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  • From: "Lawrence F. London, Jr." <lflj@bellsouth.net>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: [permaculture] Duckweed and its uses.
  • Date: Fri, 20 Nov 2009 00:17:03 -0500


Anyone here interested in duckweed and its many uses?

Here's some basic information on it:

http://www.mobot.org/jwcross/duckweed/duckweed.htm
The family of duckweeds (botanically, the Lemnaceae) are the smallest flowering plants. These plants grow floating in still or slow-moving fresh water around the globe, except in the coldest regions. The growth of these high-protein plants can be extremely rapid. Lemna is one of the best known of this group and has been the subject of much research.

Researchers are using these plants to study basic plant development, plant biochemistry, photosynthesis, the toxicity of hazardous substances, and much more. Genetic engineers are cloning duckweed genes and modifying duckweeds to inexpensively produce pharmaceuticals. Environmental scientists are using duckweeds to remove unwanted substances from water. Aquaculturalists find them an inexpensive feed source for fish farming.

Botanical Facts
http://www.mobot.org/jwcross/duckweed/duckweed.htm

Wikipedia
http://en.wikipedia.org/wiki/Lemnaoideae
Lemnaoideae
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Lemnaoideae
Close up of two different duckweeds:
Spirodela polyrrhiza and Wolffia globosa.
The very tiny Wolffia plants are under 2 mm long
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
Order: Alismatales
Family: Araceae
Subfamily: Lemnoideae
Genus

* Spirodela
* Landoltia
* Lemna
* Wolffiella
* Wolffia

Lemnaceae is a family of flowering plants, also known as the duckweed family, as it contains the duckweeds or water lentils. Since duckweeds are now considered to be a branch of the arum or aroid family (Araceae)[citation needed], the name 'Lemnaceae' is rapidly falling out of use among taxonomists[citation needed], who treat it as a subfamily called Lemnoideae[citation needed].

These plants are very simple, lacking an obvious stem or leaves. They consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface, with or without simple rootlets. The plants have become highly reduced from their relatives in Araceae. Reproduction is mostly by budding, but occasionally a flower consisting of two stamens and a pistil is produced (some view the 'flower' as a pseudanthium, or reduced inflorescence, with three unisexual flowers, derived from the spadix in Araceae). The fruit is a utricle, a sac containing air and a seed designed to float. The flower of the Wolffia is the smallest flower in the world; measuring in at a size of 0.3 mm long.[1]

Duckweed is an important food source for waterfowl and are eaten by humans in some parts of Southeast Asia (as khai-nam). Some duckweeds are used in freshwater aquariums and ponds where they may spread rapidly and, in a large pond, may be difficult to eradicate once established. The plants can provide nitrate removal (if cropped) and cover for fry. The plants are used as shelter by pond water species, such as bullfrogs and bluegills. The duckweeds are important in the process of bioremediation because they grow rapidly, absorbing excess mineral nutrients, particularly nitrogen and phosphates. A cover of duckweeds will reduce evaporation of water compared to a clear surface.

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In the context of food cropping in Vanatu I submitted this idea to a friend
in Sanet:

I would suggest biointensive, no-till, permanent, mulched (compost and
cover/companion crops)
raised beds with drainage ditches cycling nutrient rich water from gardens to catchment posds growing duckweed. The duckweed will extract 85% of all nutrients in the water, are high protein (as high as soy), low fiber and can be used as human and livestock food or as a nitrogen-rich soil amendment (read: fertilzer) to put back onto the crop beds. Duckweed can be used to purify sewage and manure lagoons, producing regularly harvestable duckweed as a farm input. When duckweed is dried its natural state is granular, perfect for storage and application on gardens.


A more robust livestock component of their subsistence farming system would be a good thing. Then you have the nutrients and microbes to make enhanced compost to greatly enhance their growing beds. Cover crops could be really beneficial. Permanent notil biointensive raised beds are almost self-maintaining microbe-wise and almost nutrient-wise too. Their food crop production could be usignificantly upgraded through the addition of manure to their compost. Keep the gardens in one location permanently; keep livestock nearby, make thee compost there also. Save labor for manicuring and maintaining fertility in the beds. Just a thought. Grow crops on slop[es that are suited to that terrain and others on more level ground; cycle water borne nutrients from one garden to another with ditches. Overflow can go to duckweed lagoons.




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