Acaena has about 100 species, mostly in temperate regions. The most widespread species in Australia (and the UK for that matter) is probably Acaena novae-zealandiae, called Bidgee-widgee in my home State of Victoria. The common name of many Acaena species often includes the word ‘burr’ – e.g. Sheep’s Burr – an indication of why this genus includes so many weedy species.
Acaena ovalifolia is robust and useful rockery ground cover in London. Here it is in Kew Gardens' Rock Garden enjoying the first freezing fog of our winter. It’s native to South America, from the southern tip up to Columbia and including a UK overseas territory, the Falkland Islands. While it hasn't made it to Australia as a garden escape it is rather vigorous in the UK.
Not a surprise for a plant that is described as flowering freely, producing abundant (burry) fruit and fast growing.
According to the Garden Flora of Northern Ireland, this and a few related species have become naturalised in Northern Irish forestry plantations and woodlands, sometimes to nuisance levels. In fact it is illegal to plant any Acaena in the wild in Northern Ireland.
This particular species is only grown occasionally in gardens and according to the Online Atlas of the British and Irish Flora it was only first recorded ‘from the wild in Britain’ in 1951, from western Cornwall.
There are other species in cultivation here in the UK, including Acaena microphylla, winner of an RHS Award of Garden Merit (that means it's a good one to grow). The Royal Horticultural Society describe the fruits of this species as 'attractive burr-like'. Interestingly they give the common name as New Zealand Bur, rather than New Zealand Burr, or for that matter the New Zealand Bidgee-widgee, or as they seem to say in the country of origin, Bidibid.
And Acaena wasn't the only plant at Kew Gardens to 'benefit' from a little frostiness. Take a look at these shrubs, fruits, flowers and stems, taken early in the morning as the mercury drifted from minus two to zero a few days ago.