Oak Savannas

 
 

The term "oak savanna" refers to a plant community with scattered "open-grown oaks". surrounded by grasses and forbs. Other terms sometimes used are "oak opening" and "oak barren." In contrast to an oak forest, which has a closed canopy (approaching 100%), the savanna canopy ranges from 10% to 60%. Although oak savannas are found in other parts of the United States, in southern Wisconsin and throughout the upper Midwest they were once a dominant vegetation type. Originally, about 30% of the vegetation in southern Wisconsin was oak savanna.

It has been estimated that only about 0.01% of the original oak savanna of Wisconsin still remains. The remaining fragments of oak savanna thus constitute a rare and highly endangered community.

Fortunately, Pleasant Valley Conservancy has around 30-50 acres of oak savannas, and restoration work has created one of the best examples of the oak savanna type in southern Wisconsin.

For extensive information on oak savannas, including restoration methods, follow this link to a web site which is maintained by the Savanna Oak Foundation, Inc.

How do we recognize an oak savanna? The key characteristic of the oak savanna is the open-grown oak, a tree that has developed in the open, away from other trees. Savanna oaks usually have large lower branches, an indication that they developed without competition from nearby trees. The photo below, of a bur oak, is an example.

"He who owns a veteran bur oak owns more than a tree. He owns a historical library, and a reserved seat in the theater of evolution." Aldo Leopold

The presence in the habitat of open-grown oaks is a good indication of a savanna. Even if the habitat was later heavily invaded by other trees and exotic brush, the open-grown oaks may still be present.

Large areas of highly degraded but potentially good oak savannas still exist in the Midwest, especially on the south-facing slopes and ridge tops. Examination of old air photos, such as the 1937 ones taken by the U.S. Soil Conservation Service, show many highly degraded areas that still have open-grown trees. The existence of these open-grown oaks at Pleasant Valley Conservancy was a principal reason why restoration work was undertaken.

One of the principal reasons for clearing the undergrowth from around these open-grown oaks is to encourage acorn production. Acorns are the most important wildlife food and acorn production is best in healthy oaks that are able to "spread their wings".

Aesthetics of the Oak Savanna Landscape

Surveys of attitudes and perceptions have shown that the oak savanna landscape rates highly in the public mind. Open forests with large, relatively old trees are considered very attractive. Other pleasing factors of the oak savanna include the high plant diversity, the presence of wild flowers, the large openings surrounded by trees, and the extensive vistas and overlooks. These are characteristic of parks, and the park-like setting of oak savannas is appealing, just as it was to early travelers through the Midwest.

Attractiveness of the Oak Savanna
Large trees
Open forest understoreys allowing views deep into the forest
Herbaceous vegetation on the forest floor all summer
Appearance of easy travel through the forest
Large openings surrounded by trees
Relatively old trees
Best acorn production (important as food for wildlife)
Outstanding habitat for wildlife
Provides critical habitat for many bird species (cavity nesters)
Bur oaks support large diversity (over 600 species) of butterflies and other desirable insects
Highest plant species diversity; greater than either prairie or woodland
Vistas, overlooks, water bodies, unique geological formations
Flowering trees or other flowering vegetation
Some of this information from Johnson, Paul S. et al. 2009. The Ecology and Silviculture of Oaks, 2nd edition. CABI International, Cambridge, MA and Bringing Nature Home by Douglas Tallamy, University of Delaware Press.
 
Classic open-grown bur oak in a restored savanna at Pleasant Valley Conservancy. This unit has been burned annually for the past thirteen years.

 

The Importance of Fire Probably the most common reason why the oak savanna community has disappeared is because of lack of fire. This is a fire-controlled vegetation. The oaks themselves are fire-resistant, whereas weedy trees such as walnut, elm, maple, and ash are not. In presettlement times, fire was used by Native Americans to keep the woods open and to control woody shrubs. As late as the 1950s, farmers were using fire for similar purposes and to bring about early "green-up" of their pastures. However, protection from fire became an established practice of the U.S. Forest Service, as well as the Wisconsin Conservation Commission (the forerunner of the Department of Natural Resources). Although fire is a real danger in the coniferous forests of northern Wisconsin, not so for southern oaks. We know now that it was wrong to prevent fires in the southern oaks. Oaks do not suffer from the disastrous crown fires that rage through the coniferous forest. Except under unusual circumstances, fire in an oak woods is confined to the ground, to the leaf litter. Oak leaves are unusually susceptible to fire. When they burn, weedy woody vegetation such as prickly ash, buckthorn, and honeysuckle is killed, thus keeping the woods open. An open woods encourages the growth of grasses and flowering plants, which are part of the glory of an oak savanna.

