Two kinds of Joe Pye weed

Most people know Joe Pye weed (Eupatorium maculatum) as a wetland plant, but it turns out that it is also found in upland sites. I'm not sure why, and we certainly did not plant it, but we have scattered plants even in some of our drier and shadier oak woodland sites. The usual common name for this species is spotted Joe Pye weed. It is interesting that Cochrane and Iltis do not mention upland sites at all, indicating that it is characteristic of wet prairies, sedge meadows, marshes, and wet thickets.

Where does the name Joe Pye come from? As usual, the origin is lost in antiquity, and one is reluctant to accept any non-authoritative source. According to one book, Joe Pye was an Indian healer from New England who used plants of this genus as medicinals.



In the same upland sites where we have E. maculatum, as well as in all of our savanna sites, we have another Joe Pye weed species, Eupatorium purpureum, whose common name is green-stemmed or purple Joe Pye weed. (Kathie usually calls it woodland Joe Pye.) Cochrane and Iltis indicate that this species is common in southern dry or dry-mesic forests dominated by oaks, as well as in mesic maple and basswood forests. I have seen this species in forested habitats all over southern Wisconsin. However, according to UW Herbarium records, this species is confined almost exclusively to southern or western Wisconsin, whereas spotted Joe Pye is found almost all over the state. (The only county it is missing from is Lafayette County.)


Obviously, it is important to be able to tell these two species apart. Although some people use the color of the infloresence, the variability in color is so great that I would be reluctant to use that character. After extensive perusal of the literature, I have finally found a diagnostic character that seems to hold: the color of the stem node.

As its common name indicates, the stem of spotted Joe Pye is indeed spotted, and it has pigment up and down the stem (see the photo here).





















The stem of purple Joe Pye, on the other hand, is green (hence one of its common names), except at the nodes, at which there is a dark purple pigment (see photo at left). This pigment is very characteristic of this species. Thus, all you have to do is look at the stem nodes to tell these two species apart. I've looked at many Joe Pye weed plants and this characteristic seems to be quite consistent and very diagnostic.

Both of these species are in full flower right now, and E. purpureum is one of the commonest flowering plants in our shadier savannas.

Giant false foxglove, a hemiparasite, now starting to bloom

One of the more fascinating savanna forbs is Giant False Foxglove (Aureolaria grandiflora), a member of the Snapdragon (Scrophulariaceae) family that lives hemiparastically on oak roots. The photo here, taken by Kathie, is of the earliest flower seen this year.

There are quite a few members of the Snapdragon family that grow hemiparastically on other species, including wood betany, lousewort, and Indian paintbrush. These plants are called hemiparasites because even though they suck up nutrients from their host plants, they also have an additional extensive root system that helps support the plant. The parasitic action results when small structures called haustoria grow into the host roots where enlarged bulbous structures are formed.

Although most of the host plants of hemiparasites are grasses or forbs, A. grandiflora is especially interesting because its host is the oak tree. (The species of oak is not critical.)

At Pleasant Valley Conservancy we first spread seed of A. grandiflora about 10 years ago. The technique was to sow seed in a circle around the drip line of an oak tree. This is an area where the oak tree has an extensive root system near the surface. Some of the germinating seeds send down roots and connect with the host plant. It may take several years for development to reach the point of flowering, but once it does, A. grandiflora is able set up a perennial existence. (There is another species, A. pedicularia, that is only an annual.)

We tried to raise A. grandiflora from seed in the greenhouse. The seeds germinated well and started to form tiny plants, but without hosts they stopped growing and eventually died. This plant is interesting from an evolutionary viewpoint.

Once A. grandiflora became established, we were able to collect seeds locally and spread them further. We now have well established colonies in most of the savanna areas at Pleasant Valley Conservancy.

Bur oak longevity, but not forever

The bur oak (Quercus macrocarpa) is a long-lived tree throughout most of its range, but does not live forever. In 1997 we lost a 200-year old tree, and just last week we lost another oldie. This tree had lost a large upper branch about a year ago, and now, as the photos show, the whole tree has been uprooted. I am assuming that last year's limb loss destabilized the tree so that the large branches on the downhill side pulled the tree over, perhaps when the roots had been weakened.

I don't have the age of this tree yet but the big bur oak we lost in 1997 had 200 rings. After we get the trunk and branches cleaned up (a late fall task), we can hopefully smooth out the base so that the rings can be counted.



This latest loss was a little sad, because this was one of our most photogenic trees. In fact, Kathie's winter photo shown here won an award about 10 years ago. The tree that came down is the one on the right.

These two trees have always been a landmark at Pleasant Valley Conservancy which we have called "the two bur oaks". Now that there is only one, the landmark is gone.

Last week another large bur oak in the neighborhood went down also. This tree was in the pasture on the Schultz farm, about a mile away (see photo below). According to Jim Schultz, this tree uprooted suddenly last Wednesday evening about 9 PM at a time when there was not even a breath of air. Presumably it had also become destabilized in an early wind event, and finally gave up the ghost.

I was saddened to see the Schultz tree go because it was such a characteristic open-grown pasture tree, sitting all alone on its hillside. I have always assumed that Schultz's hillside was characteristic of what many southern Wisconsin pastured savannas looked like when they were heavily grazed. Even though all the understory was gone, the character of the savanna could be observed by the shapes of the big old bur oaks.

New edition: Fire effects: Bur oak

The fire effects series by the U.S. Forest Service is very useful for those carrying out prescribed burns. An updated edition (2011) of the site on Quercus macrocarpa (bur oak) has just appeared, written by Corey L. Gucker.

