Isotoma fluviatilis subsp. australis

Swamp Isotome at Watson, ACT

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Identification history

	Isotoma fluviatilis subsp. australis	12 Jun 2023	Tapirlord
	Bacopa monnieri	12 Jun 2023	WalterEgo

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User's notes

Not really sure how to count abundance!

12 comments

abread111 wrote:

12 Jun 2023

Did you collect a sample? The species you suggest is new to the ACT and the CNM.

WalterEgo wrote:

12 Jun 2023

No, didn't take a sample. Proposed ID is a bit of a guess. Didn't look like the other options for freshwater plants I looked at on the CNM field guide...

JaneR wrote:

12 Jun 2023

I'm uncertain what this species is, but consider Bacopa monnieri highly unlikely. In fact I'm not sure why this species is on CNM list for Canberra and surrounds at all, as records (except one, odd one) are well to north of here on tablelands or coastal. PlantNet gives distribution as "north from Royal National Park". ALA has a photo (from I Naturalist) for the Snowy river region but this has not been verified.

Suggest you re-visit and record flower and fruits in the growing season. These are essential details to confirm species ID and to add a new species, not just to CNM but to the ACT. Vegetative characteristics aren't enough, I'm afraid.

WalterEgo wrote:

12 Jun 2023

Thanks, I'm now wondering if it is an isotoma... Will try to get back in spring/summer to check for flowers

Tapirlord wrote:

12 Jun 2023

Pretty sure this is isotoma.

JaneR wrote:

12 Jun 2023

me too, going for Isotoma fluviatilis. close up of leaves and stem would help.

natureguy wrote:

12 Jun 2023

Yes, agree looks like Isotoma leaves to me

waltraud wrote:

13 Jun 2023

I spotted Isotoma fluviatilus subsp. australis on Mt Majura's east slope in a moist environment but I haven't seen it growing in a flooded site. Sam, do you think this site is permanently under water?

JaneR wrote:

13 Jun 2023

A perspective on habitat: think variability.
Isotoma fluviatilis occurs on saturated soils, under shallow water and can persist despite prolonged inundation. Sites such as these on Mt Majura are ephemeral and/or seasonal, so water and moisture conditions vary enormously, driven by recent and longer-term weather. During the Millenium Drought, and hot dry conditions before bushfires, these creek lines were dry even hard soil, and devoid of amphibious plants like Isotoma. Coping with variable climate is what aquatic and wetland plants do, usually thanks to seeds.

waltraud wrote:

13 Jun 2023

Thanks for the very informative comments Jane.
Sam no need to further comment; thanks for the report.

natureguy wrote:

14 Jun 2023

Yes I'll back Jane up here, I've even seen it growing in lawn in the city, so definitely realistic.

Tapirlord wrote:

14 Jun 2023

Haha, I know the lawn ;)

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