Ventenata dubia (blonde colored grass in distance) spreading across a hillside in Carbon County, MT.
Ventenata dubia is a grass that appears to be rapidly spreading throughout the northwestern United States and is gaining a proportionately growing degree of attention in conservation organizations and agencies. Native to Mediterranean Europe and Africa and surrounds, the grass seems to have gained a foothold the some years back but there has been a groundswell of interest in the last five or so years. I thought I’d share some thoughts and ideas from my perspective as a grazier.
We first became aware of this grass last summer, around the time when annual range grasses mature and senesce, demarcating them from their still-green perennial cousins. It’s likely the grass had been on this particular ranch for some time, but I was unaware of this as I just began managing yearling cattle there last Spring and am still learning these Montana plants. Since then, we have been learning all we can about the plant, and lucky for us, it appears agency, university, and conservation organizations are doing the same.
Unlike similar “noxious” grasses like Meduseahead (Taeniatherum caput-medusae) and Cheatgrass, which seem to grow more directly in response to management factors and which still offer cattle and wildlife some kind of meaningful forage prior to maturity, Ventenata does not seem to appeal to ruminants at all. Worse yet, it can spread in pastures that at a glance appear diverse and healthy.
The only time I have observed livestock grazing the Ventenata was in a moderate-density pasture (cattle were in there for about 4 days). Cattle did seem to graze the tips of the Ventenata a bit. Did this have to do with the density? Was that particular pasture size and grazing period just-so, incentivizing grazing of all species while still allowing enough selectivity that they could somehow utilize this bitter-tasting plant? Was it just a handful of steers who grazed the area I saw? And, or, did their grazing it have more to do with the mineral tub I placed nearby? If so, were they somehow able or incentivized to utilize the plant because of something in the mineral? Or was it sheer proximity?
Questions like these run through my mind all the time when it comes to this plant. Perhaps the most frustrating thing about Ventenata is that it seems to be able to grow in a wide range of soils. I have racked my brain trying to find clearly consistent patterns in where the grass proliferates, and so far I’ve only found a few:
- The grass will grow on east, south, and west slopes, but I’ve seen little to none on north slopes:
- The grass seems to grow taller and thicker this year, a year with less consistent rain and more heat, than last year, when we had a long but cool and slower growing season.
- Other than north slopes, the only places I’ve not seen the grass gain a foothold are areas that are extremely productive. These include irrigated hay meadows and lush areas along creeks and waterways that are grazed for short periods once or twice a year.
- The plant seems to propagate initially by small, independent stands of 1 - 3 feet circles that then grow and expand as these annuals reseed each year. The perimeter of the cover appears to iteratively expand until it simply fills in.
- Western wheat grass and a few tall-growing forbs like prairie coneflower, sweet clover, and alfalfa, are the only plants that seem to kinda-sorta grow through it. It’s hard to say if these are just the last plants to release their grip in an area, or if some—especially prairie coneflower—actually are doing well despite or even because of the Ventenata. What can these plants tell us about Ventenata?
Some of the following is likely answerable by further google searches and lit reviews, but for now, these are my primarily questions so far:
This grass seems to have an aggressive propagation strategy (germinate early in its own thatch, cool season annual that smothers other plants, short-lived abundant seed, little energy invested in developing root system) but what is its growth strategy? In other words, do areas monopolized by Ventenata simply persist as a monoculture of this plant indefinitely, or do other plants begin to propogate within it?
Does the hoof impact required to incorporate the Ventenata thatch simply exacerbate the problem by creating compaction? Or could this be a viable strategy for allowing other species to re-enter a stand of Ventenata?
Is Ventenata chemically allelopathic or simply structurally/mechanically limiting to other plants?
Ventenata seems to propagate successfully in its own thatch, yet I have seen it described as a plant that invades disturbed areas. What is it that makes this simultaneously true?
What do we know about how soil type, deficiencies, parent material, and bacterial:fungal ratio affect Ventenata?
Can the palatability of Ventenata be changed through some foliar application or fertilizer, thus causing cattle to want to graze it? One of the key challenges of this plant is that the only thing cattle seem to want to do with large monocultures of it is lie down in it, so the hoof impact on any given area is limited. Over time, cattle simply cease to interact with areas of the pasture altogether.
Post-senescence V. dubia with many species of flowering tall forbs successfully growing through. What will happen in this area next year?
We’re learning about this plant alongside everyone else, and invite discussion, curiosity, research interests, and so on as we explore how our management and decision-making can move the needle away from a Ventenata monoculture and towards a productive AND diverse grassland. For now, this is our approach:
1. Ad-hoc monitoring of changes in grassland and pasture composition via Solocator, a phone app that records the exact location and direction of a photograph, logs it on a map, records customized notes right on the photograph, and uploads them to your icloud account. I can’t say enough good things about this app. I didn’t use it last year, and really regret it. This year, in particular in July when the Ventenata had browned out but other grasses were green, I took many photos with this app and will use them to compare with the Ventenata spread next year.
Ideally we’d have test plots all over the place, but we’ve not had capacity to do this yet, and feel that Ventenata is obvious enough in its spread that basic and consistent photo monitoring will tell us a lot.
2. Grazing: we practice management-intensive holistic planned grazing with relatively short grazing periods and long recovery periods. This year we had fewer cattle at this ranch so some of the grazing periods were longer than usual, but in general cattle are not in any given cell or pasture for more than a few days during the early growing season up to a few weeks as things slow down, grasses mature, and we’re in pastures we’re not coming back to this year. The ranch seems to be responding positively to this.
We are also doing a few experimental things like fencing out areas of Ventenata altogether, and we did one experiment where we put about 350 6-weight steers on a 3/4 acre of Ventenata-dominant grass for 8 hours in somewhat wet conditions. The change in that stand of grass has been profound, but what will grow next year, and how can we get similar value with a more practical level of density?
3. Biological and chemical applications: This fall, we are hiring out to spray just a few acres with Rejuvra, the version of Esplanade herbicide licensed for rangeland use. I am not a fan of herbicides as a rule, but I am a proponent of rangeland health, experimentation, and openness to new ideas, so it seems worth a shot.
We’re also going to try an experimental application of hydrolyzed fish fertilizer and calcium, as advised by soil scientist Nicole Masters. I’m intending to do this both is a combination application and separately, to compare. The idea here is to address calcium deficiency in the soil and also feed the existing and emerging plants and microbes with the fish fertilizer. We don’t know if this will just grow more Ventenata, and we have not done soil tests yet to determine if this ranch is deficient in Calcium, but I understand it to be a common missing-link in soil health on many ranches in our area.
In the coming years, this plant will command countless resources in an attempt to understand its behavior and impact on rangeland in the US and perhaps beyond. Conference panels will convene, university research teams will require grant money to study it. Thousands of gallons of fuel and millions of gallons of water will be deployed in an effort to spray pre-emergent herbicides on the plant. In the near term, hundreds of thousands of acres (at least!) of rangeland and pasture will likely see a significant reduction in forage for livestock and wildlife alike. People will dismissively say that we should just wait it out, others will say we should treat it like an alien invasion. Beyond the specificities of this new invasive grass, I hope we can also maintain an investigative and observant spirit around the broader question of how humans make decisions and use resources in pursuit of their goals. Noxious weeds hold up a mirror to our species and our minds, and I think it’s worth taking the time to monitor ourselves alongside our pastures.
Holding rodear in mid-may on V. dubia. We were interested in the effect of animal impact on Ventenata thatch.