Tag Archives: ragweed

Exploring and Speculating in the Snow

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Snow is a great boon to anyone trying to figure out what’s happening in the prairie during the winter. I’m just a casual observer, not a researcher of winter activity, but it’s definitely a topic of interest. A fresh snow fall provides a chance to look at tracks and try to interpret what’s happening.

Last week, I saw a couple interesting things in nearby snow-covered prairies. The first is something I’ve seen often before, which is evidence of the importance of western ragweed as a winter food. Ragweed plants sticking up above the snow are very commonly surrounded by bird tracks, and I saw lots of that at our family prairie last week.

Western ragweed (Ambrosia psilostachya) sticking out above the snow last week, showing the large nutritious seeds just sitting there ready to eat!
Bird tracks around western ragweed plants.

I know people tend to scoff at, or actively dislike ragweed, but it’s hard to dispute its value to wildlife. I understand those of you with severe allergies to ragweed pollen not being fans. Beyond that, though, it tends to get an undeserved bad rap from farmers/ranchers who mistakenly think it is aggressive and outcompetes grasses. The reverse is true – its populations expand when the grasses are weakened and shrink when grasses are strong.

Others dismiss it because it is a ‘weed’ and/or doesn’t have showy flowers to attract pollinators. Sure, it’s very common, and perpetual high abundance can be a sign of poor prairie management, but it’s also a native plant that plays an important role in grasslands. In addition to its ability to fill and temporarily hold space when the surrounding plant community is stressed, it’s impossible to dismiss the attractiveness of its seeds to wildlife. If you have any doubt, look for ragweed plants the next time you’re in a snowy prairie. Most likely, you’ll be able to follow tracks right to them!

Here, you can see both bird tracks and a few dropped seeds below the plants, where birds were pulling other seeds off to eat.

The second interesting thing I saw last week connects to another observation earlier this year. Back in April, I was walking through a recently burned area at Prairie Plains Resource Institute’s Gjerloff Prairie and found a pile of seeds I’m pretty sure were from marbleseed, aka false gromwell (Onosmodium molle). They might also have been from fringed puccoon (Lithospermum incisum) – the seeds of those two species are awfully similar.

Seeds at Gjerloff Prairie after a spring prescribed fire. I think these are from marbleseed, based on their size, though they might have been puccoon seeds too.

The way the seeds were gathered together made me think it was a seed cache, created by some kind of mouse the previous year. The fact that it was still there after the winter made me wonder if the mouse didn’t survive (or just didn’t find its cache). Either way, it was neat to see and fun to speculate about.

Last week, at our family’s prairie, after perusing the bird tracks around ragweed plants, I came across a mouse trail that led to a small area where it looked like the mouse had dug down to the ground. The tracks led pretty directly to the excavation site, making me think the mouse probably knew where it was going (as opposed to just wandering/foraging randomly).

Mouse tracks and an excavation.

Looking closely in the hole, I saw some seeds that looked just like the ones I discovered at Gjerloff Prairie back in April. Aha! More evidence. I know mice create seed caches, but I don’t know much about what kinds of seeds they might store, where they store them, or how good they are at finding them later. If anyone can enlighten me on this subject, I’d love to hear from you.

Here’s another photo from a little closer to the hole. I used Photoshop to open up the shadows and show the details inside the hole, and you can just barely see a few remaining seeds at the bottom. (Click on the image to see a closer view).

Just based on observation and speculation, it looks to me like some small mammal harvested and piled some marbleseed/puccoon seeds up – presumably in the early to mid summer when those seeds were ripe. (Based on a lot of years of seed harvesting, those seeds disappear from plants pretty quickly after they’re ripe – probably because of mice!) Then, on a sunny day after a snow, that same mammal (?) appears to have trekked across the snow and dug up the cache. Did it know exactly where it was? Based on the tracks, it sure looked that way to me – either that or it somehow smelled the seeds beneath the snow. One way or the other, I’m impressed.

As I said at the beginning of this post, I’m no expert on winter survival, especially by birds and small mammals. I do, though, enjoy trying to figure out what I can learn through observation, and snow is really helpful in that venture. Last week’s snow is melting fast now, but I’m hoping for a few more chances to explore later this winter. If anyone can help me interpret what I saw in these photos, I’d sure appreciate it!

Aggressive Weed or Opportunistic Plant? It’s Good to Know the Difference

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“Those weeds are really taking over my pasture!”

I cringe when I hear that sentence because it’s often a precursor to broadcast spraying of herbicide and the subsequent loss of most plant diversity in a prairie.  That’s really bad.  What’s most frustrating, however, is that the sentence is rarely true.

