Hypericum possibly?

[Paul T]

Howdy All,

It may be a result of some decent rain late this spring after such dreadful drought (which unfortunately still isn't over, unless we get a lot more rain) but there are a profusion of yellow "weeds" in the paddocks around Canberra at the moment.  I have no idea whether these are perennials that are always there and are just thriving this year, or whether they are annuals that have popped up in all the spaces left by the grass drying in the drought, but either way I haven't noticed these plants before or if I have not anywhere in these numbers.  Because of this I have no idea whether these are native to this area and just in a good cycle this year, or whether they are an "alien invader" from elsewhere.

The flowers are extremely distinct as you can see in the pictures..... they have dark dots down one side of each petal.  To me they look like they could be some sort of Hypericum but that is just a guy feeling.  Checking my books I can't find the dots mentioned for any of that genus, and I can't for the life of me think of anything else except perhaps some sort of Hibbertia? 

Given how prolific they are this year I am somewhat hesitant to actually grow these plants in my garden, but the flowers are stunning when looked at up close, and extremely eye-catching as each plant stands to maybe 18 inches wide by 10 or 12 inches across (well the ones that are growing without competition and don't have to reach for light anyway).

Any ideas anyone?  Thanks in anticipation.

[WimB]

It looks like hypericum perforatum (St. John's Wort), it's a weed native to Europe.
It is a major problem in the US and Canada. I didn't know it was growing in Australia now too.

[Paul T]

There are so many of the St John's Wort in the books, yet none of them mention the dark dots.  H. perforatum mentions the pale spots on the leaves like in my photo, but no mention of the margins being darkly dotted on one side of each petal.  There are definitely some species of Hypericum that have naturalised here.  I never know which one is the actual medicinal one, but have always wondered (or are they all?).  I wonder whether it is a recent excapee, or whether the climatic conditions are just right for it to flourish this season around here?  It is spread all around Canberra as far as I can see, as I have seen it near all four "corners" of the city.

[WimB]

Hypericum perforatum has got these black spots on the petals. This is the real St.John's wort which has some medical uses. It seems to be the narow-leaved variety: Hypericum perforatum var. angustifolium.

links:
http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&state=nsw&s=&region=seh&card=H16
http://www.rbgsyd.nsw.gov.au/science/hot_science_topics/Ecology_of_Cumberland_Plain_Woodland/woodland_plants/hypericum_perforatum
http://www.fs.fed.us/database/feis/plants/forb/hypper/all.html

[Paul T]

Thanks WimB (Sorry, I don't know your actual name, just the ID).  Your help is greatly appreciated.

[WimB]

You're welcome.
For future reference  : my first name is Wim

[Paul T]

Thanks Wim.  Glad you've added a signature so we know.  It isn't always easy to work out whether someone's ID has any bearing on their actual name!!    Jumping to the conclusion that it does isn't always a good idea.  Nice to meet you!! (and Thanks again for your help!!)

Incidentally, I was away yesterday about an hour East of here and the Hypericum was seen regularly near the roads and out in the paddocks.  Large patches many metres across in places, seemingly randomly growing wherever the seed ends up.  Definitely well established outside of the immediate Canberra city limits, that is for sure.