Assessment of Round-up Effects
"Roundup" is now on the label of an assortment of products sold by the same company. It started out just containing glyphosate, but now is available in products with various other herbicides mixed in too. Buyer beware.
Most people really mean the specific ingredient "glyphosate" when they refer to Roundup. (The patent ran out and now many companies sell products with glyphosate in them.)
Glyphosate (by itself) is a "total vegetation killer", meaning it doesn't only kill one type of plant, but almost all families of plants. So, the user must be very careful that it only gets on the targeted plant and doesn't accidentally get blown by wind onto other plants. Users should use a shield to protect desired plants when spraying near them.
Glyphosate doesn't spread through the soil or by water to other plants. It is used extensively worldwide and somewhat controversial as to how safe it is to the environment. It breaks down very quickly, but much research is ongoing about it.