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. Also, we found several clusters that could be clearly identified from the leaves but did not flower. 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. Seven separate locations are now known, three in white oak savannas and four in bur oak savannas. At three of these sites, seed set occurred in 2004, the first time since 2001. However, at one site, plants did not return after the first summer. In another site, plants disappeared for several years and then returned. We will continue to monitor all purple milkweed sites at Pleasant Valley Conservancy.

Although the plants in the field are highly variable, tests on the seeds collected have shown that their viability is high. It is relatively easy to raise plants from seeds. In 2005 we set up a forbs garden near the field station, and purple milkweeds have been grown there since that time. We raised seedlings and transplanted them into this garden. The first year they grew but did not flower. The second year they flowered well but did not set seed. The third year they flowered very well and set seed profusely. Specimens from the third-year plants were collected and deposited at the University of Wisconsin-Madison Herbarium.

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 have been distributed elsewhere in the edges of our wetland and this plant is now spreading. In 2004 we had good seed set in the planted corn field near the barn which we call the "Barn Prairie." It is also becoming established in our other wet prairies.

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 have only a small population, which was present when restoration began. We are working to establish this species at other locations in the Conservancy. This is proving difficult because seeds collected in nature have poor viability. We have been able to raise in the greenhouse a few plants from seed, and transplanted them to suitable locations. The transplants seem to grow well and flowered the first summer.

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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 that might be used to extend this population.

 

 

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. This species is considered an obligate wetland species by the Nature Conservancy, but other sources call it facultative wetland, meaning it grows in both wetland and nonwetland habitats.

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.