Fall color: good time to find sumac invaders

Those following these posts know that sumac has been one of our serious threats and that we have worked out methods for its eradication. One of the secrets is early detection followed by immediate control. Because of its intense red color in the fall, this is an ideal time for making sumac surveys.

Large clones are of course easy to find. However, a prairie restorationist may be unaware, during the summer when the sumac leaves are green, of how serious a clone has become. (See the photo below, which is not from either of our sites.)

High quality prairie remnant being invaded by three sumac clones.
Left unchecked, these clones might eventually take over the whole site.

For the two sites that we manage, we have worked hard to eradicate sumac. Our goal is to have no sumac on the site, not even single plants. We wait patiently for sumac's intense red color to develop and then do a thorough canvas. We pick a good day when the sky is clear and the sun is shining. Yesterday was perfect and Kathie and I spent most of the day looking for sumac plants. A good pair of binoculars is very useful, as single patches of red on a hillside can be due to various species, most of which are lots less harmful than sumac.

These include woodbine (Parthenocissus quinquefolia; intense red), hazel (Corylis americana; deep maroon), and gray dogwood (Cornus racemosa; dark red). Only sumac has compound leaves, which are usually easy to discern at a distance. The photo below shows how easy it is to spot a single sumac plant.

Results?

At Pleasant Valley Conservancy we found 10 single plants scattered over about 50 acres of oak savanna. None of these were on prairies, either planted or remnant. Only two patches were clones, but each of these was small (ca. 5 feet in diameter). When found, clones or single plants can be immediately treated by basal bark with Garlon 4 in oil. It is important to even treat single plants, because each plant has the potential for forming a clone. It was indeed satisfying that we saw so very little red!

At Black Earth Rettenmund Prairie we found only one clone of any size, and this was on the neighbor's pasture. There were 8 plants scattered over this 16 acre remnant prairie.

So little sumac? How could we be so lucky? Hard work and persistence.

Although we started to work on sumac in 2008, it was not until 2011 that we got serious. Using GPS (and GIS) we had mapped all the sumac clones on each site. The details of how we eliminated sumac are given in several posts, which are summarized in this link.

I should emphasize that we can't relax just because we have essentially eradicated sumac from these sites. Sumac is a prolific seed producer, and birds move these seeds around very effectively. If we drop our guard, we may soon find new clones. Also, single plants that we have missed have the potential for starting new clones. 

Restoration work is never finished.

Classic open-grown savanna oak

I couldn't resist posting this fine image of the signature bur oak at Pleasant Valley Conservancy. The weather has been very fine in late September this year, and with clear skies the vegetation really shines.

Although the bur oaks never show much color, the other oak species are starting to turn. The Hill's oaks usually have especially nice color, especially in the borders around Toby's Prairie.

Come out and see them!

Buckthorn eradication: results of a five year study

Because of buckthorn's importance, there have been many earlier posts from Tom's Blog. A list of these posts, with URLs, can be found at this link.
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Buckthorn is probably the most difficult shrub to get rid of in prairie and savanna restoration (it’s at the top of IPAW’s list). Because of its strong allelopathic nature, if unchecked it can form extensive monocultures.

Removal of buckthorn requires the use of an herbicide, either as a basal bark or cut stem application. Although these treatments are very effective, they do not eradicate an infestation for two reasons:

•  There is almost always an extensive seed bank. This is fairly easy to control, and only persists for several years.
• There are numerous dormant root masses capable of sending up new shoots, and these are a much more difficult problem. Experience has shown that these viable structures can remain alive for at least 15 years, perhaps longer, even if any new shoots they form are mowed or top-killed by annual fire.

What I am reporting here are the results of a long-term study I carried out at Pleasant Valley Conservancy. The area used was a small part of a much larger bur oak savanna which was first cleared of buckthorn in the 1999-2000 period. The initial fairly large-diameter shrubs were killed by basal bark treatment with Garlon 4 in oil. After the shrubs had died (which took about two years) they were removed when the savanna was restored. Since then, the site has been burned annually.

Despite annual burns, new buckthorn shoots kept appearing every year. Each shoot was part of an extensive underground root mass. Five years ago I decided to see how long it would take to get rid of them. I think I have finally succeeded.

The preliminary work for this study was described in a 2011post, which should be read for details on this study. 