I was pleased to have contributed the introductory photo used in this site.

Here is the link:

The bur oak is the most widely distributed of the North American oaks, but its abundance has decreased dramatically since European settlement. Hence, conservation and restoration of bur oak has become a management priority throughout its historic range. Bur oak savannas in the Midwest and Great Plains were considered ideal sites for European settlers. Agricultural and urban development, and fire exclusion, were the principal factors in the loss of bur oaks.

However, because of its adaptability, restoration of bur oak can be readily carried out.

The Fire Effects review provides an excellent overview of the ecology and silviculture of bur oak.

Purple and white prairie clovers

It has taken us some years but we finally have these two conservative prairie species established at Pleasant Valley Conservancy. Although we had a small population of native Dalea purpurea before we started restoration, it wasn't large enough to serve as a useful seed source. However, there was a tiny remnant along Old Indian Trail (less than a mile away) that had a nice seed source. (Unfortunately, that population is now virtually gone, having been replaced by crown vetch. Grrr!)

We now have nice stands of both species in several of our planted prairies, as well as on the remnant prairie on the south-facing slope in Unit 6.

White prairie clover (Dalea candida) is growing in the same areas as D. purpurea, but in larger patches. This is reasonable, since Cochrane and Iltis state that D. candida is the most widespread of the approx. 160 species of Dalea in the New World.

Both species are sensitive to grazing, reasonable since they are legumes. This probably explains why we originally had D. purpurea only in those parts of our south-facing slope remnant that had been protected from grazing.

The NRCS requires D. purpurea (1-2 ounces per acre) in the seed mix used in Wisconsin when planting a prairie as part of the Conservation Reserve Program (CRP). No explanation given, but I assume it is because of the desirability of having a legume in the mix. (Canada milk vetch, another legume, is also required.)

I suspect that neither of these species will ever "take over" a prairie, whether planted or remnant. At Black Earth Rettenmund Prairie, where both species were present in the original prairie, neither one has ever become dominant, although they are always present in substantial amounts.

Getting rid of alfalfa in planted prairies

Alfalfa often remains as a residue in prairies that have been planted in former ag fields. It can also invade prairies from adjacent croplands.

For years we have been trying to eradicate scattered alfalfa clumps at Black Earth Rettenmund Prairie. Digging has been unsuccessful, which is not surprising since alfalfa is a persistent perennial. You can never dig up all of the underground root system.

We now have a technique that works. We use 20% Garlon 4 diluted in bark oil and carefully spray the bases of the stems (the "basal spritz"). This is analogous to the basal bark technique used for woody plants. Note that the herbicide is confined only to the bases of the stems, and only a small amount needs to be used.

The photos show dead plants surrounded by unaffected "good" plants.

Not only is the basal spritz technique very effective, but it is a lot quicker than digging.

I haven't checked to see if a lower concentration of Garlon 4 would work.

Note that Garlon 4 is the oil-soluble form of triclopyr.

This technique also works well for other perennial weeds that are not rhizomatous, such as bird's foot trefoil.

Lead plant

Lead plant (Amorpha canescens) is about at its peak of flowering. This legume is one of the preminent prairie plants and is usually considered desirable in any prairie planting. However, our experience has been that it is generally hard to get established from seed, although it flourishes in remnants. According to the literature, it is quite palatable to livestock and hence disappears under any significant grazing pressure.

At Black Earth Rettenmund Prairie, which has never been grazed, lead plant flourishes, although it is not present uniformly. It seems to be absent from those areas that before restoration were heavily wooded, and has not returned even though these areas have been clear of woods for over 25 years.

At Pleasant Valley Conservancy lead plant was present before restoration began at four remnant sites (Units 1, 4, 11A, and 23), but was absent at sites that had been grazed. However, although we had what we considered good seed sources, we have been unsuccessful in getting it established in any of our planted prairies.

On the other hand, we have been very successful in getting lead plant established from seed at the Gateway Prairie, the small restoration that we initiated near the Rettenmund Prairie entrance in 2005. In a casual survey yesterday, I found over 50 flowering lead plant patches scattered all over this 2.5 acre site. I'm not sure why we have been successful here but not at Pleasant Valley Conservancy, but it is gratifying to know that seeding does sometimes work.

Savanna species diversity

This is the time of the year when one can get a good idea of the species diversity of a prairie or savanna. Most of the early-blooming species are still around (forming seeds) and the late-blooming species have made substantial vegetative populations. And there are lots of species flowering at present.

We have been keeping notes on the prairie and savanna species diversity since 1998, and since 2002 I have attempted to record every species present in each management unit. The data for the years 2002 through 2008 are extensive, and have been analyzed carefully. Although the analysis is a winter project, the utility becomes evident in the summer.

I made an Excel table that lists every species present in each of the savanna management units. Today (4th of July) I found the time to convert this table into a PDF that could be downloaded by those interested in savanna species diversity.

Download the table

These data can be analyzed in a number of different ways, but what I chose to do here was to sort by C value (Coefficient of Conservatism), since this put the most interesting species at the top of the table.

There are some species missing from this table, including a few new ones discovered since 2008. But even so, there are 238 species in this table.

One value of this table is that because it locates each species by management unit, it shows which species are really common, and which are fairly rare. At least part of the variability between units is due to canopy cover. Some of the units have lots more open canopies than others, which leads to more area where "prairie-like" species can develop.

Comparisons of canopy cover in different units can be found at this link.

As I have noted elsewhere, the species diversity in a savanna is lots higher than in either a prairie or woodland.