IN THIS PPT YOU WILL LEARN ABOUT CLASSIFICATION OF WEED BASED ON ONTOGENY/LIFE SPAN AND NATURE OF STEM.

1. Presented by : Pratyush Panda[201]
G.Harshavardini[202]
Guided by: Dr. Rajesh Shriram kalasare
CLASSIFICATION OF
WEEDS BASED ON
ONTOGENY & NATURE
OF STEM
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2. Based on life span (ontogeny), weeds are classified as annual, biennial and perennial weeds.
Summer and kharif annuals: Trianthema sp. (carpet weed)
Winter annuals: Chenapodium album ( Lamb's-quarters)
Multi-season annual (All seasons)
A. Annuals: Completes its life cycle within one year or one season and propagate by seeds. They may be Kharif
annuals, winter annuals and summer annuals.
Digera arvensis (digera)
Setaria glauca (yellow fox tail)
Vicia spp (vetches)
Avena fatua (wild oat)
Phalaris minor (little seed canary grass)
Echinochloa colonum
Eclipta alba
Eleusine indica
Phyllanthus niruri
Classification based on life cycle/ontogeny:
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3. B. Biennial weeds: Complete their life cycle within two years/ two seasons, 1st year
vegetative growth – Rosette stage. 2nd year produced inflorescence called bolting.
They may propagate either by seeds or vegetative parts or by both. Biennials
generally do not come up in annual crop fields but they infest perennial crop fields,
pastures, lawns and orchards. Eg. Daucus carota , Alternenthra echinita
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4. Grow more than two years. Reproduce vegetatively from under ground and specialized organs. First
time they come to flowering in 2nd year and there after flowering every year. Difficult perennial
weeds also known as pernicious weeds. Eg. Cynodon dactylon (Bermudagrass) and Agropyron repens
( quackgrass )are shallow rooted perennials where as Cyperus rotandus . (Purple nut sedge) Sorghum
halepense (Johnson grass) are deep rooted Perennials .
1.Simple perennials: These reproduce solely by seeds but when roots or crown are cut, the cut pieces
may produce new plant Eg. Ipomea carnea and Lantana camera
2. Balbous perennial: These propagate by bulbs or bulblets as well as by seeds. Eg. Wild onion and wild
garlic (Allium vineale).
3.Creeping perennials: These propagate by means of rhizomes, stolons, spreading roots as well as seeds.
Eg. Convovulus arvensis, Agropyron repens (quack grass) and Sorghum halepense ( Jhonson grass)
C. Perennial weeds
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5. Classification based on nature of stem:
Depending upon development of bark tissue on their
stems and branches weeds are classified into woody,
semi-woody and herbaceous weeds.
1.Woody weeds: Weeds include shrubs and under shrubs
and are collectively called brush weeds. Lantana camera,
Prosopis juliflora, Zizyphus rotundifolia (wild plum) are
examples for brush weeds.
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6. Semi-woody weeds: Croton sparsiflorus is semi woody weed.
Herbaceous weeds: Weeds have green, succulent stems are of most common
occurrence around us. Eg. Amaranthus viridis and Chenopodium album.
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7. THANK YOU!
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Reference
Abbott, R. J., L. C. Smith, R. I. Milne, R. M. Crawford, K. Wolff, and J. Balfour. 2000. Molecular analysis of plant migration and refugia in the
Arctic. Science 289: 1343–1346. Abrahamson, W. G. 1980. Demography and vegetative reproduction. Pp. 89–106 in O. T. Solbrig (Ed.),
Demography and Evolution in Plant Populations. University of California Press, Berkeley. Ackakaya, H. R., M. A. Burgman, and L. R.
Ginzburg. 1999. Applied Population Ecology: Principles and Computer Exercises Using RAMAS Ecolab, 2nd ed. Sinauer Associates,
Sunderland, MA