Martin Crawford, a prolific author on agroforestry and
director of the Agroforestry Research Trust (founded
by James Lovelock, co-author of the "Gaia hypothesis)
in England has written an 87-page booklet (ISBN
1-874275-25-4) called "Nitrogen-Fixing Plants for
Temperate Climates." The advertisment for the booklet
notes that "most people only know of the legumes as
nitrogen fixers; however, there are several other
plant groups which do so, notably the so-called
actinorhizal plants (including alders, Elaeagnus, sea
buckthorn), which are mostly of temperate origin and
better suited to cool temperate climates." Crawford's
book on temperate climate nitrogen fixers is dated
1995 and is advertised on the Agroforestry Research
Nitrogen-fixing can be a very recondite and forbidding
subject when presented by the usual gatherings of soil
specialists and microbiologists. I am not aware of
many "chatty" and user-friendly presentations of this
subject in print, so Crawford's could prove welcome.
Here in New Orleans, the Louisiana Nursery and
Landscape Association and the Louisiana Cooperative
Extension Service have issued "Tree Ratings for the
New Orleans Area." In this report, they relegate two
popular nitrogen-fixing trees--the Mimosa (Albizzia
julibrissin) and the Black Locust (Robinia
pseudoacacia) to the very bottom of the list with a
"Rating 4 (Poor)" category. In their experience,
these two trees are problematic in New Orleans for one
or more of the following 5 reasons: poor life
expectancy, poor aesthetic qualities, susceptibility
to insect and disease problems, lack of adaptability
to climate and urban conditions, and amount of
maintenance required. They are no more specific than
this, but they
dislike these two trees for our ecology and climate.
I'm wondering if we would do better in Southern
Louisiana with shrub-like nitrogen-fixing plants
rather than nitrogen-fixing trees. The Amorpha
fruitcosa or "false indigo" is a likely prospect.
Any comments would be appreciated.
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