ARBORETUM NEWS (NATURALISTSNOTES)

Curtis Prairie Walk – Naturalists’ Notes

SUNDAY, JUNE 22, 2014

Things change. Over the past several years, I have boasted about how well prairie plants can handle the dry, hot weather. This summer I’m impressed how they are handling months of cloudy and wet conditions. We couldn’t walk on many of the paths through Curtis Prairie without getting our feet wet. This itself was an interesting reminder and lesson for all of us. We often don’t focus on the wet areas in the prairie and on the water that flows through it. Today, it was impossible not to pay attention to that. The topography reminded me of trips to the Everglades. Instead of cypress domes, we have willow thickets in our low, watery places. And, rather than alligators, we are likely to find large populations of chorus frogs in our watery spots. So, we circled and backtracked along the drier outer edges of Curtis Prairie.

As I looked at my notes over the years I see a positive change – we couldn’t find any gypsy moth caterpillars pupae shells on the bark of the oaks along the edge of the prairie along Arboretum Drive. On the other hand, although we saw much more of the host plant for monarch butterflies, common milkweed (Asclepias syriaca), we saw no caterpillars, and only one monarch butterfly. We may have spotted an egg on the underside of one of the leaves. Milkweed does, and seems to be able to grow just about anywhere. And, more milkweeds mean more host plants and food for caterpillars. But, there are more parts to this puzzle. Major winter forest habitat for the adult monarchs in Central America, and to a lesser degree in the far southern U.S., have been greatly reduced. Also, even though I, and other city and suburban dwellers, may notice lots of milkweed – in the farmland areas, there are less and less “weedy” patches and the milkweed populations has been dwindling there. Work is being done to restore and maintain winter habitat, and we have and can raise awareness about summer nectar and host plants here. There is quite a large colony of common milkweed in the Native Plant Garden across the driveway from Curtis Prairie, and we wondered if that was seeding the edges of the prairie. I’d like to see a time-lapse photo study of this plant through spring, summer, and fall.

“All I am saying is that there is also drama in every bush, if you can see it…” This is quote from Aldo Leopold used to open up a research paper on the common milkweed. I refer to milkweed as metamorphic. It’s just hard not to notice to the interesting changes and structure of this plant. Soon, the large soft globes full of buds will open up into 300-500 intricate flowers per plant. As summer wanes less than half of these flowers will somehow transform themselves into a spiky seed pod that will swell into fall and then burst open sending seeds across the land – attached like tiny soldiers with parachutes of whispy white filaments. Like many plants, milkweed has an arsenal of methods to establish and colonize any open ground.

At this point, we have yet to enter Curtis Prairie. On our left as we walked from the parking lot down the main path into the prairie, we saw a sea of small white pea-like flowers five or six feet in the air on the stalks of white wild indigo (Baptisia alba). On our right there has consistently been a thicket of gray dogwood (Cornus racemosa). It is a bushy shrub with rounded pyramid shaped clusters of tiny white flowers. This thicket is a prime habitat for the common yellowthroat (Geothlypis trichas), which I frequently hear in this spot. However, we didn’t hear a yellowthroat there today – but we did hear one off in the distance as we headed west by Curtis Pond. Birds plan their day a bit more thoughtfully than most humans. They get out and about early when it is cooler to save their energy.

Still in the heat of the day, we managed to hear a note or two of evidence that the most common residents – song sparrows, catbirds, barn swallows, and goldfinches were all at home in Curtis Prairie. In contrast to struggling to hear these birds, we were loudly noticed by both male and female red-winged blackbirds. They are especially attracted to the wet areas of the prairie where there are plenty of cattails, thick grasses, and shrubby willows for cover and nesting habitat. It’s also very common to see, and often hear, red-tailed hawks circling high overhead. Today, a pair of hawks was circling over the western edge of the prairie past Curtis Pond.

As you may imagine the pond and the spillway from the beltline has had an active, persistent flow this year. We noticed a heavy seeding of yellow sweet clover. It is an invasive plant that was brought here as a cover crop, to add nitrogen to the soil, and to feed honey bees – which it still can do. However, in the prairie it usually just crowds out other plants. Another tenacious plant (in this context we will call a weed) is leafy spurge (Euphorbia esula). It has lance shaped leaves, almost like thick leaves of grass that whorl out from the stem, topped by small cupped petal-like structures called bracts. In the middle of the bracts are greenish, yellow brown flowers that are very tiny, and may not be noticed as flowers without magnification. Leafy spurge is only a couple feet tall. But, don’t let its size fool you. If you are lucky enough to get them out in the open, you can spray them with herbicide. And, most of it will drip off the leaves. You can add a little soap and/or put the herbicide on with a sponge or glove to aid in adherence. If enough herbicide stays on to set it back, a few inches away another stalk will be growing – probably attached to many more stalks. It’s so difficult to get rid of this plant; ecologists are experimenting with introducing beetles that specifically feed on leafy spurge to try to control the spread of these plants. In this area, along the path by the spillway east of Curtis Pond, we have typically seen a relative of leafy spurge, which is a desirable native, flowering spurge (Euphorbia corollata). I don’t know if leafy spurge is out competing it, or whether the plants migrated out of our site, having a bad year, or something else.

Weedy and invasive plants have become a significant part of our natural areas; even well tended and managed natural areas. This will continue to challenge us to look at how usage, drainage, site location, and management practices contribute to the function and character of our natural areas. In addition to invasive plants, climate has its effects. Although, a warmer climate has brought more southerly plants to this area, this year’s cloudy and cooler spring has resulted in some later bloom times. This was most evident with the gray dogwood, which typically blooms from May through June – looking like it was just hitting its blooming stride. Likewise with black-eyed susans (Rudbeckia hirta), which typically start blooming in mid-June were also just beginning to flower.

Here’s a list of plants we saw in bloom on the eastern side of Curtis Prairie:
Wild parsnip (Pastinaca sativa) Flowers: late June – early September (watch out for this one – it can cause a severe rash if touched – we only saw a single plant right off the main path entering Curtis Prairie)

Pale purple coneflower (Echinacea pallida)
Flowers: late June – August
Tall Beard-tongue or False foxglove (Penstemon digitalis)
Flowers: mid June –mid July
White wild indigo (Baptisia alba)
Flowers late May – early August
Common yarrow (Achillea millefolium)
Flowers: June – mid October
Gray dogwood (Cornus racemosa)
Flowers: May-June
Spiderwort (Tradescantia ohiensis)
Flowers: late may- early August
Tall meadow rue (Thalictrum dasycarpum)
Flowers: early June – mid July
Carolina rose or Pasture rose (Rosa carolina)
Flowers: late May – late September
Hairy Vetch (Vicia villosa)
Flowers: late May – mid October

Paul Borowsky
Arboretum Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.