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  Aroid versus Aroid
From: Theodore Held <oppenhauser2001 at gmail.com> on 2010.01.19 at 18:36:01(20491)
Greetings All,

I cultivated a nice water surface with a pure stand of the floating
duckweed species Spirodela polyrhiza. I find that this plant is much
less of a nuisance than its relative, Lemna minor, while still
presenting sufficient shade to inhibit underwater hair algae.

By and by, however, a fragment of Lemna minor found its way in and the
new species was soon was pulling its own. Part of my practice is to
sweep away 5% or 10% of the duckweed cover every few days so that the
fish can be fed with dry food. Natural growth renews the surface cover
again quickly. Rather than providing a neutral growing space for the
two species in my set up, however, I found that after a few months I
had a nearly pure crop of Lemna and hardly any Spirodela remaining.

Here are my questions:

First, has anyone else had this same experience? If so, did the
Spirodela polyrhiza end up with the short end of the stick?

Second, what do people suppose might happen in a similar competition
with Lemna minor and some Wolffia species? Is the competition fostered
by smaller leaf size, for example? Alternately, is it just my
condition that favors Lemna and that other conditions might favor

Third, do others have any experiences with or knowledge of
aroid-on-aroid competition? If so, what has been the outcome?

Keeping with the duckweed theme, one last item the list might find
interesting is the fact that Lemna minor may be the only natural
growth of aroids that can be easily distinguished and identified while
flying in a commercial airliner at 10,000 feet. The bright green ponds
of Florida are unmistakable. The only other aroid candidate that I can
think of for high altitude identification might be fields of
commercial taro, or similar crops. Does anyone else know of a
candidate aroid?

Ted Held

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