The BSBI Atlas 2020 plantatlas2020.org/atlas/2cd4p9... suggests a recent decline for currently unknown reasons. Speculation on the possible causes range from changes in management and eutrophication to changes in the hydrological flow of water bodies. - ThreadSky

astridbiddle.bsky.social • 34 days ago

The BSBI Atlas 2020 https://plantatlas2020.org/atlas/2cd4p9h.vzz suggests a recent decline for currently unknown reasons. Speculation on the possible causes range from changes in management and eutrophication to changes in the hydrological flow of water bodies.

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rogerhorton.bsky.social•34 days ago

That Atals2020 distribution map is a great illustration of the differnce between the overview/hectads and zoomable/tetrads versions. Latter gives a much clearer view of distribution related to habitat!

astridbiddle.bsky.social•34 days ago

It can sometimes be planted as an ornamental. This might be the case at the farm pond near Little Gaddesden (shown in May) where I went for my walk yesterday. It reaches from edge-to-edge, along with Reed Sweet-grass (Glyceria maxima).

bramblebotanist.bsky.social•34 days ago

In NL it also grows as part of floating raft communities on wider ditches and slow watercourses; a habitat we’re pretty much entirely missing in GB due to tidiness and boat traffic

astridbiddle.bsky.social•34 days ago

I've not seen the NL rafts. Do these differ from a floating sedge edge?

bramblebotanist.bsky.social•34 days ago

Floating sedge edge too. Rafts more herbaceous: Glyceria, Mentha aquatica, Cicuta virosa, Lycopus europaeus, Rumex hydrolapathum

astridbiddle.bsky.social•34 days ago

Nice!

jimhorsfall.bsky.social•34 days ago

I have a site with broad fringes of floating Typha beds, but generally species poor. It seems to occur only where the reedbeds are in the lee of willows (not much wave action). There is a sharp distinction in community between rooted Common Reed and floating Reedmace.

astridbiddle.bsky.social•34 days ago

What surprised me was the size of the root, ca 30 cm. In Herts, I usually recorded it as a bankside plant, present in single numbers. However, in permanently flooded habitats, it survives using an aerenchymatous root system (allows gas exchange). A helophyte with a submerged over-wintering rhizome.

astridbiddle.bsky.social•34 days ago

Where I've seen it increase on rivers is where there has been more recent build-up of silt, again with fast-colonising Glyceria maxima holding the wetter areas. The seeds of R. hydrolapathum need drier ground to germinate.
Dredging & deepening creates abrupt transitions, limiting its opportunities.

jimhorsfall.bsky.social•34 days ago

My limited experience of trying to grow this ex situ is that it is extremely palatable to slugs and snails (at least when young). Could another factor be lack of recruitment of new plants due to herbivory? (Also older plants don't live for ever, so needs some replacement over time).

astridbiddle.bsky.social•34 days ago

Perhaps catching vegetative stems of Dock too.

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