Cenchrus purpurascens

Swamp Foxtail at Canberra Central, ACT

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Identification history

Cenchrus purpurascens

20 May 2016

michaelb

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User's notes

On the water's edge at Lake Burley Griffin, Yarramundi Reach.

7 comments

michaelb wrote:

18 May 2016

This appears to be an exotic Cenchrus species and has a very large tussock.
It looks different to the native Cenchrus purpurascens, in that the tussock is much larger and lush and it has the odd dropping flowerhead. It is also different from the exotic Cenchrus setaceus, which I found growing in a very dry location.

ACTBioSecurity wrote:

18 May 2016

Looks closer in id to African Fountain Grass (Cenchrus setaceus) than the native Swamp Foxtail (Cenchrus purpurascens) - based on length of flower spike (African Fountain Grass has a longer spike/raceme - but cannot rely on this alone). The way to tell is to pull out one of the spikelets from the flowerhead spike. If the bristles are straight and hairless then - Swamp Foxtail. If the bristles are feather like then African Fountain Grass. If African Fountain Grass - we need to remove asap, as this is a new and emerging weed in Canberra.

ACTBioSecurity wrote:

18 May 2016

Could I also please have a grid reference or reference point to help locate the site more easily?

michaelb wrote:

19 May 2016

Hi Parkie818
Thanks for your attention. The GPS points are -35.296372, 149.083347
It doesn't look like the native Cenchrus purpurascens, which we have growing down near Point Hut.
Cheers, Michael

michaelb wrote:

19 May 2016

PS please let me know what species you think it is.

ACTBioSecurity wrote:

20 May 2016

Hello Michael
Just visited the site. I checked the spikelets and they have straight bristles that are not feathery. So it is Swamp Foxtail (based on Harry Rose's Grasses of the Southern Tablelands field guide). One of the plants did have longer than usual flower spikes - making it look like African Fountain Grass. This did confuse me - but I checked the spikelets and definitely not feather like.
This look-a-like issue is why some Botanists think we should stop the sale of the native Swamp Foxtail because the potential for plant nurseries accidentally selling the invasive African Fountain Grass is high.
And once African Fountain Grass establishes it spreads very rapidly and has high control costs. Jenny Conolly, an ACT Government Weeds Officer, has been controlling an infestation for several years at Chapman, that started in a garden.

michaelb wrote:

21 May 2016

Hi Parkie818
I have confirmed it as Swamp Foxtail based on your advice. Thanks for the detailed explanation.

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