East Dahms pasture. Ragweed in degraded pasture.

The ragweed in this pasture is not acting aggressively.  It is filling spaces left open by grasses weakened by intensive grazing.  Within a year or two of this photo, this site was dominated by big bluestem.

It’s easy to understand how a landowner would look at a pasture that is visually dominated by ragweed, buffalo bur, snow-on-the-mountain, hoary vervain, or a number of other weedy plants and think those plants are aggressively pushing grasses out of the way.  In almost every case, however, the opposite is true.  Grasses are usually the bullies of the plant community, and only when they are suppressed by fire, grazing, or some other pressure do the “weeds” thrive.

There are a few weeds that can out bully grasses, of course.  Leafy spurge, crown vetch, and sericea lespedeza are good examples in the central United States.  They seem to be able to invade and spread regardless of the vigor of grasses and other competing plants.  Landowners should absolutely work to control those aggressive perennial species before they get a foothold across large areas.

Leafy spurge at The Nature Conservancy's Broken Kettle Grasslands in the northern Loess Hills of Iowa.

Leafy spurge can be a serious threat to prairies and should be dealt with quickly to prevent it from spreading throughout a site.

However, while there are some important exceptions, most pasture weeds are more opportunistic than aggressive.  Opportunistic plants don’t compete well with grasses or other perennial plants when those plants are at full strength, but can move quickly to fill spaces left between plants that are weakened by intensive grazing or drought.  Many opportunistic species are short-lived, and produce huge numbers of seeds, and those seeds sit in the soil waiting for a chance to germinate and grow.  When the tops of grasses are grazed off, the roots below shrink up as well, creating the perfect opportunity for seeds to germinate and new plants to establish.

The majority of those new plants will survive only as long as the vigor of the surrounding grasses remains low.  As those grasses recover, they regain their advantages, both above and below ground.  Annual plants may bloom and drop more seed, but those seeds have to wait until the grasses are weakened again before they can germinate and grow.  Perennial opportunistic plants might stick around a little longer, but most of those will also lose out to recovering grasses because of their poor competitive ability.

These "weedy" species are filling in while grasses recover from a grazing bout. In the meantime, the hoary vervain (purple) and upright coneflower (yellow) are providing important pollinator resources and great habitat for other species, including insects, reptiles, and birds like northern bobwhite.

These “weedy” species are filling in while grasses recover from a grazing bout. In the meantime, the hoary vervain (purple) and upright coneflower (yellow in foreground) are providing important pollinator resources and great habitat for other species, including insects, reptiles, and brood-rearing habitat for birds like northern bobwhite.

There’s an easy way to find out whether or not the “weeds” in a pasture are aggressive or opportunistic – build an exclosure or two to keep grazing out for a year or more.  If the grasses within those exclosures regain their vigor and dominance, you’ll know it was the grazing pressure that was creating opportunities for weeds.  If the weeds continue to dominate the area inside the exclosure for a couple years (assuming you’re not in the middle of a drought that is keeping those grasses down), you’ll know that either the grasses have been debilitated to the point of no return or the weeds are truly aggressive and in need of control.

Grazing exclosure at the Dahms Tract.

Even a small and simple exclosure can help determine whether weeds are suppressing grasses or just taking advantage of grasses already weakened by grazing.

As a final note, it’s important to understand that grazing hard enough to suppress grasses and allow weedy plants to flourish temporarily is not at a bad thing.  Ecologically, the habitat conditions created by those tall weedy plants are critically important for many wildlife species, including upland game birds.  Many important wildflowers also benefit from the opportunity to reproduce during short periods (a year or two) of weakened grasses.  As long as the grasses are allowed to recover before they are intensively grazed again, they’ll be fine, and the wildlife, pollinators, and plant diversity of your prairie will all benefit from the temporary reprieve from grass dominance.  Shifting intensive grazing and subsequent rest periods around a large prairie, especially when those grazing/rest periods are a couple months long or longer, seems to be a great strategy for maintaining prairie health.

Opportunistic plants suffer from a public relations crisis.  While they are scorned by most people, these valuable plants are doing exactly what they’re supposed to do.  They are the temp workers of the plant community – the substitute teachers, backup quarterbacks, and house sitters that keep prairies humming along when dominant grasses are on sick leave.  By filling spaces between temporarily shrunken grass plants, opportunistic plants can help prevent the truly aggressive weeds from easily gaining a foothold.  They can also provide much needed habitat for wildlife and pollinators.  Ragweed, hoary vervain, and buffalo bur aren’t the villains of the story at all – they’re the heroes!  We just have to get used to seeing them that way.