITERE OCT 2011 28 Oxalis latifolia Family: Oxalidaceae Genus: Oxalis Species: O. Latifolia Common names: Purple garden sorrel, salt weed. Vernacular names: Chimunyu. COSITERE OCT 2011 29 Oxalis latifolia Physical Characteristics This is a perennial herb growing from a system of small bulbs and spreading via stolons. • There is no stem. • The leaves arise on long petioles from ground level, each made up of three widely heart-shaped leaflets. • The inflorescence is an array of several flowers, each with five pink petals. COSITERE OCT 2011 30 Oxalis corniculata Family: Oxalidaceae Genus: Oxalis Species: corniculata Common names: Vernacular names: COSITERE OCT 2011 31 Amaranthus hybridus Family: Amaranthaceae Genus: Amarathus Species: A. hybridus Common names: Pigweed. Vernacular names: Bonongwe, Mowa. COSITERE OCT 2011 32 Amaranthus hybridus Physical Characteristics Amaranthus hybridus is a annual growing to 2 m. It is frost tender. It is in flower from July to September. The flowers are monoecious and are pollinated by wind. COSITERE OCT 2011 33 Rottboellia cochinchinensis Family: Poaceae Genus: Rottboellia Species: cochinchinensis Common names: Shamva grass, Itch grass. Vernacular names: Vave. COSITERE OCT 2011 34 Rottboellia cochinchinensis Physical Characteristics It is a profusely tillering erect annual grass that reaches heights of 4 metres. It is characterised by pale, green- coloured foliage and brace roots near the base of the plant. Has siliceous hairs on the leaf sheath that can penetrate and irritate the skin. COSITERE OCT 2011 35 Cyperus rotundus Family: Cyperaceae Genus: Cyperus Species: C. rotundus Common names: Purple nutsedge Vernacular names: Ndave COSITERE OCT 2011 36 Cyperus rotundus Physical Characteristics It is a rhizome perennial plant with numerous tuberose thickenings helping plants to breed. • Stems grow up to 50cm high, usually single, with dark green basal leaves which spread at ground level. • The seeds germinate in lower places under sufficient moisture. • One plant is able to form about 10 000 seeds and to 100 tubers. • Tubers are big, elongated, rough and have a turpentine taste. COSITERE OCT 2011 37 Cyperus esculentus Family: Cyperaceae Genus: Cyperus Species: C. esculentus Common names: Yellow nutsedge, watergrass. Vernacular names: Pfende COSITERE OCT 2011 38 Cyperus esculentus Physical Characteristics Cyperus esculentus is a perennial growing to 0.9 m at a fast rate. The flowers are pollinated by wind. COSITERE OCT 2011 39 Commelina benghalensis Family: Commelinaceae Genus: Commelina Species: C. benghalensis Common names: Wandering dew Vernacular names: Goche, Indabane. COSITERE OCT 2011 40 Commelina benghalensis Physical Characteristics Commelina benghalensis can be an annual or perennial herb. Leaves are ovate, 2.5-7.5cm long, 1.5-4cm wide, with parallel veination. The leaf sheath is covered in red and sometimes white hairs at the apex . Flowers are funnel shaped and the upper two flower petals are blue to