Friday, September 26, 2008

The tree of life....

So I was recently asked by an NGO that works on agricultural extension in developing countries, to write some articles for their website, about uses of the moringa tree. Actually, pretty much all this organization does is plant moringa trees and encourage people in third world countries- university students, farmers, agricultural extension workers, school kids, women with home gardens, people with a small plot of land, urban gardeners- to plant them and to make use of them. Moringa is a small tree or shrub, a cousin of the papaya family and a more distant cousin of the cabbage family, grown across the tropics for its edible leaves and fruits and a variety of auxiliary uses.

In Madagascar, planting Moringa trees (locally called añanambo in the West, feliky morongo in the south and añamorongo in the north) was something that I did a lot of. I gave a lot of presentations on the benefits of moringa, to a variety of different audiences (school kids, village associations, farmers, teenagers, and interested villagers), and I would try and work the benefits of moringa trees into many presentations that I would give, whether they were on agroforestry or nutrition. It got so that it was a bit of a running joke in my village, that I was crazy about the moringa tree. They didn't call me 'Mr. Moringa' but they might as well.

This is not a tree that is well known in the States, for the simple reason that it doesn't grow outside the tropics, and doesn't even grow well in the high altitude tropics. (In Madagascar, for example, it grows everywhere but the 'High Plateau.') I do have an uncle who tried to plant one in Texas, but it died; I'm thinking about trying to grow a few seedlings in a greenhouse.

The reason I was so enthusiastic about Moringa is because it has a wide variety of benefits and advantages- nutritional, economic, ecological and agricultural. It hasn't been the subject of a lot of scientific research, but what is known about it suggests that it could be planted and used much more widely across the tropics.

Moringa is actually the genus that includes about 12 different species, but the one of most interest as an agroforestry tree is Moringa oleifera. "Moringa" and equivalent terms ("morongy" in French, "marengo" in Spanish, 'malunggay' in Tagalog, "morongo" in the north of Mada) are derived from the Tamil "murunkakkai" as the tree is native to India. They can grow up to 8 m tall but are usually grown as tall shrubs or small trees, not more than about 3 m tall. They don't tolerate cold at all, but can flourish in a variety of rainfall regimes from rain forest to desert. (Moringa evolved as an oasis plant and is even now highly prized in dry regions of the tropics- southwest Madagascar, southeast India, the Sahel) where little else grows.

Moringa is most important as a source of green vegetables; you can eat the leaflets off the tree, as a leaf vegetable. It's a bit laborious to prepare since you need to strip the leaflets off their stalk, otherwise you end up with tough and inedible bits of stalk in your food. The taste is a bit like collard greens except stronger, and the texture is a little tougher; the leaves have a mustard-like scent which is pleasant when they're fresh but can get unpleasant if the leaves are left for days and begin to spoil. All in all, it's a pretty tasty vegetable, and can be cooked with rice, fish, shrimp, meat, millet porridge, and other things; often it works better if you mix it with other milder-tasting green vegetables, or add some onions to soften the flavor. The white flowers can be eaten as well, as can the fruits (which look something like long bean pods).

Green moringa leaves are probably the single most nutritious vegetable around. They have a good deal of protein, and much more calcium per unit weight than milk- about 200 grams of moringa leaves have all the calcium you need in a day. They are also good sources of vitamins and minerals.

Aside from that, moringa trees have some important auxiliary uses. The leaves contain a growth hormone (of the cytokinin group) which is soluble in alcohol but not in water. You can steep the pounded leaves in 80% ethanol to extract the cytokinin hormone- you could also use mroe dilute ethanol but then you need more solvent of course. The extract can be diluted with water as needed and used as a spray on leaves. Studies in Nicaragua suggest that it can improve the growth and yield of numerous vegetables and grains (corn, peanuts, onions, tomatoes, peppers) by 25-30%. It is, of course a _growth hormone_ that accelerates growth, and doesn't fuel growth; you need to support that growth with inputs of chemical or organic fertilizer.

I don't know of any scientific studies that have been done on whether moringa protects crops against insect damage. But I personally would guess that at the least, moringa leaves have strong anti-herbivore defenses of their own. In my experience I've never seen a moringa tree with significant leaf damage although that may be partially because the leaflets are tiny and the tree drops them when they are attacked. Moringa is closely related to the papaya family, and papaya leaves are widely used as a 'natural' insecticide in developing countries. The mustard oils which give moringa leaves their characteristic smell are known to be anti-herbivore compounds, and moringa leaves are known to contain alkaloids and flavonoids, a class of organic molecules often involved in plant defence. Moringa leaves are known to have nematicidal properties when used as a green manure, which suggests that they have some toxic secondary compounds.

Moringa also, interestingly, has 'extrafloral nectaries'- small nectar glands at the base of stalks. In some other trees (Acacias, most notably) these play a role in attracting predatory insects and ants that help defend the tree. I'm not sure if the ones in Moringa are involved in plant defense, attracting pollinators, or what. Plants in the cabbage family are known to actively 'solicit' predatory insects when they are under attack by herbivores- sort of like calling on the cavalry, I suppose. It's possible that Moringa can do the same thing. At some point it would be nice if someone did a study on it. Maybe after I finish with grad school I will try to do a small study along those lines myself, at least if fate brings me back to the tropics. But this is certainly too important a topic to go un-studied.

Moringa, finally, can be used as a water purification agent. I've tried it for this purpose before. I didn't drink much of the water, because I didn't really want to risk imbibing some nasty amoebas or Giardia (those are not pleasant ailments), but I did taste the water (which had come from a river) and it didn't make me sick. You can visibly see the junk in the water ( dissolved and suspended material) coagulate and sink to the bottom when you add powdered Moringa seed to the solution (just a couple seeds per liter). The explanation is apparently that the moringa seeds contain a protein attaches to negatively charged dirt particles and bacteria, and aggregates them into micelles, analogously to how soap helps clean off a surface. The technical term is a 'flocculant' protein....I just love that word.

There are other uses of Moringa too (green manure, nematicide, oilseed....there are apparently even farmers in Haiti who feed their pigs on sugar and moringa leaves. No kidding.) I will try and write about them some other time. But the take home message is that Moringa oleifera is a seriously under-utilized and under-studied plant that could play a big role in improved and sustainable rural development in the third world.


Anonymous said...

Hey! I'm in Madagascar and very interested in Morenga and how it can be used to improve the living conditions of the rural population. As you seem to have a lot of experience with that plant I would highly appreciate being able to talk to you. Could you please contact me or send me you contact details?

Warm regards,

Katharina_aver @

Anonymous said...

Where in Texas does you uncle live?
I live in north Texas and am going to try to grow a few Moringa trees here.