Three Sisters... my new word: "allelopathy"

Yesterday I read a good article in the Aug/Sep issue of Organic Gardening.  The article focused on the "Three Sisters" method of gardening and it mentioned some new stuff I had never heard before.  Here goes:

"Most gardeners have heard of 'three sisters,' three food plants traditionally grown together by native Americans, and supposed reasons why the crop combination works:  The corn acts as a pole for climbing beans, the beans fix nitrogen, thereby providing an important plant nutrient; and the squash's broad leaves shade out the weeds."

Moving on, "As it turns out, squash plants do suppress weeds, but in addition to blocking the sun with their large leaves, they also take on the weeds through and altogether more sophisticated mechanism:  allelopathy.

"Allelopathy is 'chemical warfare between plants,' says Stephen Duke, Ph.D., research leader a the USDA's Natural Products Utilization Research Unit.  Allelopathy occurs when plants produce natural chemicals, known as allelochemicals, that inhibit growth of competing species."

Some more points I got from reading the entire article:

The phenomenon of allelopathy was not understood until about a century ago.  Duke explained that "juglone" found in black walnut is very toxic to other plants (I've heard about this before).

"Squash can inhibit surrounding weed growth through their roots and through leaf litter that has fallen to the ground or from dead, decaying plants.  The chemicals inhibit weeds more than they impact crop plants."

A sad point is that most plants have had allelopathy bred out of them to increase yield.  As a result, Duke says, "Weeds tend to be more allelopathic than crops [because] we haven't tinkered with them."

Types of crops that can be allelopathic are a certain kind of rice, "beets, corn, wheat, oats, peas, buckwheat, millet, barley, rye and cucumber.  Additionally, several species of sage have been shown to inhibit cucumbers and oats; sunflowers impact wheat; and wormwood suppresses beans, fennel and peas.".

Mulches made from allelopathic plants can help retard weed growth.  The allelochemiclas they release break down quickly, so they won't harm the next crop you plant in that space.  Make sure that, when applying allelopathic mulches to crops, the crop plant is well established before applying the mulch.

I have heard about other crop combinations that can be good or bad (I can't think of any specific ones right now though).

The last sentence in this articles says, "Imagine a day when 'applying herbicide' means spraying and aqueous mixture of a strongly allelopathic plant!"

I just wanted to share that with everyone.  The article is entitled "Weed Whacked" and it was written by Jill Richardson.

I don't know how I missed this before. Great article, Windmere, thanks for posting about it!

Thank you for the comment mollyhespra.  These types of scientific facts are fascinating to me.  Who would have thunk?

that was very interesting. would like to read more about it
thank you