Lecture 5 Classification of Weeds

 

Lecture 5

Classifications of Weeds

1. Classification on the based-on life cycle

A. Annual weed (एक वर्षीय खरपतवार)

ü  Weeds that live only for a season or a year and complete their life cycle in that season or year are called as annual weeds.

ü  These are small herbs with shallow roots and weak stem. Produces seeds in profusion and the mode of propagation is commonly through seeds.

Ø  Kharif Season

• Commelina benghalensis, Boerhavia erecta, Trianthema monogyna, Solanam nigram, Amaranthus viridis

Ø  Rabi Season

• Chenopodium album, Anagalis arvensis, chinopdium murale, Asphodelus tenuifolius, Phalaris miner     

B. Biennials Weeds

ü  It completes the vegetative growth in the first season, flower and set seeds in the succeeding season and then dies.

ü  These are found mainly in non-cropped areas. Eg  Daucus carota, Fumaria parviflora.

C. Perennials Weeds

ü  Perennials live for more than two years and may live almost indefinitely.

ü  They adapted to withstand adverse conditions. They propagate not only through seeds but also by underground stem, root, rhizomes, tubers etc. And hence they are further classified into

v  Woody Weeds (कष्ठिल खरपतवार)

ü  The weeds of this class have tough stems.

ü   Especially it includes perennial shrubs and wild trees.

ü  For the first few years, they do their vegetative growth, then for many years continuously they produce seeds like Zizyphus rotandifolia, Sachharam spontanium, Calotropis gigantia and Achyranthus aspera.

v  Herbaceous weed

ü  The weeds belonging to this category grow their vegetatively in the first year and produce seeds in the second year.

ü   Their stems and branches are soft like Cyperus rotandus, Cynadon dectylon and Convolvulus arvensis etc.

2. Classification Based on Cotyledons

1. Monocot Weeds

ü  On plucking the seeds of these weeds, the seeds do not break into two groups.

ü  Cynadon dectylon, Cyperus rotandus, Avena fatua, Sacchharam spontanium, Asphodelus tenuifolius etc.

2.  Dicot Weeds

ü  On breaking the seeds of these weeds, the seed splits into two groups.

ü  Chinopodium album, Anagalis arvensis, Euphorbia hirta & macrophylla, Solanam nigram, Convulvulus arvesis.

     3. Classification Based on Weed Crop Relations

1. Absolute Weeds

ü  All annual, biennial and perennial weeds come in this category, which always harm the farmer.

2.  Relative Weeds

ü  In this category, those plants of the same season, which the farmer does not sow in the field, they grow on their own, are called relative weeds.

ü  Like barley, gram and mustard in wheat field.

1. Mimicry Weeds

ü  Weeds like wild paddy in the field of paddy, wild oats and Phalaris miner in the field of wheat are found in the external morphology with the crop plants and keep growing along with the crop, they are called Mimicry weeds.

2. Specific micro climate Weeds

ü  Kansani weed requires shady and cool moist climate. This climate is found in the crops of Berseem and Lucerne.

ü  The seeds of wild onion and Phalaris miner ripen at the same height and at the same time as those of the winter grain crop.

ü  They are mixed with seeds when the crop is harvested.

C. Rogue

ü  When a plant of another species of a crop grows in the field without being sown, it is called Rogue, like a plant of UP-262 in the wheat crop of HD - 1553.

ü  To maintain the purity of a particular species, uprooting such unwanted plants from the field is called Rouging.

4. Classification Based on Propagation Methods

1. Weeds which propagate by seed

ü  जंगली चौलाई (Amaranthus viridis), ज्वासा (Alhagi comilorum), कृषननील (Anagalis arvensis), प्याजी (Asphodelus tenuifolius), दुद्धि (Euphorbia hirta & macrophylla), हज़ारदाना (Phyllanthus niruri) इत्यादि खरपतवार केवल बीजों के द्वारा ही जनन करते है ।

2. Propagate by Vegetative parts

ü  By Roots (जड़ों द्वारा) - हिरणखुरी (Convolvulus arvensis)

ü  By Stem (तने द्वारा) - कुछ खरपतवार जैसे दूब जिनके तनों पर गाँठे पाई जाती है इन गांठों से नये पौधे तैयार होते है, दूब व हिरणखुरी इसका अच्छा उदाहरण है ।

ü  By Rhizomes and tubers - मौथा नामक खरपतवार की जड़ों मे कन्द (Tuber) 1.6 cm आकार  तक पाये जाते है । इन्ही कन्दों से नए पौधे तैयार होते है ।

ü  काँस एवं सरपट नामक खरपटवारों की जड़ों मे प्रकन्दों (Rhizomes) द्वारा नए पौधे तैयार होते है ।

ü  By Leaves - Trianthema monogyna

5. Classification Based on Growth Habit of Stem

1. Erect Weeds (सीधे बढ्ने वाले खरपतवार)

ü  Most of the annual weeds come in this category. Their stems grow straight.

ü  such as Chenopodium album, Amaranthus viridis, Anagalis arvensis.

2. Prostate Weeds (फैलने वाले खरपतवार)

ü  Due to the weak stems of these weeds, they spread on the ground and walk. such as Tribulus Terristaris, Trianthema monogyna, Stelleria media (चिकवीड)।

3. Creeping Weeds (रेंगने वाले खरपतवार)

ü  The stems of these weeds crawl on the ground. Roots emerge from the knots of their stems. Like Cynadon dectylon, Partulaca quandrifda (नूनिया)

4. Trailing Weeds

ü  The stems of these weeds are weak, they climb up on the support of crop plants.

ü  Like Convolvulus arvensis, Vicia hirsuta (मुनमुना), Latharus aphaca (चटरी मटरी).

5. Climbing Weeds (आरोही खरपतवार)

ü  These weeds have tendrils to cling to the crops. Sephalendra indica (कँदुरी)

6.  Classification based on Weed Utility

1. As fodder
2. As medicines
3. To prevent soil erosion
4. As a shed
5. As a Ornamental plant
6. As fencing

7. Classification based on Soil and Water Relationship

1. Weeds of Desert

ü  Alhagi comelorum,

B. Weeds of water-logged soil

ü  Echornia crassipes जल कुंभी, Echinocloa colonum (साँवाँ घास)

C. Weeds of Marshy land

ü  Sachharam spontanium

D. Weeds of Uncultivated areas

ü  Sachharam spontanium, Lentana camera, Dhatura strumarium.