About the Weeds

Each plant species has the potential to become weeds . Potential as weed plants tend to have certain characteristics that enable it to easily spread and capable of causing widespread disruption and loss ( Djafarudin , 2001)a. Are subjective ( based on human interest / anthropocentric )
 Weeds are :

• Plant the wrong place
•  Plant unwanted
• Plants are not desired
• Plants are not cultivated
• Plants that harm
• Plant unsightly
• Plants that have a greater negative value than positive values ​
• Plants that have known benefits .

b . impersonalWeeds are plants that have adapted to the artificial habitat and cause disturbance to any human activity .Connection with the cultivation of weed is a plant whose existence can cause disruption and damage to crops and human activity in managing their farm ( Yudiarti , 2007).Characteristic than weeds include :

• Rapid growth
• Have a strong competitive edge in getting their needs factors
• Have a great tolerance to extreme environmental conditions
• Have the power of a large breed or vegetative and generative
• Breeding tool easily spread via wind, water, and animals, and
• Seed dormancy has properties that enable it to survive in unfavorable conditions ( Nasution , 1986) .

Although crop growth requirements are met when the disruption will get damaged by declining results can even crop failure . This interference is due to weed around plants cultivation . Losses caused by weeds can ( 1 ) reduce crop yield ( quantity and quality of products ) through competition : water , nutrients , light , CO2 , and space to grow , competition in the dimensions of space and time . ( 2 ) Inhibits / suppress the growth of crop plants with poison even excrete alelopat . Some examples of weeds that could inhibit the growth of other plants , such as : 
sembung vine ( Mikania sp . ) Excrete excretion ( phenol and depressed the growth of rubber ( Wong , 1964 cit . Nasution ,  flavones ) 1986) ;• alang - alang ( Imperata cylindrica ( L. ) Beauv . ) Produces phenol ,• Juglans nigra produces hydroxy juglane ,• Puzzle ( Cyperus rotundus L. ) produce salicylic acid ,• Salvinia leucophylla issued terpenenes compounds ,• Encelia farinosa release 3 - acetyl - 6 - methoxy benzaldehyde ,• Artemisia vulgaris produce substances that are toxic and volatile , and• A. absinthium absinthine release .( 3 ) fertilization, sanitation and plant maintenance Complicates scarify the soil, as well as pest control. ( 4 ) Inhibits water flow and damaging irrigation channels. ( 5 ) Reduce water supplies in reservoirs ( transpiration ), ( 6 ) reduces the capacity of water in irrigation channels and shelter ( rivers, ditches , reservoirs, dams , ponds , pools, etc. ) due to sedimentation. ( 7 ) Disturbing and complicate human activity  field sanitation in cultivation since pratanam to postharvest / land cultivation. ( 8 ) As a substitute host for insects pests and disease pathogens . Increased costs for pest control and plant diseases . Invaded by weeds and pests cause plant diseases cause similar to that attack plants. Scirpus maritimus live Piricularia orizae, the organism that causes blight disease ( blast ) rice. Most herbaceous weeds are host plants for green and brown leaf borer ( Nephotettix impiticepts and Nilaparvata lugens ). Among the cropping season, the weeds act as host plants for the insect insects that ensures the next planting season. ( 9 ) Potential health disorders . Several species of weed pollen causes allergies and some species cause skin inflammation . Some species of weeds that cause pollen allergies, among others Cynodon dactylon, Eleusine indica , Imperata cylindrica, Amarantus spinous, Tridax procumbens, Mimosa pudica, and Cyperus rotundus .
Weeds can be detrimental not only weeds but also can have a positive role include :

• Protecting the soil from erosion : Imperata cylindrica , Paspalum conjugatum , spread on the surface Axonopus compressus , Cynodon dactylon and soil . 
• Fertilize the soil : Centrosema pubescens , Pueraria javanica , Calopogonium mucunoides , and C. caeruleum .

Weeds classification1 . Based on morphological characteristics and response to herbicides :

• Grasses ( herbaceous ) : Family Gramineae
• Sedges ( Tekian ) : Family Cyperaceae
• Broadleaf Weeds ( leaf width ) : In addition to grass & Tekian
• Fern ( of Pakistan ) : comes from a family of Pakistan / ferns

2 . Based on Life Cycle ( Age )

• Annual Weeds ( Weeds season ) , characteristics : age < 1 year , seed propagation organs , usually die after seed ripe , seed production regeneration . Example :  abundant Eleusine indica , Cyperus Iria , Phyllanthus niruri , etc. .
• Biennial Weeds ( Weeds dwimusim ) , Characteristics: Age 1-2 years , the first year forming vegetative organs and produce seed the second year . Example : Typhonium trilobatum and Cyperus difformis .
• Perennial Weeds ( Weeds annual ) , Characteristics: Age > 2 years , or generative and vegetative propagation , vegetative organs tend to grow at the end , when the organ  vegetative apical dominance is dismembered all the shoots can grow . Example : Imperata cyllindrica , Chromolaena odorata , and Cyperus rotundus .

3 . by Habitat

• Terrestrial Weeds ( Weeds land ) , Characteristics: Grows in dry land and can not stand waterlogging . Example : Axonopus compressus , Ageratum conyzoides , and Cyperus rotundus .
• Aquatic Weeds ( Weeds water ) , Characteristics : Part / whole life cycle in the water , generally when drought die . Example : Pistia stratiotes ( Floating Weeds ) , Monochoria vaginalis ( Emergent Weeds ) , Ceratophyllum demersum ( Submergent Weeds ) , dam Polygonum piperoides ( Marginal Weeds ) .
• Areal Weeds ( Weeds riding on the plant ) , Characteristics: Growing always stick / ride on other plants and usually disturbing . Example : Drymoglossum heterophyllum ( epiphytes ) , Loranthus pentandrus ( Hemiparait ) , and Cuscuta campestris ( Hiperparasit ) .

4 . By Type / How Growing

•  Erect / grow upright : Boerhavia erecta
• Creeping / growth spread : Paspalum conjugate
• Climbing / climb : Meremia hirta

5 . Based on Stem Structure

•  Herbal / no woody : Panicum repens
• Vines / Slightly woody : Mikania micrantha
• Woody Weeds / Woody : M. affine