Tom's Blog

Friday, October 17, 2014

Oaks: Great fall color!

Earlier in the fall I thought the fall color was going to be a bust, but there has been a marvelous transformation over the last week. The color this year is now fantastic. Not only the maples, which are usually the most prized, but the oaks, which are the dominant species in our area. Yesterday I took at least a 100 photos (bless the unlimited capacity of a digital camera!).

The Hill's oaks are generally the most colorful oaks in our area (they are related to the scarlet oak of Illinois), and this year turns out to be no exception. The two bright red trees in this photo are Hill's, although some other Hill's are reddish orange, red, or even yellow orange.
Mixed oak area at the north side of Toby's Prairie. The red trees are Hill's oaks.

The stand of oaks in the photo below is interesting, because they are all white oaks, and all about the same age. This is a stand at the east end of the Conservancy (those on the right are part of the East Basin savanna). The color range is really wide, varying from yellow, through orange, to rather red.

These trees are all white oaks (Quercus alba), mostly about the same age (around 50 years). Striking variation in color!
The physiology and biochemistry of fall color is fairly well understood.

The shorter daylength in fall triggers a physiological process that results in the decomposition of the green chlorophyll pigment of the leaves. Remaining behind are carotenoids, pigments which are responsible for the yellow, orange, or brown colors.

The red colors come from anthocyanins which the plant produces from sugars in the leaves. Leaf sugar increases when the temperature drops and anthocyanin production begins. The amount of anthocyanin that can be produced depends, among other things, upon the sugar concentration in the leaves. This process is highly variable from year to year, depending on weather, which affects the physiological state of each tree. Another factor is genetics, which determines which enzymes are present to carry out a particular biochemical pathway.

Considering all these factors, it is understandable that leaf color can vary greatly, depending on the amount of chlorophyll remaining, the amount and character of the carotenoids, and the amount and character of the anthocyanins. There is species to species variation, as well as year to year variation. A wide variety of colors are possible, and an individual tree can vary from one year to another.

Further, some species, such as hickories, birches, and aspens, lack the enzymes for making anthocyanins, so their fall colors are exclusively yellow or orange. 

Thus, it is not surprising that the stand of white oaks shown in the photo should vary so much from tree to tree.

Friday, October 10, 2014

The Mystery of Masting in Oaks

This is the time of year when acorns are dropping and you can hear them crunch under your feet as you walk through the woods. However, only a few oak trees are dropping acorns. This year at Pleasant Valley Conservancy only one oak species seems to be producing acorns: northern red oak.

Acorns from an oak in Unit 11B at the edge of the gravel road. Listen for the crunch as you walk by!

Mast is a term used to describe the hard fruit of various trees such as beech or oak. Oaks as a group produce lots of acorns only every three or four years, and a high production year is called a good mast year. I discussed the masting phenomenon in 2011 when bur and white oak were heavy acorn producers. 

This year, so far, the only trees I have found dropping acorns are red oaks (Quercus rubra). Other oak species in the red-oak group such as Hill's and black oaks do not (so far) seem to be dropping acorns. The last good mast year for the whole red-oak group was in 2010.

It is not unusual for masting to occur only in a single species, such as we seem to be having this year, although the mechanism by which the trees bring this process about is a mystery. There are lots of papers discussing this mystery, but no concrete data. Look for the work of Walter D. Koenig, although his research has focussed on California oaks.

I was surprised to find that other oaks of the red-oak group were not producing acorns. At the east end of Toby's Prairie there is a large grove of Hill's oak (also in the red-oak group), none of which were dropping acorns. And right at the edge of that grove was a single red oak dropping acorns. (The ground was covered, just under this tree.)

How do they synchronize acorn production? Not by chemical signalling, apparently.

Wednesday, October 8, 2014

Savanna understory: factors influencing

This is a nice time for an overview of the understory vegetation in our bur oak savannas. The canopy cover varies quite a bit from one area to another, and this greatly affects the understory vegetation.