Ideas have changed completely about fire in the woods. Without fire, restoration of an oak savanna is difficult, expensive, and generally unsuccessful. Research in Wisconsin, Illinois, Minnesota, Missouri, and Iowa has shown clearly that fire is not the enemy of the oak forest, but its friend.

 

Fire in a bur oak savanna. This is a typical oak savanna burn on the south-facing slope. The fuel is primarily little bluestem and Indian grass. This type of fire is called a "strip headfire." Horizontal strips about 50-75 feet apart are lighted, starting from the top of the hill. By keeping the strips close together, the flame heights remain fairly low, and the oaks are unaffected. Note that when the drip-torch operator walked across the hill, fire was "dropped" at intervals. Within minutes these separate patches of fire will coalesce and form a flaming front.
Photo series on doing an oak savanna burn (PDF download)

 

The Seasons of an Oak Savanna Download a brief slide show (PDF) that shows the transition of an oak savanna through the seasons.

 

 

 

Restoration of an Oak Savanna A principal activity in oak savanna restoration is the "daylighting" of oaks, removing trees that are crowding out the oaks. The bur oak in the above photo is a good example. This oak, whose age is estimated at about 200 years, was virtually invisible when restoration work began, being completed crowded with elm, cherry, and buckthorn. Once daylighted, the lower branches could thrive again, and the tree has been saved for posterity. Note also the other open-grown oaks farther up the hill. The open-grown oak is a handsome specimen which has often survived from the period before European settlement.

A summary of the restoration work on a single small savanna unit at Pleasant Valley Conservancy was published in the Proceedings of the 2004 North American Prairie Conference and can be downloaded here as a PDF.

Oak Savanna Locations at Pleasant Valley Conservancy The savanna habitats at Pleasant Valley are in the areas where fire would have been most common. These include the south-facing slope and the part of the ridge top that is nearest to the south slope. Because the south-facing slope receives intense sunlight, it is much drier (more xeric) than the north-facing slope. Historically, the whole south slope was prairie, and fire would have spread quickly up into the savannas.

Digital photos taken with a fish-eye lens have been used to measure the openness of the canopy. The principal savanna area is on the upper south slope and the ridge top, where many large open-grown bur oaks are present. In this savanna zone, the canopy ranges from about 25 to 70% cover. The oak woods, where there are no open-grown oaks, has canopy cover around 90%.

At Pleasant Valley Conservancy, we have oak savannas of two types, bur oak and white oak. Our bur oak savannas are in two areas: on the upper part of the south-facing slope, and on the top of the ridge, on the dolomite cap. The white oak savanna is mainly on the Jordan sandstone just below the dolomite.The distribution of these large savanna oaks is shown in the photo below. Note that shown are only the very large oaks. We have 545 bur oaks and 621 white oaks in our tree database greater than 10 inches in diameter. (The total count of all species with specimens greater that 10 inches in diameter is 4070.)

Canopy cover analysis of Pleasant Valley Conservancy savannas.

A transect was run uphill from Pleasant Valley Road, across the ridge-top, and downhill to County F. Along this transect, the canopy cover was measured using digital photos that were taken with a fish-eye lens. The results are shown here. The graph shows that savanna is distributed on the upper part of the south slope, and on the ridge top. On the north slope, the canopy cover is 90% or greater, which is characteristic of an oak woods.

 

Tree database

In recent years, as one of our winter projects, we have set up a database of all the trees at Pleasant Valley Conservancy. Each tree 10 inches diameter or above has been given a permanent number marker, has been measured, its species determined, and its location recorded by GPS. This database was completed in late January 2011 and is now being used for various queries. ArcGIS has many powerful options, and examples can be found on this web site, or on Tom's Blog.

Distribution of oaks at Pleasant Valley Conservancy

The database has been used to map the distribution across the Conservancy of the five oak species. In the first map below the species are color coded so that they can be distinguished. Although there is some overlap, in most cases each species has its own niche. To make the distributions clearer, each individual species is mapped separately below.

 

Bur oak

The most numerous species on the Conservancy is bur oak (Quercus macrocarpa). As the map shows, bur oaks are found primarily in savanna areas on the south-facing slope and on the ridge-top savanna. The bedrock underneath most of the bur oak areas is dolomitic.

