ARBORETUM NEWS (NATURALISTSNOTES)

Public Tour – Grady Oak Savanna

SUNDAY, JUNE 30, 2013

Our tour began by walking along the path parallel to Seminole Highway, toward the V1 trail marker, where I pointed out a large decaying stump. Often overlooked, these mini-ecosystems harbor a diversity of insects and microbial organisms, working diligently to return plant-available nutrients to the soil environment. Without these communities, it would be nearly impossible for us to walk through all the woody debris that would accumulate over the years and difficult for plants to acquire enough sunlight to grow from underneath it. On the day prior, I noticed this same stump on my scouting walk and at that time, there was what appeared to be the dried out slime-mold and about 19 (I actually counted them) slugs crawling around the mold, on top of, or on their way towards it. Usually slime molds invoke a more negative response! Unfortunately, there was not much activity visible at the stump during the tour.
Shortly after turning east toward marker X2, we saw two Asclepias species on either side of the trail, making an opportune view for comparisons. On one side of the fire-lane sat the butterfly milkweed (Asclepias tuberosa),

butterflyweed

showing off its firework-orange bloom, and on the other side, the common milkweed, A. syriaca. As the name implies, milkweeds can often be identified by the milky white sap that exudes from the tissue when a leaf is torn from the stem. Butterfly milkweed, however, is one of our native milkweeds that does not exhibit this attribute. While the milkweeds were just coming into bloom, many plants of the large-flowered penstemon (Penstemon grandiflorus) had already gone to seed. We also found a patch of lupine(Lupinus perennis) seeds primed for popping. I find it interesting that lupine is derived from the Latin term for ‘wolf’ in that the plant was once thought to degrade the land it occupied. As a member of the nitrogen-fixing legume family, we now know this is far from the truth.
Although we could not access the interior trails of Greene Prairie due to high rainfall amounts over the past week, we did use the opportunity to talk a little about the differences in history and impacts of this prairie in contrast to Curtis Prairie. We reviewed how to identify the white oak (round lobes) and red oak (pointed lobes) families and located a bur oak acorn with its distinctive fringed cup.
white oak

Black oak family

It was an excellent day to spend a little time in West Grady Knoll. Cool season grasses were evident, such as needlegrass

Needlegrass

(Stipa spartea) and prairie June grass (Koeleria macrantha). The prairie clovers (Dalea sp.) were standing tall and preparing to bloom. Wildflowers that were in full bloom for us included; spiderwort (Tradescantia ohiensis-), orange flowers of puccoon (_Lithospermum sp.), thimbleweed (Anemone cylindrica), flowering spurge (Euphorbia corollata), sulphur cinquefoil (Potentilla recta), goat’s-rue (Tephrosia virginiana) and prairie larkspur (Delphinium carolinianum). I am always thrilled to see the short-statured,

Goats’rue

.yet impressive goat’s-rue in these humid summer months. Maybe the bees are thinking the same, as they appear to be just as fond of this flower as I.
Just as we exited the intersection marked Y2 and rounded the bend towards Grady Forest, someone noticed another milkweed on the edge of the trail. We looked it up in our field guides and determined it to be clasping or prairie milkweed (A. amplexicaulis)

Asclepias amplexicaulis

. Although this particular plant did not strongly express the waxy leaf margins as defined by the guide photos, the clasping leaf bases and spreading terminal inflorescence did match the description. This plant must be preferential to high quality sites with sandy soils, as it has a coefficient of conservatism rating of eight.
Overall, a successful gaze at Grady Knoll’s mid-summer offerings.

Amy Jo Dusick
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.