Starting in 2010 I canvassed the site carefully and sprayed with Garlon each buckthorn shoot, counting as I proceeded. In the three early years, when there were lots of shoots, I returned over and over again at 2-3 week intervals. At the end of the season, I made sure that there were no live buckthorn shoots left.

The table shows the results. I should emphasize that the effectiveness of my spraying is not in question. Thus, a shoot found in 2012 is not one that had been sprayed in 2011 and not killed. My conclusion is that in this small area there were many dormant root masses, but not all of them left dormancy the same year.

Year	Buckthorn shoots sprayed in study area	Year total
2010	not recorded	>300
2011	12+30+71+35+27	175
2012	17+18+55+5+44+20+82	241
2013	6+7+8	21
2014	0	0

Another conclusion is that it is possible to eradicate a site of buckthorn, but the site must be revisited in multiple years.

One might ask what effect this multiple spraying might have on the natural flora. That’s a lot of Garlon! I should emphasize that I was careful with my spraying, making sure that nearby “good” plants were not treated.  The table below is the species check list I made this year, when no spraying had been done. The diversity is satisfyingly high! Note the presence of Gentiana alba, a State Threatened species. There are actually two separate patches of this species, one of which has numerous stems, and both patches flowered.

Latin name	Common name
Actaea rubra	Red baneberry
Agrimonia gryposepala	Tall agrimony
Allium cernuum	Nodding wild onion
Amorpha canescens	Lead-plant
Andropogon gerardii	Big bluestem
Anemone virginiana	Woodland thimbleweed
Asclepias syriaca	Common milkweed
Asclepias verticillata	Whorled milkweed
Aster ericoides	Heath aster
Aster novae-angliae	New England aster
Aster sagittifolius	Arrow-leaved aster
Campanula americana	Tall bellflower
Desmodium glutinosum	Pointed tick-trefoil
Desmodium illinoense	Illinois tick-trefoil
Elymus hystrix	Bottlebrush grass
Eupatorium altissimum	Tall boneset
Eupatorium purpureum	Purple joe-pye weed
Gentiana alba	Cream gentian
Gentianella quinquefolia	Stiff gentian
Heliopsis helianthoides	Ox-eye sunflower
Hieracium kalmii	Canada hawkweed
Lactuca canadensis	Tall lettuce
Monarda fistulosa	Wild bergamot
Ratibida pinnata	Yellow coneflower
Rudbeckia hirta	Black-eyed Susan
Schizachyrium scoparium	Little bluestem
Silphium integrifolium	Rosinweed
Silphium terebinthinaceum	Prairie dock
Solidago rigida	Stiff goldenrod
Solidago speciosa	Showy goldenrod
Sorghastrum nutans	Indian grass
Sporobolus heterolepis	Prairie dropseed
Toxicodendron radicans	Poison ivy
Tradescantia ohiensis	Common spiderwort
Verbena stricta	Hoary vervain
Zizia aurea	Golden Alexander

Baltimore oriole nest

We've been having Baltimore orioles nesting near our cabin for quite a few years. They build their characteristic nest in a nearby decrepit elm. We ought to fell this tree but won't as long as the orioles  use it.

Several days ago during a stiff wind the oriole nest, now no longer used, came down and Kathie found it. The structure is impressively complex, as the photo shows.

How do they make it?

According to the Cornell bird web site, the female weaves the nest from various types of fibers: grass, strips of grapevine bark, and wool, as well as artificial fibers such as twine or fishing line. They may also use fibers from an old nest to build a new one. Males may occasionally bring nesting material but don't help with the weaving.

The nest is built in three stages:

1. Construction of an outer bowl of flexible fibers for support
2. Springy fibers are woven into an inner bowl, which maintains the bag shape
3. Addition of downy fibers and feathers to provide a soft lining which cushions the eggs and young.

They do one brood a year and the clutch size is 3-7 eggs.

At lunch we spent some time looking at the structure. Under a hand lens the fibers of this nest looked mostly like bits of cloth, although it was also possible to see strands of plant material. According to Cornell, no knots are tied, but some do arise due to random poking of fibers.

It's hard to imagine how someone without hands can make such a structure!

Story of a small prairie parcel

When we started restoration about 15 years ago, the parcel under discussion here consisted of a small clone of quaking aspen, about 0.2 acres. The trees were girdled in 1998 and the dead logs were removed 2 years later. Two medium-sized Hill's oaks were left standing and are thriving.

