There are over 30,000 weed species worldwide that can be classified in various ways. Weeds can be classified based on their life span as annual, biennial, or perennial. They can also be classified based on their root system as shallow rooted or deep rooted perennials. Other classifications include how they reproduce, their place of occurrence, the nature of their stem, their origin, and more. Classifying weeds allows for adopting targeted weed management methods for particular weed groups.

2. WEEDS AND WEEDS
CLASSIFICATION
By

3. There are over 30,000 species of weeds
round the world. Out of these about 18,000
are known to cause serious losses. In the list
of world’s worst weeds nutsadge (Cyperus
rotundus) ranks first and hariali (Cynodon
dactylon) second position.

4. The weeds with similar morphological
characters, life cycle, requirements of soil ,
water, climatic condition etc are grouped
together as a class or category. Therefore
classification of weeds is helpful for adopting
weed management methods for particular
group of weeds instead of against an
individual weed species. It is always
economical and practically feasible to
manage the group of weeds as compared to
manage the individual weed species.

5. Long seed life in the soil
Quick emergence
Rapid early growth
No special environmental requirements for
germination
Ability to survive and prosper under disturbed
conditions

6. I) Classification of Weeds based on life span:
Depending upon their life cycle weeds can be
classified as
1) Annual Weeds:
They complete their life cycle within one year or
one season.
a) Kharif Annuals / Kharif Weeds:
They appear with the onset of monsoon (June,
July) and complete their life cycle when rainy
season is over (Oct or Nov) E.g Cock’s comb,
dudhi, math, chimanchara , parthenium etc.

7.  b) Rabi Annuals / Winter Weeds:
 They complete their life cycle during winter season (
Oct/Nov to Feb) E.g Vasanvel ( Chenopodium album) ,
Ghol ( Portulaca oleracea), wild oat etc.
 c) Summer Annuals / Summer Weeds:
 They complete their life cycle during summer season
( Feb to May), Majority of the Kharif seaosn weeds
grow during summer season in irrigated farming E. g
Parthenium , Amaranthus spp. Euphorbia Spp. (
Dudhi) etc.
 d) Ephemerals:
 The short- lived annual weeds are called ephemerals
E. g Niruri ( Phyllanthus niruri). These weed
completes its life cycle within a very short period of
2 to 4 weeks.

10. 2) Biennial Weeds:
They take at least two years or two seasons to
complete their life cycle. They complete
their vegetative growth in first year or
season and produce flowers and seeds in the
next year or season. E.g Wild carrot- (
Daucas carota), wild onion – ( Asphodelus
spp) , Jangli gobhi- (Launea spp).
3) Perennial Weeds:
They continue or grow for more than two years
or several years. Perennial weeds are further
classified as.

14. II) According to Root System:
Depending upon the depth of root system perennial weeds
are classified as
a) Shallow Rooted Perennials:
Those perennial weeds having about 20 to 30 cm deep root
system are called shallow rooted perennial weeds.
E. g Hariali ( Cynodon dactylon), Quack grass ( Agrophyron
repens).
b) Deep Rooted Perennials:
Weeds having about one meter or more deeproot system. E.g
Nutgrass ( Cyperus rotundus), Johnson grass ( Sorghum
holepense ), Acacia spp. wild ber etc.
C) Creeping Perennial
Perennial weeds with vegetative structures (stolons or
rhizomes) that permit them to reproduce asexually
(without seed). field bindweed, quackgrass, Canada thistle

16. III) According to Mode of Reproduction:
a) Simple Perennials: Reproduce mostly by seeds.
E. g Ghaneri- Lantana camara) Acacia- ( Acacia spp),
Wild Ber- ( Zizyphus spp).
b) Bulbous Perennials:
Propagate by underground parts like bulbs, rhizomes ,
tubers etc, as well as seeds.
E .g Cattail ( Pan kanis) (Typha spp),
Nut grass or Nut sedge ( Cyperus rotundus),
Johnson grass (Sorghum halepense).
c) Creeping Perennials:
Spread by lateral extension of the creeping above
ground stem or roots or by seeds.
E .g Hariali – (Cynodon dactylon), Ambooshi – ( Oxalis
litifolia)

