I am pretty sure most of us know ragwort when we see it; it is both common and infamous as supposedly being the cause of death of thousands of animals a year! I am, of course, being facetious but I do find some of the unjustified things said about our native flora and fauna rather irksome and feel an inbuilt need to come to their defence.
If you do know ragwort when you see it, can you tell the difference between common ragwort and marsh ragwort (Senecio aquaticus)? I ask this because in my days leading walks I found a general 'ragwort is ragwort' belief amongst those with me and when I pointed out marsh ragwort there was both surprise that there are different species of ragwort and that, although similar, they are different. Marsh ragwort is much shorter than common ragwort and more branched, common ragwort tends to be an upright plants whereas the branched marsh ragwort is somewhat more disparate. Whilst the individual flowers are similar they form a much looser cluster on marsh ragwort than the much tighter cluster on the common ragwort. Marsh ragwort has a reddish stem and the leaves are a darker green than its cousin so there are plenty of differences. If you are still in doubt then common ragwort grows in dry conditions whilst marsh ragwort likes damp meadows and grassy places.
The question of toxicity is complex one and as I am not a chemist I am not going to comment but it seems marsh ragwort has similar chemical properties to common ragwort but, in general it, goats and pigs eat it with no ill effects, cows find it distasteful and horses and sheep refuse to touch it. On the other hand rabbits are fond of it, birds eat the seeds (and you can buy the seeds to feed to caged birds) and, of course, insects love it, especially the caterpillars of some moths which not only take pollen but eat the leaves. Studies show that a horse or a cow would need to eat 7% of their own body weight in ragwort before it would damage them. The case for the defence rests!