gwl-g@lists.ibiblio.org
Subject: gardenwriters-on-gardening
List archive
- From: "Lon J. Rombough" <lonrom@hevanet.com>
- To: Gardenwriters on Gardening <gwl-g@lists.ibiblio.org>
- Subject: Re: [gwl-g] Fairy moss and duck weed
- Date: Fri, 28 May 2004 16:23:52 -0700
Title: Re: [gwl-g] Fairy moss and duck weed Duckweed is a real nitrogen hog. When there are excess nutrients in the water, it goes nuts. You can actually see the plants divide. We have a prime example of that. Our neighbor has a pond full of planted trout, but he keeps them at an unnaturally high density, way more fish than a natural pond could sustain. To do that, he has to feed them like crazy, which means that the water is full of nutrients. Since his pond drains into ours, we get all the nutrients and the duckweed blooms constantly. We have ducks, nutria and many other wildlife that come to "graze" on the duckweed, and it still makes a solid carpet all summer. However, if the nutrients stop, the duckweed "bloom" will peter out quickly. The Azola, on the other hand, can grow with very low levels of nutrients. However, it needs higher temperatures to be grow well.
So what is probably happening is that the duckweed takes off early when it's cool, then when the temperatures get warm enough for the azola to do well, it out-competes the duckweed, removing nutrients from the water so well that the duckweed slows or stops and dies back. If anything, much of the duckweed might die and decay, feeding the azola even more.
When cool weather comes, the azola slows and fall rain (or other things) bring more nutrients into the water to get the duckweed going a little again, at least enough to hold it over winter until spring.
Incidently, fish don't eat duckweed, but as the name implies, ducks do, Along with other waterfowl and the aforementioned nutria. And when they eat a lot, they poop, which just puts nutrients back in the water, though in a form other water life can eat.
-Lon Rombough
I have a question for a knowledgeable pond person
I have a tiny pond (my lily puddle), and I'm one of those weird people
who actually likes the green look. I cultivate duck weed and azola.
The duck weed is hardy here and overwinters outdoors. The azola isn't,
but usually a bit clings to plants I bring in and reestablishes itself
outside when I take the plants back out.
Since the duck weed is already in residence outdoors, it is usually
growing well before the azola comes to visit. But in most years within a
few weeks the azola completely takes over, banishing the duck weed to
wherever it is that duck weed goes. Right now I have a cover of duck weed
with maybe a couple dozen dots of azola; I expect it to be all azola by
mid-July. Not that I mind. Azola is a more interesting plant.
But why does this happen? My first thought was that the fish like to eat
the duck weed but not the azola. On further consideration, though, that
doesn't make sense. If that were the case, in years when I don't have
azola, the fish would presumably eat all the duck weed faster than it
could reproduce, right? And I'd be left with nothing but boring, clear
water and the bottle caps on the bottom.
-
[gwl-g] Fairy moss and duck weed,
Duane Campbell, 05/28/2004
- Re: [gwl-g] Fairy moss and duck weed, Lon J. Rombough, 05/28/2004
Archive powered by MHonArc 2.6.24.