Tansy v ragwort

I am trying to find what tansy looks like. so, I look on the net and I have noticed ragwort is called tansy ragwort.

I have grapes and wanted a companion plant, can i then use tansy ragwort, or does it have to be common tansy?

I don't know about Tansy, but here in the UK ragwort is considered a noxious weed. It is poisonous to livestock and spreads like mad if allowed to seed. Regardless of it's companion properties, or lack of, I wouldn't consider letting it get generally established anywhere.

Even if you don't have livestock now you may want some in the future, and you don't want your land to be a source of airbourne seeds for others.

Mike

These are two different plants. Tansy (Tanacetum vulgare) has flowers that look like yellow buttons (without petals), see pic http://warriorcatsstarclanfanclub.webs.com/photos/warrior-herbs/tansy.jpg. Tansy has been used as a culinary and medicinal herb for centuries although there are some precautions.
Tansy Ragwort (Jacobaea vulgaris, syn. Senecio jacobaea) is a yellow flowering plant, see pic http://www.threatsummary.forestthreats.org/images/threats/Tansy_Ragwort_163.jpg. It's considered as an invasive weed and toxic.

Info on Tansy:
http://landscaping.about.com/od/herbplants/p/tansy_plants.htm

Info on Tansy Ragwort:
http://www.thepoisongarden.co.uk/atoz/jacobaea_vulgaris.htm

Don't plant ragwort! It is highly toxic to most livestock, and to people, and bees love it, but if they have too much of it as a proportion of their forage, their honey is toxic! It's a constant battle on our land.