Function

• Roundup is a common broad-spectrum herbicide. It kills virtually any plant it comes in contact with. Roundup can be used to eliminate weeds in vegetable gardens, but only when crops are not actively growing. Fall, winter and early spring are ideal application times.
  
  

Effects

• Weeds treated with Roundup don't die immediately because it takes seven to 10 days to kill root systems. It's main component -- glyphosate -- inhibits the enzymes plants need to grow. Because plants then cannot produce necessary growth proteins, they slowly wilt and die off.
  
  

Considerations

• Always read labels and follow directions carefully when using herbicides. Roundup is most effective when the recommended amount is applied; too little will not effectively control weeds and oversaturating can be dangerous. Also, avoid spraying on windy days so neighboring plants and grass aren't affected.
  
  

Warnings

• Glyphosate may be dangerous to fetal cells. Pregnant women should avoid exposure to this chemical entirely, and everyone should avoid chemical-to-skin contact.