Azolla Fern and Barnyard Grass Oh So Belong Together

05 Apr

Barnyard Grass and Azolla Fern a Match Made in Heaven

(or in a tropical rice paddy)


Question 1.  Guess what local invasive exotic grass is the main weed in rice.

Answer: Barnyard Grass, Echinochloa crus-galli, the English name reflecting its affinity for nitrogen-enriched soil.

Echino flowers

Barnyard Grass

Question 2. Guess what floating fern serves as a nitrogen-enriching rice paddy green manure.

Azolla Fern, Azolla filiculoides, A. pinnata

Azolla caroliniana 1

Azolla filiculoides on wet mud, by John Bradford. Highly magnified. This clump would be about 1/3 inch in diameter.

Question 3.   Guess what two rice-loving species hooked up in Riverbend Park near Jupiter, Florida.

Right!  Barnyard Grass, nitrogen-taker, and Azolla, nitrogen-maker, reunited like their good old Asian ricefield days.


Barnyard Grass in the Azolla soup. (Th light green is duckweed.)

Today a spine-tingling faculty meting displaced our usual Friday botanical investigations, but yesterday was great and green —a class field trip into the botanical wonderland known as Riverbend Park, where the Native Americans and U.S. Military met bitterly in 1838.

At the edge of the cypress swamp was a reddish crescent of floating Azolla Fern.   Barnyard grass was growing like a weed in the middle of the Azolla. Like old times!


The reddish region is almost solid Azolla filiculoides.  The  large plants, except those to the far distant right, are all Barnyard Grass.

Here is what “Bayer Crop Science” says abut Barnyard Grass vis-à-vis rice:

In rice E. crus-galli over time became the most dominant weed due to its similarity with rice that made it escape hand weeding frequently. Only the use of the selective herbicides offers reliable control. However, meanwhile several biotypes of barnyardgrass have developed resistance to various herbicides and modes of action.

And this is what the Azolla Foundation sez about Azolla and rice:

The ability of Azolla’s symbiont, Anabaena, to sequester atmospheric nitrogen has been used for thousands of years in the Far East, where Azolla is extensively grown in rice paddies to increase rice production by more than to 50%.

Although now widespread, Barnyard Grass is native to the Old World, not Florida. In Palm Beach County dwell two species of Azolla, which are the same two in China, Azolla pinnata and A. filiculoides.  Both are nice to rice.

1 Comment

Posted by on April 5, 2019 in Uncategorized


One response to “Azolla Fern and Barnyard Grass Oh So Belong Together

  1. theshrubqueen

    April 6, 2019 at 3:22 pm

    I have Barnyard Grass! but no rice!


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