 

White oak

White oaks (Quercus alba) are found in four areas. The two areas to the left in the map are white oak savannas. The other two areas are closed oak woodlands. The bedrock in the white ok areas is primarily sandstone.

 

Red oak

The red oaks (Quercus rubra) are part of a closed-oak woodland which is found principally on the north-facing slope.

 

Black oak

Black oaks (Quercus velutina) are scattered across the preserve but special concentrations are present in the three area shown on the map below.

 

Hill's oak

Hill's oak (Quercus ellipsoidalis), also called northern pin oak, is a relatively minor part of the oak population and is found in the two areas shown on the map. This species is found only in the upper Midwest, primarily on dry to dry-mesic sandy sites. The population to right on the map below is very sandy, but the other population is on soils derived from dolomite which are not sandy.

 

 

Canopy cover

Using the tree data, it is also possible, using nomographs developed by the U.S. Forest Service, to calculate the percent canopy cover of any stand. The table below gives the data for all of the savanna areas, and for some of the oak woodland areas.

Needed for the calculations are the basal area (in square feet) per acre, and the number of trees per acre. These two measures are marked on the X and Y axes on the Forest Service graph, and the canopy cover in percent is read off the nomograph.

As the table shows, those sites that are open savanna have fairly low crown covers, whereas the oak woodland sites have high or complete crown cover. In between the open savannas and oak woodlands are a few sites that are best called "closed savanna".

When selecting species to plant in the understories of a site, it is important to consider the canopy cover of that site, since some plant species thrive in sunnier sites than others. Thus, understanding the canopy cover is useful in planning seed mixes for various sites.

 

Basal area calculations for Pleasant Valley Conservancy savanna areas
Based on tree database. Areas determined from ArcGIS.
Sorted by basal area per acre

Management Unit
Basal area per acre Trees per acre Crown cover, percent (see footnote for method)
Interpretation
2 (South slope)
3.1
0.7
0
Prairie
3 (South slope)
3.5
0.6
0
Prairie
22 (East Basin)
15.6
14.6
13
Prairie
18 (Bur oak savanna)
21.3
8.7
19
Open savanna
12A (White oak savanna)
23.3
~21
Open savanna
Triangle (Remnant savanna)
24.2
30.6
~25
Open savanna
6 (South slope)
26.8
15
24
Open savanna
11D/11A (Remnant savanna)
28.4
13.4
33
Open savanna
14 (Transitional)
32.4
32
~40
Open savanna
10 (Bur oak savanna)
32.7
16.2
31
Open savanna
12B/11B
35
21.1
36
Open savanna
5 (Upper south slope)
37.6
17.1
38
Open savanna
7 (South slope: border between prairie and savanna)
39.1
19.7
42
Open savanna
20 (Border between savanna and woodland)
39.7
37.8
48
Open savanna
21 (Border between savanna and woodland)
40.2
35.8
48
Open savanna
8 (Bur oak savanna)
46.8
23
52
Closed savanna
19B (Edge of north woods)
48.5
26
56
Closed savanna
19CDE (Edge of north woods)
50.3
32.1
59
Oak woodland
13 (Edge of north woods)
55.6
57.8
58
Oak woodland
9 (Upper south slope)
60
21.3
67
Oak woodland
23 (Top of south slope)
66.4
34.8
84
Oak woodland
13A (Edge of north woods)
82.3
80.4
~100
Oak woods
15 (North woods; west)
104.6
68.5
~100
Oak woods
16 (North woods; east)
59
50
~100
Oak woods
17 (North woods)
90.8
71.3
~100
Oak woods

Footnote: Crown cover estimated from the nomograph published by Law, Johnson, and Houf 1994. Technical Brief No. 2. St. Paul, MN. U.S. Dept. of Agriculture, Forest Service, NorthCentralForest Experiment Station. TB-NC-2 Can be downloaded from http://www.treesearch.fs.fed.us/pubs/10999. The input data required were Basal area per acre and tree density per acre. Only trees greater than 10” diameter were measured. This nomograph is only for oak savannas; the data for oak woods were just extrapolations.

 

Typical view of an oak savanna, showing the dappled light and shade regime. Some prairie species are able to thrive in this sort of light situation, but others do not. On the other hand, there are a number of "savanna specialists" that grow best in this sort of environment. See below for details.

