ARBORETUM NEWS (NATURALISTSNOTES)

Curtis Prairie, with a Royal Diversion

SUNDAY, JULY 3, 2011

I’m going to start these notes with some information about Monarch butterflies and their eggs. We looked, unsuccessfully, for the latter during Sunday’s tour – and some questions arose that I could not answer off the cuff, but I’ve done some research now, and voilà!

At this time of year I am constantly hunting for Monarch eggs. They are always laid on milkweed plants – any species of Asclepias will do – and usually on the underside of a leaf. (Only once in my career as a wide-eyed wanderer through Nature have I found a Monarch egg on the upper surface … I guess that particular mother-to-be didn’t get the memo.)

This year I, and other observers, are reporting very few adult Monarchs, so it is hardly surprising that we aren’t finding the normal number of eggs. But we keep looking and hoping!

One of Sunday’s visitors asked how many eggs a single butterfly lays, and if she deposits just one per plant, one per leaf, or perhaps many. In my offhand observations I have only seen one per leaf – but that’s not science, that’s anecdotal evidence, so after the tour I turned to better experts for answers.

It turns out that a single female Monarch will lay hundreds, perhaps a thousand or more, eggs in her brief lifetime. Estimates vary, and it’s important to remember that the number and pattern of eggs laid by a butterfly in “captivity” (i.e., a lab setting) may not match performance in the wild. Whenever we deprive an organism of “free range”, we may distort behavior. But an Arboretum staffer who formerly raised Monarchs for research said that 700 was a reasonable average.

Generally the eggs are deposited one per plant or stalk, but exceptions happen. In fact I found a video on the Internet showing a female Monarch laying two eggs on the same leaf of a swamp milkweed plant (Asclepias incarnata). I don’t know if that footage was captured outdoors, or in a lab.

Monarch butterflies are charismatic and popular, and there are many excellent sources of information “out there” about them. MonarchWatch (www.monarchwatch.org), JourneyNorth (www.learner.org/jnorth/monarch/), and Wisconsin Nature Mapping (www.wisnatmap.org) all feature “citizen science” tracking of the butterflies’ seasonal migration.

I must digress here to a favorite book: Chasing Monarchs by Robert Michael Pyle. Some years ago, the west-coast naturalist and author Pyle followed the migration of the regal orange butterflies from Canada to Mexico – studying, philosophizing, and writing along the way. Lacking wings, he made the trip in his 1982 Honda Civic, “Powdermilk”. If you like Monarchs, you’ll love this read.

One last thing, for now, about Danaus plexippus: sometimes you find an egg on a particular plant one day, and the next day it is gone. Perhaps it hatched; the first thing the tiny new caterpillar does is to eat the egg case it just emerged from. Generally this leaves a small crescent- or D-shaped hole in the leaf. If you are really lucky, you may find the infinitesimal green larva still present on the plant. But sometimes the eggs just disappear. What, a visitor asked, might eat them? They’re way too small for birds to bother with. The answer is: spiders, ants, mites, wasps, and possibly other critters.

But these notes were supposed to be about Curtis Prairie, and here I have gone on for a full page about butterflies that we didn’t even see!

We began our tour in the Native Plants Garden, for a couple of reasons: one, it is a great place to see many blooming plants in a fairly small space and thus do a “prairie plants primer” in short order; and two, I wanted my guests to appreciate a particular vista.

Just east of the visitor center building there is a double row of limestone seating. After about June 15—when the surrounding garden plants have reached a certain height—a wonderful thing happens when you sit upon either level of the stone arc and look south. The paved pathways and service drive disappear from your line of vision; the plants near you and extending down the slope are as one with the Curtis Prairie.

I am certain this phenomenon is no accident. The Native Plants Garden was designed by landscape architect Darrel Morrison. Doubtless he had just this view in mind when he specified what plants should be used in that particular spot. Morrison no longer lives in Wisconsin, but he visits the Arboretum from time to time; some day I mean to thank him for this annual bit of magic.

On Sunday, while the visitors were seated, I read an essay by Robert E. Gard called “The Voice of the Prairie is Like the Creation”. Published in the Capital Times newspaper in February 1986, the work speaks of seeing the prairie as it was before humans came, the sadness of its near-total destruction, and the hope that people now understand the importance of preservation and restoration.

Holding those inspiring words in our minds, and having identified blooming beebalm, flowering spurge, false or “oxeye” sunflower, common and butterfly milkweed, white wild indigo, white prairie clover, rough cinquefoil, rattlesnake master, and perhaps other species I failed to record, we then set off to actually walk the prairie paths and appreciate it “close up”.

Not in bloom yet, but prominent in the central-northern part of the Curtis, is cupplant. Its large, triangular leaves “cup” the square stem and will actually hold water. Small birds drink from these tiny pools; occasionally insects drown in them. Look for yellow flowers before long.

Elderberry is in bloom here, as it was in the Grady Tract last week. After a quick introduction to the fire-tolerant bur oak grove along the central firelane, we took the narrow diagonal path across the heart of the Curtis Prairie, matching the plants we found there to the ones we’d learned in the garden. For some reason – overcast? Too hot? – the spiderwort was closed up for the day, so we were denied its lovely purple-blue color.

We paused to “boo and hiss” the villain of the Curtis Prairie: reed canary grass. A wide swath of this non-native, invasive, very hard to control species has taken over along a natural waterway through the prairie’s center. Research continues into ways to control it, or at least set it back a notch.

Though not as numerous as they were earlier in the season, wood ticks are still present in the Curtis Prairie. Please check for them while and after hiking; wearing long pants and tucking the cuffs into your socks are sensible precautions. Use of chemical repellents is a personal choice.

At the McCaffrey Savanna end of the trail, we discovered two woodland-understory plants in bloom: woodland tick-trefoil and American lopseed. (The latter is the one whose name I could not come up with immediately.) They both feature spiky pink inflorescences and wide leaves; the tick-trefoil is the one whose leaves have “drip tips” (tapered apices).

And then we were back to the Visitor Center to cool off! Next week’s tour will return to the Grady Tract. Kathy Miner, UW 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.