Roger Rosentreter is a botanist for the Bureau of Land Management and an author and teacher. This interview was conducted for the OUTDOOR IDAHO program “War of the Weeds.”

Why does Idaho have a weed problem?
Idaho has a major weed problem partly because the climate in southern Idaho is so similar to parts of the Mediterranean climate where these weeds have evolved.

It’s a very different ecological world with these new weed species.

Whenever you plow up the ground, you can cause damage; whenever you dig it up, whenever you scrape it with your boot or cause any soil surface damage, you make that site favorable for weeds. You prepare the seed bed for weeds.

Sometimes there’s an attitude that you can disturb soil and not worry about it, that Mother Nature will heal it. I think that worked before we had weeds. A lot of the ecological principles have kind of changed. Now that we have cheat grass – a very aggressive annual grass – things have changed. It’s a very different ecological world with these new weed species, and I think it’s doing to continue to keep changing.

What are noxious weeds?
The definition of “weed” can be kind of broad, but when it comes to the group of weeds that we call “noxious” weeds, they are particular plants that are very aggressive. They increase quickly; they are difficult to eradicate, and there is general acceptance that these are undesirable plants for the landscape.

They often displace or replace desirable species that are more edible to livestock, to wildlife, to insects in the food web; and these plants often contain toxic chemicals or coarse textures, and they decrease the use of that land for commercial or recreational uses.

Idaho is going to look like some of the deserts in the Middle East.

Are there things we can do?
One of the long term solutions to weed management is to minimize the amount of disturbance. So, when you build a house, try to minimize the amount of soil that is disturbed and try to take care of disturbed sites. If a weed seed gets there before a perennial grass seed gets there, you are going to have a site that is dominated by weeds. Once a weed gets there, producing lots of seeds, they can colonize and control that site for many years to come.

If you control a site with herbicides, then you need to go back and plant something. Otherwise you get in this endless cycle of “herbiciding” every year. It’s not very satisfying to go spray the same site year after year; you haven’t accomplished anything. And so you really need a two-pronged approach. You really need to replant some sort of perennial plant afterwards, or change management of the area and not disturb it so much. Otherwise, you are just going to be repeatedly spraying the same site again and again and not really getting anywhere.

If you drive an off-road vehicle, you should clean it between use. You should really be careful about driving a vehicle like that in different parts of Idaho or different parts of the country. If you go on a trip in California where they have a lot more weeds than we do, and then drive your vehicle on a bumpy back road in Idaho, you could be spreading weeds that are new to Idaho. Make sure you clean the underside of your vehicle.

I am often disgusted by your typical 4-wheel drive or sport utility car advertisement, where they are throwing mud around as if that is a good thing to do. I think society needs to have some values and say that this is a bad thing to do. If you want to drive that 4-wheel drive, you ought to do that on a road or on a trail, and there should be social pressure to not be off trail and not damage things.

Even recreationists who roll out their insulite pad or camping bag, and go on a trip to New Zealand. When they come home, they can bring seeds with them that can be very damaging.

Once they burn, they are going to burn twice as fast as they did the first time.

What will Idaho look like in the future?
I’m sorry to say that in the future, we will go from grass species that we think are pretty bad to worse species that will have chemical toxins that inhibit the eating of them. The Middle East has a similar climate as parts of Idaho, and if you want to see what some of arid Idaho is going to look like, it is going to look a lot like some of the deserts there.

In another ten years I suspect you will have a lot less shrubs, more weedy grasses and you’ll start to have the weedy grasses replaced by other perennial weeds, which are less palatable and more noxious.

So it’s a very risky environment when you have vegetation that is dominated by annuals. The long term solution is to try to establish perennial plants and desirable grasses, whether they are native or introduced and have that dominating the landscape, so it’s a more predictable environment and it’s less flammable.

What about the Boise foothills?
When I came to Boise twenty-five years ago, burr buttercup, a little weed, was not present in the Boise foothills, and now it’s very common. So just in our lifetime we can see a drastic change in the structure of the vegetation, going from a mix shrubs and grassland with open spaces between the grasslands that were covered by mosses, to a more continuous kind of weedy grasses and that presents a much more flammable environment.

Once you have a more flammable environment and a dry climate, then you are going to tend to have more fires, and then those fires will burn more of that sage brush.

The Boise foothills, even twenty five years ago, had a much more gray-green appearance. In some places, it was dominated by a dark green bitterbrush. very palatable to deer and elk. These plants have been decreased because of fire in the foothills. And it’s replaced by a sort of straw, light tan-colored, straw-colored grass. And these grasses are very different in their structure than the original vegetation. Generally speaking, the colors have gone from a gray-green or a dark green to a straw color.

When it burns and becomes all grass, it becomes more arid. Some people refer to this as desert-ification. It becomes a drier environment because of the structure of the vegetation and the interaction with the weather conditions.

Now these valleys are just tinder boxes waiting to burn. And once they burn, they are going to burn twice as fast as they did the first time.

Can we meet the challenge?
With weeds it’s a real interesting, yet challenging adventure. Weeds don’t know boundaries. They don’t understand private property, public property, or fence lines. So you have to kind of mend any fences with your neighbors and set down differences of opinion and work on a united front to try and control weeds in a given area.

I look at how agencies, individuals and counties approach weeds today, compared to twenty years ago. I think we are much more enlightened about what is really going to work; we are more united. We give each other support, even though it is a very overwhelming problem.