20. IV) According to the Place of Occurrence (Habitat):
 Depending upon the place of their occurrence they can be
grouped as under:
1) Weeds of cropped lands: E. g Chandvel, Striga,
Orobanche, Wild rice etc.
2) Weeds of Pastures and grazing lands: E. g Parthenium,
Hulhul (Cleome viscose).
3) Weeds along water channel: E .g Jalkumbhi ( Eichhornia
crassipes) Pandhari Phuli ( Lagasca mollis).
4.Weeds of waste places : Corners of fields, margins of
channels etc., where weeds grow in profusion. Eg.
Gynandropsis pentaphylla, Calotropis gigantea
5. Weeds of playgrounds, road-sides: They are usually hardy,
prostrate perennials, capable of withstanding any amount
of trampling. Eg. Alternanthera echinata, Tribulus terestris

21. V) According to Nature of Stem:
1) Woody Weeds:
These are the woody and semi-woody and
semi-woody rough stem shrubs and are
collectively called brush weeds, E .g Acacia
wild ber, Ghaneri (Lantana Camara) etc.
2) Herbaceous Weeds:
These weeds have green and succulent stem
and common accurence on farm lands.
E.g Math, Cocks, Comb, Dudhi, Parthenium
etc.

22. VI) According to the Origin of Weeds:
1) Introduced or Exotic weeds/ Allien Weeds or Anthrophytes
Many weeds move from the place of their origin by seeds or other
parts to a new area and establish there and become introduces
weeds such introduced weeds are called alien weeds or
anthrophyes.
E .g 1. Parthenium hysterophorus –From U.S.A
2. Solanum elaegnifolium- With food grain.
3. Lantana camera ( Ghaneri) : From Shri-Lanka by birds.
4. Cockleber / Gokhru (Xanthium strumarium) : Native of
America.
5. Orobanche spp. ( Bambakhu)- Europe.
6. Nutgrass ( Cyperus rotundus) chandvel: Eurasia.
7. Water hyacinth – Tropical America ( Introduced in India by
Portuguese)
8. Johnson grass- Asia and southern Europe.
2) Indigenous Weeds:
Origin of majority of tropical weeds is India E .g Cock’s comb,
Dudhi, Aghada, Hariali etc.

23. VII) Facultative Weeds or Apophytes:
Weeds which grow primarily in undistributed or
close communities but may some times
escape to the cultivated fields, It is also
called Apophytes E .g Cactus.

24. VIII) Obligate Weeds:
Weeds which grow or occur primarily in
cultivated field where the land is distributed
frequently. E.g Chandvel ( Convolvulus
arvensis).

25. IX) Noxious Weeds:
The weeds which are undesirable ,
troublesome and difficult to control are
called noxious weeds E.g Nutgrass, Hariali,
Parthenium , Striga, Orobanche, Water
hyacinth etc.

26. X) Objectionable Weeds:
Weeds which produce seeds that are difficult
to separate once mixed with crop seeds are
called objectionable weeds. E. g The mixture
of Argemone Mexicana (Pivala Dhotra) seeds
in mustard. Wild onion in cultivated onion

27. XI) Industrials Weeds:
Weeds invading areas around buildings,
highway, railway lines, fence rows, electric
and telephone pole bases etc are called
industrial weeds. E .g Parthenium,
Reshimkata, Katemath, etc.

28. XII) Poisonous Weeds:
E.g. Parthenium, Datura, Poison, ivy ( Rhus sp),
etc.

33. Classification according to nature of
stem: Depending upon the development of
bark tissues on their stems and branches,
weed can be classified as :
(a). Woody e.g Lantana
(b). Semi-woody and c. Herbaceous species.

34. Classification according to association : It is
classified into three classes:
(a). Season bound,
(b). Crop bound,
(c). Crop associated.

35. Classification according to
situation: Depending upon their occurrences
there can be nine important groups of
weeds.
(a) Crop-land weeds.
(b) Falloland weeds.
(c) Grassland or pasture weeds.
(d) Non-cropland weeds
(e) Aquatic weeds
(f) Forest and woodland woods
(g) Lawn and garden weeds.
(h) Weeds of plantations.
(i) Orchard and vineyard weeds

36. Classification according to soil:
Of the several variable of soil, soil pH is
implicated most frequently with the
distribution of weed species. Weeds, such as
red sorrel, corn sporry and bracken tend to
comminute with weed flora on saline and
alkali soils.

