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Amaranthus tricolor photo
Amaranthus tricolor via

For a while, I’ve been thinking about doing a Desert Bloom segment on weeds, just weeds in general, but there’s so much to talk about with these plants that I figured it would be better to narrow my focus. After all, even the definition of weed has a lot of variants.

I came up with a few, and I’m not talking about cannabis.

A weed could just be any plant we didn’t put in the ground deliberately, but that would exclude things like native plants, which are certainly not weeds.

It could be a situation where something we did plant in one year comes up the following year. I’ve had to pull out tomatoes that were volunteers from the previous year. In the mid west, corn and soybeans are often grown sequentially, year after year. As you might imagine, the biggest weed in corn would be soy, and likewise, the biggest weed in soy is corn! We wouldn’t think of any of those crops as weeds, though.

Of course, some plants are weeds, at least to most of us. Russian thistle, tumbleweed, comes to mind. No doubt, some person, somewhere, has developed a use for it, but I haven’t heard. I can’t include dandelion in this “usually weeds” category, since people do make dandelion wine and desert tortoises apparently like it.

Then, I must mention the weeds that many people don’t consider to be weeds at all. In much of American agriculture, red root pigweed is an enemy that must be controlled. Many of us call its near relations “amaranth”. A lot of wonderful ornamental and edible plants are amaranth, and you can buy seed for any of them, except red root pigweed, which is also edible. In fact, a colleague and I did some web searching, and couldn’t find any amaranth that wasn’t edible!

Purslane’s another example. Supposedly it behaves like an annual in our USDA growing zone. It’s invaded parts of my garden and now I’m locked in a battle with it. I looked it up on the web and found that of the first ten entries on purslane, nine were concerning its role as a food and a medicinal plant. This made me feel deeply moved, but I continued to pull it out of my walkway. This is a close cousin of the ornamental portulaca, sometimes called “moss rose”. They’re both the same species, but the weedy one doesn’t have the lovely floral display of the other.

If you’re not careful, you might find some sources calling purslane “spurge”. It’s not even distantly related. Spurge is not edible; don’t confuse them. Purslane has its own family! Purslane’s leaves are very succulent and prostrate spurge is definitely not. Even as I’m trying to kill the purslane, I’m also eating some. It’s not bad, if somewhat slimy. It’ll never be my favorite vegetable, but if I were hungry enough, you can bet I’d eat it. A lot of people do — all over the world. The common wisdom was that it originated in Eurasia, but apparently Native Americans were eating it long before Columbus.

It’s complicated, this problematic plant information.

And I haven’t mentioned all the things we do to control weeds. Americans spend huge amounts of money on herbicides. And the more herbicides we apply, the more likely it is that weeds will become resistant to them. The best control is to catch the problem as soon as you see that plant poking its way out of the soil. You get more and more vigorous if the problem is tenacious. Some are so hard to control, especially if they’ve been in the ground for a long while, and worst of all, if they’re vines. In these cases, even herbicides might not be effective, and it really does come down to removing by hand.

What I haven’t talked about is the classification of noxious weeds. This is a legal term for plants that are so potentially destructive — to human health, to agriculture, to the wild environment, to commerce — that we just shouldn’t have them around. This category deserves its own Desert Bloom. And at some point, it’ll get one.

Speaking of which, for KNPR’s Desert Bloom, this is Dr. Angela O’Callaghan, associate professor and Social Horticulture Specialist, Emerita, of the University of Nevada Reno. Yes, I’m retired from teaching, but definitely not retired from Desert Bloom.