ARBORETUM NEWS (NATURALISTSNOTES)

Grady Tract/Greene Prairie Tour – Naturalists’ Notes

SUNDAY, AUGUST 17, 2014

The small parking lot at Seminole Highway and the West Beltline frontage road was filled to overflowing by 10 minutes to one o’clock on Sunday. Two dozen people had an appetite for the summertime prairie!

And I don’t think anyone went home disappointed. We saw many of the same plants that have been mentioned over and over in these naturalist’s notes – white snakeroot, pokeweed, Virginia creeper, poison ivy, and the like. But we also had a few surprises.

One of those was large-flowered yellow false foxglove,Aureolaria grandiflora. We spotted a single specimen in conspicuous bloom on our way up the West Knoll; I confess that it was a visitor who identified it for me, saving me some time thumbing through my Prairie Plants book.

It’s hard to overlook these big, bright-yellow flowers. They have the deep funnel shape typical of the foxgloves. The leaves, which lie opposite one another along the stem, are almost fernlike. The fine print in my field guide informed us that the plant is a root parasite, on oak trees in particular, and voila! There it was, growing very near a red oak.

The book also says that yellow false foxglove’s leaves turn blackish when bruised or picked. I did not test this feature during our tour, but I may go back at a later time to check it out.

Another delightful discovery was the field milkwort (also known as blood milkwort), Polygala sanguinea. Some years I miss this humble plant entirely, but on Sunday’s tour, we just kept seeing more and more of it. Looking a bit like a miniature thistle, it’s in bloom along the interior trails in the Greene Prairie. But it’s only ankle-height, so look down!

This milkwort’s flower is pinkish-lavender, with tightly overlapped petals forming a roundish, dense head. Leaves are slender and almost grasslike. And here is a bit of botano-linguistic trivia: the “milk” part of the name does not signify that the plant has milky sap, like the milkWEEDS do. Rather, the milkWORTS – at least the European species – were thought to be a lactation aid for nursing mothers. I have not (yet) found anything to explain the “blood”/sanguinea part.

Yet another annual late-summer treat in the Greene Prairie is lady’s tresses, Spiranthes magnicamporum. We found just a few specimens in flower on Sunday, but this was expected, since it really comes into its own around September 1st. I always think of lady’s-tresses as marking the cusp between summer and fall.

The ones we saw were not the showiest flowerheads I’ve ever seen – actually kind of scraggly. (Perhaps the lady needs a change of hairdressers, or a better styling product?) The inflorescence is a spike, with a twist (literally): the stem actually spirals, making the flowers appear to have been braided into it. Fascinating factoid of the day: the flowers are protandrous, changing from male to female as they mature.

UW graduate student Matthew Pace has been studying Spiranthes in the Arboretum, in particular their pollination, which is mostly accomplished by bumblebees. He reported last February that despite hours of observation in 2012, he saw NO pollinator visits. (Now I am wondering if that has anything to do with how few lady’s tresses we’re seeing right now. Or is it simply too early in the season? Hmm, an E-mail to Matt might be in order.)

Matt found the flowers to be less fragrant than expected. That could lead to less pollinator interest. Other possible causes might include: competition from taller, showier plants nearby; the general decline of native pollinators across North America; and/or factors relating to the 2012 drought. He plans to continue monitoring lady’s tresses, possibly utilizing cameras. Stay tuned!

A few turtlehead (Chelone glabra) plants can be seen in bloom as one first enters Greene Prairie from trail marker Z1. You have to view the flower from just the right angle to see the resemblance between it and a turtle’s head. Like some gentians, turtlehead’s flower lips remain closed, forcing pollinators (bumblebees again, in fact only long-tongued ones) to squeeze between them in order to obtain nectar, and oh by the way, accomplish pollination, which is what the plant wanted all along. The genus Chelone, meaning “tortoise”, prefers wetter locations; it’s related to snapdragons.

Here’s something we significantly DIDN’T see: prairie dock in bloom. Or its close relative compass plant, for that matter. We saw 2 or 3 very short stems of the former, with tight green buds; none of the latter AT ALL (though many leaves are evident). Some prematurely brown, curled leaves of prairie dock suggest that something is getting to the Arboretum’s Silphiums – possibly the Silphium borer moth, Papapaima silphii? If true, this would be good news for the moth – which has endangered-species status in Wisconsin – but bad news for those of us who love the yellow flowers of the late-summer prairie. To every thing there is a season, I suppose.

I would be remiss not to mention the Artemisia species currently showing off on the West Knoll: wormwood (A. campestris) and white sage (A. ludoviciana). Wormwood is especially noticeable, with its tall reddened stems, superfine featherlike leaves, and upright clusters of round greenish flowers which would probably escape our attention except that there are so many of them. White sage forms large silvery patches amongst the other plants’ greenery.

Hitch-hiking seeds are definitely showing up in prairie and at woodland edges – watch for the tick trefoils, enchanter’s nightshade, beggar-ticks, stickseed, and the like. Check your sleeves and pant legs after each hike. You are being recruited as a seed-disperser!

Kathy Miner, 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.