 

 

  Some Plant Species in Oak Savanna Areas at
Pleasant Valley Conservancy. This represents aggregate data from the years 2002-2007. Not all species were in every savanna unit.

Oak Savanna Understory Plants In addition to the open-grown oaks, the oak savanna has a characteristic understory flora. These are species that thrive in the sort of light regime created by the open-grown oaks (see photo above). Some of these species may also be present in prairies, and others may also be present in oak woodlands, but there is a whole suite of plants that grow best in the savanna environment. These species are sometimes called "savanna indicator species", and they should be sought out when evaluating a potential oak savanna.

We already had some of these species when we began restoration. From our original species list (before restoration began) I pulled out all the savanna species into a separate list. There were 99 savanna species that we had before restoration began. Some of them were common, others fairly rare. The whole list is available (PDF format) at this link.

Because the open canopy means that light can get to the forest floor, the oak savanna has a wide diversity of grasses and other flowering plants. Because the habitat is so variable, there is more diversity in savanna than there is in prairie. In 2004, 184 species of flowering plants were identified in the oak savanna areas of Pleasant Valley Conservancy. The list to the right, an aggregate of years 2002 to 2007, has 275 species. However, not all species were present in all savanna areas.

Important savanna grasses include silky rye (Elymus villosus), bottle brush grass (Elymus hystrix), ear-leaved brome (Bromus latiglumis), and riverbank or woodland rye (Elymus riparius). Pennsylvania sedge (Carex pensylvanica) is very characteristic of oak savannas.

The most interesting flowering plant in our savanna is purple milkweed (Asclepias purpurascens; see photo below), a state endangered species which only appeared after restoration and controlled burning had begun. Other flowering plants include yellow giant hyssop (Agastache nepetoides), a plant of special concern in Wisconsin; shooting star (Dodecatheon meadii); upland boneset (Eupatorium sessilifolium), a plant considered threatened in Wisconsin; purple (or woodland) joe pye weed (Eupatorium purpureum); Lion's foot (Prenanthes alba); elm-leaved goldenrod (Solidago ulmifolia); and yellow pimpernel (Taenidia integerrima).

A number of the listed species are found only rarely or not at all in prairie or in oak woods. They seem to thrive in the savanna habitat.

Follow this link for a a list which shows which savanna species are also present in prairies, woodlands, or wetlands.

 
   
 
Shooting star (Dodecatheon meadii) flowering in profusion after this savanna was restored. This species remains in a vegetative state for years under the shade of invasive brush and trees. Increased available light after opening up the habitat permits the plants to flourish.  

 

