Rare and Interesting Species at Pleasant Valley Conservancy

Pleasant Valley Conservancy has quite a diverse plant flora. Most of the species were already present when restoration work began, but were often present only in small numbers, hidden beneath the shrubs, or carrying on in a vegetative (nonflowering) state. Some others were introduced during seeding newly cleared areas. All of the introduced species were ones that "belong" in an oak savanna and the seed sources were all local genotypes.

The Floristic Quality Index at Pleasant Valley Conservancy, a quantitative measure of the "quality" of a natural area, is quite high. Details are given on another page.

A few species present were relatively uncommon in our area and were a surprise because they only appeared after restoration began.

Purple Milkweed

Purple milkweed (Asclepias purpurascens), a characteristic species of oak savannas, is a state endangered species. It was undoubtedly present at Pleasant Valley Conservancy before restoration but it only appeared after clearing and burning in the savanna.

We first observed purple milkweed in the west part of the White Oak Savanna (unit 12B) in 1998. Part of that unit had been cleared in the winter of 1997-1998 and was burned in April of 1998. In June, we were planning management activities with plant ecologist Paul West when we saw this plant in flower. At that time, there were two clusters of flowering plants. The following year several more flowering clusters appeared. There was no seed set until 2001, when a single cluster produced five pods with seeds. Seeds from these pods were viable and a number of plants were raised, which have been planted in other savanna areas.

In 2001 another savanna area, unit 19, was cleared and burned. In that savanna, two clusters of flowering purple milkweed plants were seen in June 2002. There was no seed set from any of the plants in 2002 or 2003.



Associates of Pleasant Valley Conservancy have been asked to note any occurrences of purple milkweed on the property. The year 2004 had good rainfall in May and June, when the milkweeds are growing their fastest. Perhaps because of these favorable conditions, several new locations were discovered. In order to better understand the biology of this important species, a monitoring program was set up. Each milkweed stand was marked with a permanent metal marker, and its location recorded. By 2006 seven separate locations had been found, in white oak and bur oak savannas. At several of these sites, seed set and pods were collected. From these seeds, plants were raised in a greenhouse for transplanting into likely sites. Good growth was obtained in many of the sites, and within two or three years these plants were also flowering. In addition, new spontaneous sites continued to be found. As of 2009, 22 separate purple milkweed sites had been found. However, at several sites plants disappeared for several years and then returned.

Details of the purple milkweed studies through 2008 have been published in a paper in Ecological Restoration. This paper (with added photos) can be downloaded from this link.

The distribution in Wisconsin is shown on the map, taken from the University of Wisconsin-Madison Herbarium web site. The dots on this map represent the locations of collections that have been deposited in the herbarium. According to the Atlas of Wisconsin Prairie and Oak Savanna (Cochrane, Theodore and Iltis, Hugh, 2000): "Purple milkweed favors mesic prairies and edges of open woodlands and brushy roadbanks that simulate original savanna borders and prairie thickets."

According to the U.S. Department of Agriculture plant database, purple milkweed is endangered in Wisconsin, threatened in Massachusetts, and of special concern in Tennessee and Connecticut. In Rhode Island it is listed as "historical." An initiative is now underway in New England to reintroduce purple milkweed into that area.


Glade Mallow



Glade mallow (Napaea dioica), a handsome plant of wet prairies and marshes, is the only plant endemic to the north-central United States. On the state species list for Wisconsin, it is listed as of "special concern." Even in the states where it is found, it is rare or threatened. In Wisconsin it is found only in counties in western and southern Wisconsin. Glade mallow is a relative of hibiscus, and because of its tall size and large flower heads, it is often grown in gardens.


At Pleasant Valley Conservancy glade mallow was found originally only at the edge of the marsh at the corner of Pleasant Valley Road and County Highway F. Seeds collected have been distributed elsewhere in the edges of our wetland and this plant has spread extensively. It is now present in the Barn, Valley, and Crane Prairie, as well as in the wetland adjacent to these three sites.

Other Interesting Remnant Species


Eupatorium sessilifolium The common name of this interesting species is upland boneset or woodland boneset. It is a savanna species which is not especially common. I have seen it in three or four other sites in southwestern Wisconsin. It is sometimes confused with tall boneset, Eupatorium altissimum, which is much more common and lives in some of the same habitats. As its name implies, the leaves of E. sessilifolium are sessile, lacking petioles. The two opposite leaves come together at the stem, although they are not clasping.

In Wisconsin upland boneset is designated as a species of "special concern", implying that it is uncommon.

We had only a small population (in Unit 8) present when restoration began. This stand has spread as restoration occurred. We have also collected seed from which greenhouse-raised plants have been transplanted to other locations at the Conservancy. Most transplants have grown well, flowering and setting seed the first year. However, seed germination has been sporadic, and it has been difficult to obtain many plants for transplant.



Yellow Giant Hyssop Yellow giant hyssop (Agastache nepetoides) is another savanna plant which has a restricted distribution. In Wisconsin it is classified as "threatened." The University of Wisconsin-Madison Herbarium has collections from only a few counties in southern Wisconsin. In addition to Wisconsin, it is considered "threatened" in New York and Vermont and of "special concern" in Connecticut.

Yellow giant hyssop was apparently not present at Pleasant Valley Conservancy before restoration began. We introduced it to areas that we had begun to restore from seed collected at another site in Dane County. It has done quite well and has spread on its own. It is now found in the bur oak savanna at the top of the ridge, as well as below the ridge top on the south slope (units 2, 3, 4, 5, 6, 8, 9, 10, 11, and 19). We are using seeds collected from several of these populations to seed newly cleared savanna areas.


Prairie Turnip Prairie turnip (Pediomelum esculentum), also called pomme-de-prairie or scurf pea, is a Special Concern plant that was at one time quite common but is now rare. It was a favorite food of Native Americans, hence the common name. According to the Atlas of Wisconsin Prairie and Savanna Flora (Cochrane and Iltis), this plant is at its eastern limit in Wisconsin. It is now very rare and is restricted to relic dry prairies, mostly within the Driftless Area.

At Pleasant Valley Conservancy we have one tiny population on a remnant prairie on the south-facing slope. We only discovered it after brush removal and four or five years of annual burns.

We monitor this population closely and have been able to collect a very few seeds each year, which we are using to produce seedlings in order to extend this population. Also, seeds planted in the area of the original site have grown and plants have become established. We were also able to get a single vigorously growing plant in our forbs garden.



Sweet Indian plantain (Hasteola suaveolens) In contrast to prairie turnip, we have fairly substantial populations of this Special Concern plant. It is a handsome tall species, with copious amounts of pale yellow flowers. We find it primarily in our marshes and along Pleasant Valley Creek, although small populations also exist in our bur oak savanna. We also have a single vigorously growing plant immediately adjacent to our well house in a habitat that would generally be considered dry-mesic.

In Wisconsin, it is found mostly in the Driftless Area and in adjacent counties in the southern and western parts of the state, all of which are below Curtis's "tension zone."

It is said to be clonal, spreading by runners, and where we find one plant, we usually find a number of others. According to the native plant nurseries, this species is fairly easy to cultivate and is highly recommended for home landscaping.

In eastern United States this species is very rare, and is considered Endangered in most eastern states. A conservation program is currently underway to reestablish this species in its historic New England range.