The best way to see the savannas right now is to take a stroll through the mowed trail that goes from the west end of Toby's Prairie to the Saddle Road at the west end of Unit 11A. The first part of the walk is through a savanna that is mostly closed (Unit 11B). About half way along you come out into a quite open savanna (Unit 11A). The transition is very easy to discern, because of the distinct difference in the understory vegetation. Unit 11A; open savanna: tallgrass. Unit 11B; closed savanna: sedges, milkweeds, purple Joe Pye, boneset, other forbs.

The two photos (11B; above) here show the difference.

The air photo/map below shows the approximate locations of the camera and the photo directions. The air photo, taken leaf-on by NAIP in the summer of 2013, clearly shows the locations of the oaks. The map was done by ArcGIS. The location of the gravel service road is shown by the orange dashed line.

Several items of management are relevant. The savannas were cleared of undesirable vegetation in 2000-2003 and were planted several times with open or closed savanna seed mixes. (The open savanna mix contained little bluestem, big bluestem, and Indian grass. The closed savanna mix did not have the prairie grasses.) The savannas have been burned annually since 2003 (11 years). It took about three growing seasons for the prairie grasses to get started in Unit 11A. Indian grass is the predominant prairie grass. Note that what we are seeing here is the late summer/early fall vegetation. The prairie grasses only become significant in late summer. During most of the summer a wide variety of forbs are present, including compass plant, pale purple coneflower, Canada milkvetch, etc.

Since the soil, topography, and weather are similar in both units, the most significant factor controlling the understory vegetation is light. Where the canopy is very open, prairie grasses dominate. In the more closed canopy, prairie grasses are only scattered.

Another matter of interest. Unit 11A had remnants of a prairie vegetation when we started restoration. Lead plant and New Jersey tea were present and have increased once the invasive woody plants were removed.

Friday, October 3, 2014

Filling spray bottles with herbicide

We use 16 or 32 ounce spray bottles for a lot of our herbicide applications. They are ideal for basal bark applications of small brush. They also work well for small-volume leaf applications (what I call the "herbicide spritz"). Although there is a lot of "stoop" labor in using them, the herbicide can be applied precisely and without any loss to the soil. Backpack sprayers such as the Solo are fine for large-sized shrubs or trees, but they waste too much herbicide when used for the small shrubs we mostly deal with.

The photo here shows the technique I use for filling such bottles. I do it on the tailgate of the Kawasaki Mule, which avoids the necessity to stoop. The whole procedure is done over a children's sled, so that accidental spillage is controlled. The blue bottle contains the herbicide reservoir, generally enough for a whole day's work. This bottle originally contained laundry detergent and pouring from the lip is easy to control. The box of industrial-strength tissue is a required item. When the spray apparatus is removed from the sprayer its lower tube always contains a few drops of herbicide so it is laid on a sheet of tissue. The small funnel is also laid on this tissue after it is used. When the operation is completed, any drops on the funnel, sled, or elsewhere are wiped up, the tissue folded and discarded into a trash container. The herbicide mixture being used here is 20% Garlon 4 in Bark Oil NT with an oil-soluble red dye added.

The choice of spray bottle is critical. Some work well and others are disasters. From lengthy experience, we have found that the cheap spray bottles sold at Ace or True-Value Hardware are fine, and are cheap enough so that they can be tossed as soon as they start leaking. (All spray bottles will inevitably leak.)

My rule is that as soon as a spray bottle shows the slightest sign of leakage it is tossed. At our hourly rate, the time it takes to fix and/or clean a bottle is not worth it. In addition to the time it takes to fix a spray bottle, you have the time wasted in the field with a leaking sprayer.

I prefer the 32 ounce spray bottle, which holds enough herbicide for a couple of hours work.

The ideal method for basal bark application to sumac, buckthorn, gray dogwood, black walnut, etc. is to grab a stem and pull it toward you, so that the far side of the stem base is exposed. Lean over and give a single "spritz" to the base of the stem. This is all that is needed. For small stems, only one side needs to be treated. Some of my earlier posts have details.

Monday, September 29, 2014

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.


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.

Wednesday, September 24, 2014

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!

Thursday, September 18, 2014

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.
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.

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.

Buckthorn shoots sprayed in study area
Year total
not recorded

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
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
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