37. Classification according to
climate: Temperature, rainfall, air quality,
humidity and solar energy have pronounced
effect on the distribution of weeds. One
could classify weeds as hillside weeds, weeds
of plains, temperate weeds, tropical
weeds,etc.

38. Facultative and obligate weed: Facultative
weeds are those weeds that grow primarily in
wild communities but often escape to
cultivated fields. E.g. Opuntia Spp. Obligate
weeds on the contrary, occur only in
cultivated or otherwise disturbed land. For
e.g.: Field bind weed.

39. Based on ecological affinities
Wetland weeds They are tender annuals with
semi-aquatic habit. They can thrive as well
under waterlogged and in partially dry
condition. Propagation is chiefly by seed.
Eg. Ammania baccifera, Eclipta alba
Garden land weeds (Irrigated lands) These
weeds neither require large quantities of
water like wetland weeds nor can they
successfully withstand extreme drought as
dryland weeds. Eg.Trianthema
portulacastrum, Digera arvensis

40. C.Dry lands weeds These are usually hardy
plants with deep root system. They are
adapted to withstand drought on account of
mucilaginous nature of the stem and
hairiness. Eg. Tribulus terrestris, Argemone
mexicana

41. Based on soil pH Based on pH of the soil the
weeds can be classified into three
categories. (a) Acidophile – Acid soil weeds
eg. Rumex acetosella (b) Basophile – Saline &
alkaline soil weeds eg. Taraxacum sp. (c)
Neutrophile – Weeds of neutral soils eg
Acalypha indica

42. Based on morphology Based on the morphology of the
plant, the weeds are also classified in to three
categories. This is the most widely used classification
by the weed scientists. (a) Grasses: All the weeds
come under the family Poaceae are called as grasses
which are characteristically having long narrow spiny
leaves. The examples are Echinocloa colonum,
Cynodon dactylon. (b) Sedges: The weeds belonging
to the family Cyperaceae come under this group. The
leaves are mostly from the base having modified
stem with or without tubers. The examples are
Cyperus rotundus, Fimbrystylis miliaceae. (c) Broad
leaved weeds: This is the major group of weeds as all
other family weeds come under this except that is
discussed earlier. All dicotyledon weeds are broad
leaved weeds. The examples are Flavaria
australacica, Digera arvensis, Tridax procumbens

43. Parasitic weeds The parasite weeds are either total or
partial which means, the weeds that depend
completely on the host plant are termed as total
parasites while the weeds that partially depend on
host plant for minerals and capable of preparing its
food from the green leaves are called as partial
parasites. Those parasites which attack roots are
termed as root parasites and those which attack
shoot of other plants are called as stem parasites.
The typical examples are; 1. Total root parasite –
Orabanche cernua on Tobacco 2. Partial root parasite
- Striga lutea on sugarcane and sorghum
Total stem parasite - Cuscuta chinensis on leucerne and
onion 4. Partial stem parasite - Loranthus longiflorus
on mango and other trees.

44. Aquatic weeds: Unwanted plants, which grow
in water and complete at least a part of their
life cycle in water are called as aquatic
weeds. They are further grouped into four
categories as submersed, emersed, marginal
and floating weeds. 1. Submersed weeds:
These weeds are mostly vascular plants that
produce all or most of their vegetative
growth beneath the water surface, having
true roots, stems and leaves. Eg. Utricularia
stellaris, Ceratophyllum demersum

45. 2. Emersed weeds: These plants are rooted in
the bottom mud, with aerial stems and
leaves at or above the water surface. The
leaves are broad in many plants and
sometimes like grasses. These leaves do not
rise and fall with water level as in the case
of floating weeds. Eg. Nelumbium speciosum,
Jussieua repens.

46.  3. Marginal weeds: Most of these plants are
emersed weeds that can grow in moist
shoreline areas with a depth of 60 to 90 cm
water. These weeds vary in size, shape and
habitat. The important genera that comes
under this group are; Typha, Polygonum,
Cephalanthus, Scirpus, etc

47.  . Floating weeds: These weeds have leaves
that float on the water surface either singly
or in cluster. Some weeds are free floating
and some rooted at the mud bottom and the
leaves rise and fall as the water level
increases or decreases. Eg. Eichhornia
crassipes, Pistia stratiotes, Salvinia,
Nymphaea pubescens.