Weeds are classified in several ways, including by morphology, habitat, origin, and life cycle. Morphological classifications include sedges, broad-leaved weeds, ferns, and grasses. Weeds are also classified as terrestrial (including crop land, non-crop land, grassland, lawns/parks, orchards/gardens, plantations, and roadsides) or aquatic (submersed, emergent, and floating). Additional classifications are based on whether weeds are indigenous or introduced, their life span as annual, biennial, or perennial, and the pH of the soil they inhabit. Weeds have adaptations that allow them to outcompete crops, such as producing many

1. Gowtham G
2020713029
I-diploma horticulture
AGR 102-irrigation and weed management
Classification and characteristics of
weeds in different ecosystems

2.  Based on morphology
Weeds are classified
 Based on habitat
 Based on origin
 Based on life cycle
 Based on soil pH

3. Cotyledon characters
Based on morphology, weeds are generally divided into following groups
Sedges: Monocots, Stem is angular & solid, ligules are absent,
Leaves are arranged in spirals around the stem, have modifies
rhizomes
Eg: Cyperus
Broad leaved weeds: Mostly dicots having broad leaves
Eg. Amaranthus spinosus, Portuloca oleracea
Ferns: seedless vascular plants that produce spores
Eg.Marsilea crenata, Salvinia molesta
Grasses: Monocots, Stem is hollow except at nodes, Alternate or
opposite leaves, long, narrow leaves with parallelveins
Eg., Cyanodon

4. Digitaria
Cyperus
Salvinia molesta
Eclipta alba Marsilea crenata

5. Depending upon the place of their occurrence they are classified into:
 Terrestrial
 Aquatic weeds
Terrestrial weeds
Crop land weeds: weeds in field: Eg. Echinochloa

6. Non-crop land weeds: Weeds in waste lands
Xanthium strumarium
Tribulus terrestris

7. Grass land weeds: Eg. Vernonia and Rumex spp.
Rumex crispus
Vernonia cinerea

8. Weeds of lawns & public parks Eg Lippia nodiflora and Eleusine indica.
Lippia nodiflora Eleusine indica

9. Orchard or garden weeds Eg. Euphorbia geniculata, Acalipha indica.
. Euphorbia geniculata, Acalipha indica.

10. Weeds of plantation crops Eg. Mikania micrantha
Mikania micrantha

11. Road side weeds Eg. Lantana camara and Prosopis juliflora
Lantana camara Prosopis juliflora

12. Submersed weeds: Eg.Hydrilla verticillata
Emerged weeds: Eg. Nelumbium speciosum..
Marginal weeds: Eg. Typha, Alternanthera, Ipomea
Floating weeds: Eg. Pistia stratiotes,
Nelumbium speciosum
Typha
Pistia stratiotes
Hydrilla verticillata

13. Indigenous weeds(Apophytes): All the native weeds of the country
are coming under this group and most of the weeds are indigenous.
Eg. Acalypha indica,
Introduced or Exotic weeds : These are theweeds
introduced from other countries. These weeds arenormally
troublesome and control becomes difficult. Eg. Parthenium

14. Parthenium hysterophorus
(From U.S.A)
Lantana camara
(From Sri-Lanka by birds)
Orobanche spp.
( Europe) etc

15. Classification based on association
Root parasites
a. Complete root parasite eg Orobanche (broom rape)
b. Partial root parasite eg Striga spp (witch weed)
Orobanche
Striga spp

16. Stem parasites
a. Complete stem parasite eg Cuscuta (dodder)
b. Partial stem parasite eg Loranthus in fruit crops
Classification based on association
Cuscuta Loranthus

17. Based on life span (ontogeny), weeds are classified as annual,
biennial and perennial weeds.
1. Annuals: They are further classified into
 Kharif season annuals Eg. Setaria glauca
 Rabi season annuals Eg. Chenopodium album
Summer season annuals Eg. Argemone mexicana
 Multi season annuals Eg. Eclipta alba
Setaria glauca Eclipta alba
Chenopodium album

18. They complete the vegetative growth in the first season,
flower and set seeds in the succeeding season and then
dies. These are found mainly in non-cropped areas.
eg; Daucus carota
Daucus carota

19. a) Simple perennial: Ipomea carnea, Lantana camara
b) Bulbous perennial : Wild onion( Allium vineale)
c) Creeping perennial: Sorghum halepense
Sorghum halepense
Ipomea carnea Wild onion

20. Based on pH of the soil the weeds can be
classified into three categories:
I. Acidophile weeds habitat acid soils
 eg. Rumex acetosella, Pteridium spp
Rumex acetosella
Pteridium spp

21. II. Basophile weeds dominate in Saline & alkaline soil
Eg. Salsola spp dominate saline soils where as Cressa erecta,
Sporobolus diander are dominant in alkaline soils.
Salsola spp Sporobolus diander

22. Eg; Acalypha indica
Acalypha indica

23. •Seed production: weeds produce large number of
seeds/plant compared to crops.
•Size of seeds: most of the weeds produce small sized
seed. Since the seeds germinate only from the top layer of
the soils.
•Dormancy: most of the weed seeds have dormancy.
Dormancy acts as a safety mechanism against adverse
environmental conditions. They germinate only when
sufficient amount of rainfall is received. The inhibitory
chemicals from the seeds should be washed away for their
germination.

24. vegetatively by
•Vegetative
rhizomes, stolon’s, bulbs etc. this is
weed production: Some weeds propagate
another mechanism for weeds to
withstand adverse conditions
•Root stem:
• Monocotyledonous weeds depend on seminal roots during seedling stage.
Once nodal roots are developed at subsequent stage, they hold the soil
tightly. It is difficult to remove them either by hand weeding or by inter
cultivation.
• Dicotyledonous weeds have taproot system, the taproot grows deeper into
the soil and the roots store food materials in the roots. At this stage, even if
the shoot is cutoff the weeds may survive.
•Type of photosynthesis: Most of the weeds have C4 type of photosynthesis. It
confers the advantage during moisture stress and also depletes carbon dioxide
to a very low level in the crop micro climate