 Because this small area was an orphan trapped between our gravel service road and a small CRP parcel (the Ridge Prairie), we more or less ignored it. Although we don't have any specific records, we may have planted it once or twice with a dry-mesic seed mix. However, beginning about 2007 or 2008 it had become mostly a solid patch of Canada goldenrod (Solidago canadensis). In mid-summer 2008 the whole patch was mowed with a brush cutter to try to get a handle on the goldenrod. After that, all we have done is burn it when we burn the adjacent Ridge Prairie. It has been burned annually since then (7 or 8 burns) and otherwise it has been ignored.

I never paid any attention to it since I assumed that it was still predominantly Canada goldenrod. Last week I looked more carefully and realized that most of the Canada goldenrod had been replaced with a surprising diversity of forbs and graminoids, including some relatively uncommon species.

The photo shows one part of this parcel, with the Ridge Prairie in the background. (The nearest tree is probably a Hill's oak.)

The table below shows the results of my quick survey.

Latin name	Common name
Aster ericoides	Heath aster
Aster lateriflorus	Calico aster
Aster novae-angliae	New England aster
Aster pilosus	Hairy aster
Aster sagittifolius	Arrow-leaved aster
Baptisia alba	White wild indigo
Carex pensylvanica	Pennsylvania sedge
Cirsium discolor	Pasture thistle
Corylus americana	American hazelnut
Desmodium canadense	Showy tick-trefoil
Desmodium illinoense	Illinois tick-trefoil
Elymus riparius	Woodland wild rye
Eupatorium perfoliatum	Common boneset
Gentianella quinquefolia	Stiff gentian
Monarda fistulosa	Wild bergamot
Prenanthes alba	Lion's foot
Ratibida pinnata	Yellow coneflower
Rudbeckia hirta	Black-eyed Susan
Silphium integrifolium	Rosinweed
Silphium perfoliatum	Cup plant
Smilacina racemosa	False Solomon's seal
Solidago canadensis	Common goldenrod
Solidago nemoralis	Gray goldenrod
Solidago rigida	Stiff goldenrod
Solidago speciosa	Showy goldenrod
Sorghastrum nutans	Indian grass

Some of these species probably moved in on their own, since it is unlikely we would have had them in a seed mix. Noteworthy are Lion's foot and stiff gentian, which are hardly "weedy" species.

I'm convinced that the frequent (annual) burns played an important role in transforming this parcel from a monoculture to a diverse prairie.

It is encouraging to see what burns and patience can bring!

Mysterious Silphium dieback summer 2014

Have other prairie restorationists observed this?

At Black Earth Rettenmund Prairie a major dieback of Silphium species is occurring. Strikingly, at Rettenmund this has only occurred in the areas that were not burned in the spring of 2014.

This die-back was most dramatically revealed with compass plant (Silphium laciniatum), one of the signature species of the prairie, but rosin weed (Silphium integrifolium) is exhibiting the same phenomenon. In other sites (also unburned) in southern Wisconsin, the two other Silphium species, cup plant and prairie dock (not present at Rettenmund), are also suffering from this die-back. 

 As often happens in restoration ecology, this dieback creeped  up on me. The leaves of compass plants grew normally in late spring/early summer. Most plants had a lush complement of typical leaves. But in mid-June, no flower stalks developed at the time they normally would appear. Since the compass plants in the areas that had been burned were flowering normally, I knew something was wrong. But what?

By mid August all the compass plant leaves had turned brown. A survey of compass plants at Rettenmund indicated 100% dieback. 

Because of its structure, the situation with rosin weed was somewhat different. All the rosin plants grew normally but at the time they would be flowering they began to turn brown. The flowers on any plants that had already started developing aborted. Again, 100% effect.

Since we did not have the other Silphiums at Rettenmund, I visited a few other sites in Dane County. Both cup plant and prairie dock also showed the same phenomenon. 

The end result? Unless the site was burned, there may be no Silphium seeds to collect!

I am trying to document the extent of this dieback and would welcome reports from others who have experienced it.

One more thing. All of the other species at Rettenmund are growing and flowering normally except flowering spurge (Euphorbia corollata), which has also shown 100% dieback.

Let me emphasize that sites that had been burned this spring are not exhibiting this dieback.