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"Take Two"
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November 20, 2001


When I travel through the desert, and by that I mean the area beyond the spread of Las Vegas development, I see plants. Now, these are not the big maple trees I saw during my many years in upstate New York and in New England. So what? Many remarkable plants - the Joshua trees, mesquites, barrel cacti, yuccas, and tons of spring and fall flowers - have established a kind of harmony with this harsh environment.

What we find in the desert is not a dense forest of broad leaves, nor a rippling sea of tall grasses, but rather, a stately parade of individuals growing in an unforgiving, dry terrain.

Given that there's so little nourishment available for plants here in the Mojave, it probably is best that they're so sparsely distributed. So maybe we think of them all out there as rugged individuals. That is what they look like. But are they? Really?

"Sharing" isn't a term we throw around much when we’re talking about horticulture. Still, what if each of those plants is not surviving because it's the toughest, but rather because it has created good relationships with other forms of life - maybe even forms we can't see with our naked eyes?

This may sound surprising, and you might think that it's quite unlikely, but more and more, scientists are not thinking of plants as living in some kind of solitary splendor. Rather, there's a developing vision of plants coexisting with certain microbes in the soil. Having relationships with bacteria and fungi results in the plants being able to obtain bigger and better supplies of water and nutrients. In fact, without these interactions among the various organisms, our beautiful desert could become totally barren - just a lifeless wasteland.

Bear with me for a second while I explain - this is science but it's not awfully complicated. Specialized bacteria have the ability to take nitrogen out of the air and transform it into compounds that leguminous plants then use to make proteins. The very proteins that we need for life. It's through these rhizobacteria most of the usable nitrogen on our planet gets fixed. A lot of exquisite desert plants have special interactions with these nitrogen-fixing bacteria. Mesquite, acacia, cassia, indigo, bird of paradise and many others are legumes. They permit selected bacteria to live in nodules on their roots, with the result that they have first dibs on those essential nitrogen compounds.

In addition to these important associations with bacteria, it turns out that maybe 90% of all the plants on earth have some kind of an arrangement with fungi. You know, molds, mushrooms - fungus. There are a couple of groups of essential fungi that produce long threads that go through the soil. These threads pull critical nutrients from the soil and make them accessible to the plants, which in turn use them for growth.

The plant roots, on the other hand, produce compounds that these microbes in the soil need for their own life and development. It's a mutually beneficial arrangement that’s called mycorrhizae, and in the desert, it really is a matter of life and death for those plants we admire so much.

What's even more startling is the fact that these fungi can help plants to interact with each other. Different plants have different needs and resources, and they use those threads that the fungi produce as highways to deliver assets from one plant to the other. You might say they are sharing the wealth so that all are helped. It could be, too that our own landscape plants rely on these same types of affiliations for their well-being.

There are some sites on the Internet where you can buy spores of certain fungi to get the associations started, but this is not a "one size fits all" kind of situation. Plants and fungi are selective about who they are going to form relationships with. Not all fungi will benefit all plants, so it might be just as well to use a little of the native soil and count on promoting the population of fungal spores that already exists there.

If we are going to keep our native plants alive and perhaps benefit our own landscapes, it's important that we don’t break these associations by killing off the necessary microbes. Pesticides can cause real damage to them. If you must use a fungicide or a weed killer in your landscape, please, be very careful. Read the label and make sure that you are using the right product for your problem. Call the Cooperative Extension master gardener hotline before applying any chemical that might kill off critical bacteria or fungi. The number there is 257-5555.

For KNPR's Desert Bloom, this is Dr. Angela O'Callaghan of the University of Nevada Cooperative Extension. Take care.

See discussion rules.


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