I first noticed this weed at the beginning of secondspring last year when I was out photographing plants to use in weed profile posts. At first I was pleased – it looked a lot like one of the edible chrysanthemums. Further checking however and I discovered it was Senecio vulgaris, the common groundsel, and very definitely NOT edible at all. The Asteraceae is a large family and always, *always* worth checking the details. There are references to it having been used in herbal medicine – it’s even listed in Culpeper’s – and some of these uses may possibly even be effective. But when you read them closely you notice that they are either external uses (poultices and washes), or they are treatments that depend on the plant being just enough toxic to make you throw up or have some other bodily reaction that sorts out your medical problem as a side effect. I am not totally opposed to using toxic reactions as part of medicine – digitalis is the well-known poster child – but I’d rather it be done with controlled quantities and known purities than picking weeds from the roadside.
Groundsel is toxic to humans, and also to livestock. Interestingly though it’s very popular with birds and its seeds were (still are?) used in commercial bird food mixes for small birds – canaries, finches and the like. This is probably how it has ended up becoming a world-wide weed of such global distribution that it’s not always entirely clear whether it was native to an area before European colonisation or not. Senecio comes from Senex, meaning old man, as the flowers do that lovely puffball thing of turning into a white head of hair and then going bald as the seeds blow off in the wind. They don’t actually float that far though, mere metres usually, so it’s unlikely that wind dispersal got them round the globe. Birds, however – the seeds have wonderful persistence, they last for several years, a significant percentage pass through birds digestive systems still able to germinate. And birds think they’re tasty. Between bird spread and being carried intercontinentally on ships as contaminants in bags of grain, groundsel’s gotten just about everywhere.
It’s an interesting weed in its habits. The seeds last for years and don’t need to germinate at the first opportunity. It loves disturbance – you mostly find it on roadsides, spare lots, random forgotten corners of the urban sprawl. It doesn’t compete heavily – it’s one of nature’s collaborators rather than competitors – so you’re more likely to find a few groundsel plants mixed in with lots of other weeds than a big field of them. Unless that field has been recently disturbed or dug up, which would encourage large numbers to germinate. Groundsel also loves warm rain. I found a reference online saying that rain temperature is a better predictor of seedling emergence than soil temperature. And that’s borne out by my observations so far – we’ve had some good autumn rain this year, early enough for it to still be warm, and I’ve got groundsel plants growing well already. Last year I didn’t see them til well after midwinter. Though I acknowledge that I wasn’t looking for them either so it’s possible I saw them and didn’t know what I was seeing.
Getting rid of groundsel becomes tricky, because digging it up or weeding it creates disturbance which means more seeds in the area will germinate and you’ll get a new crop. That’s not totally a bad thing, it just means you have to weed-and-dig again in two weeks’ time (and then again, and then again). Solar soil sterilisation will successfully cook the seeds so that could be of use in an area you know had groundsel in a previous season. In Perth, groundsel’s not usually an all-year weed. Its germination is mainly limited to autumn and spring and it can’t get all the way through our dry summers. So there’s a good window for soil sterilisation. But, because it’s not a competitor, sometimes it doesn’t need to be removed at all. I have no livestock grazing here and I’m happy to leave some for the birds even though the neighbourhood cats have pretty much ensured we have no small seed-eaters in our immediate vicinity. However, I refuse to let it grow in the vegie beds where people go and munch random greenery on a regular basis. It’s also a host for one of the root-rot fungii that can affect the flowers and vegetables we want to have growing, so it’s not good to have in growing beds that we’re leaving fallow for the season (it does love fallow beds!).