Latin name Common name
Achillea millefolium Yarrow
Actaea alba White baneberry
Actaea rubra Red baneberry
Agastache nepetoides Yellow giant hyssop
Agastache scrophulariaefolia Purple giant hyssop
Agrimonia gryposepala Tall agrimony
Allium canadense Wild onion
Allium cernuum Nodding wild onion
Ambrosia artemisiifolia Common ragweed
Ambrosia trifida Giant ragweed
Amelanchier arborea Juneberry
Amorpha canescens Lead-plant
Amphicarpaea bracteata Hog peanut
Anaphalis margaritacea Pearly everlasting
Andropogon gerardii Big bluestem
Anemone canadensis Meadow anemone
Anemone cylindrica Thimbleweed
Anemone quinquefolia Wood anemone
Anemone virginiana Tall anemone
Antennaria neglecta Field pussytoes
Antennaria plantaginifolia Plantain-leaved pussytoes
Apocynum sibiricum Clasping dogbane
Aquilegia canadensis Wild columbine
Arabis canadensis Sickle pod
Arabis divaricarpa Rock cress
Aralia racemosa Spikenard
Arctium minus Common burdock
Arenaria stricta Sandwort
Arnoglossum atriplicifolia Pale Indian plantain
Asclepias exaltata Poke milkweed
Asclepias purpurascens Purple milkweed
Asclepias syriaca Common milkweed
Asclepias verticillata Whorled milkweed
Asparagus officinalis Asparagus
Aster ericoides Heath aster
Aster laevis Smooth blue aster
Aster lateriflorus Calico aster
Aster novae-angliae New England aster
Aster oolentangiensis Sky-blue aster
Aster pilosus Hairy aster
Aster prenanthoides Crooked aster
Aster sagittifolius Arrow-leaved aster
Aster sericeus Silky aster
Astragalus canadensis Canadian milkvetch
Aureolaria grandiflora Yellow false foxglove
Baptisia lactea White wild indigo
Berberis vulgaris European barberry
Bidens sp. Beggar's tick
Bouteloua curtipendula Side oats grama
Brassica sp Mustard
Bromus inermis Smooth brome
Bromus kalmii Prairie brome
Bromus latiglumis Ear-leaved brome
Calamagrostis canadensis Blue-joint grass
Campanula americana Tall bellflower
Campanula rapunculoides European bellflower
Campanula rotundifolia Harebell
Carex blanda Common wood sedge
Carex eburnii Bristle-leaf sedge
Carex pensylvanica Pennsylvania sedge
Carya ovata Shagbark hickory
Ceanothus americanus New Jersey tea
Celtis occidentalis Hackberry
Circaea lutetiana canadensis Enchanter's nightshade
Cirsium altissimum Woodland thistle
Cirsium arvense Canada thistle
Cirsium discolor Pasture thistle
Cirsium vulgare Bull thistle
Clematis virginiana Virgins bower
Coeloglossum viride Frog orchid
Convolvulus arvensis Field bindweed
Conyza canadensis Horseweed
Coreopsis palmata Prairie tickseed
Cornus racemosa Gray dogwood
Corylus americana American hazelnut
Crepis tectorum Hawk's beard
Cryptotaenia canadensis Honewort
Cuscuta cuspidata Dodder
Cypripedium calceolus pubescens Large yellow lady-slipper
Dactylis glomerata Orchard grass
Dalea purpureum Purple prairie clover
Daucus carota Queen Anne's lace
Desmodium canadense Showy tick-trefoil
Desmodium glutinosum Pointed tick-trefoil
Desmodium illinoense Illinois tick-trefoil
Dodecatheon meadia Shooting star
Echinacea pallida Pale purple coneflower
Echinocystis lobata Wild cucumber
Elaeagnus umbellata Autumn olive
Elymus canadensis Canada wild rye
Elymus hystrix Bottlebrush grass
Elymus riparius Riverbank wild rye
Elymus villosus Silky wild rye
Elymus virginicus Virginia wild rye
Erechtites hieracifolia Burnweed
Erechtites hieracifolia Fireweed
Erigeron philadelphicus Marsh fleabane
Erigeron pulchellus Robin's plantain
Erigeron strigosus Daisy fleabane
Eryngium yuccifolium Rattlesnake master
Erysimum cheiranthoides Wormseed-mustard
Eupatorium altissimum Tall boneset
Eupatorium maculatum Spotted joe-pye weed
Eupatorium perfoliatum Common boneset
Eupatorium purpureum Purple joe-pye weed
Eupatorium rugosum White snakeroot
Eupatorium sessilifolium Upland boneset
Euphorbia corollata Flowering spurge
Festuca subverticillata Nodding fescue
Fragaria virginiana Wild strawberry
Galearis spectabilis Showy orchis
Galium aparine Annual bedstraw
Galium boreale Northern bedstraw
Galium concinnum Shining bedstraw
Galium lanceolatum Lance-leaved bedstraw
Galium tinctorium Stiff bedstraw
Galium triflorum Sweet-scented bedstraw
Gentiana alba Cream gentian
Gentianella quinquefolia Stiff gentian
Geranium maculatum Wild geranium
Geum canadense White avens
Geum triflorum Prairie smoke
Hackelia virginiana Stickseed
Hasteola suaveolens Sweet Indian plantain
Helenium autumnale Sneezeweed
Helianthemum canadense Common rockrose
Helianthus decapetalus Pale sunflower
Helianthus divaricatus Woodland sunflower
Helianthus grosseserratus Saw-tooth sunflower
Helianthus strumosus Pale-leaved woodland sunflower
Helianthus tuberosus Jerusalem artichoke
Heliopsis helianthoides Ox-eye sunflower
Heuchera richardsonii Prairie alum-root
Hieracium aurantiacum Orange hawkweed
Hieracium kalmii Canada hawkweed
Hieracium longipilum Prairie hawkweed
Hippuris vulgaris Mare's tail
Hypericum perforatum Common St. John's-wort
Hypericum punctatum Dotted St. John's wort
Hypoxis hirsuta Yellow star-grass
Kuhnia eupatorioides False boneset
Lactuca biennis Tall blue lettuce
Lactuca canadensis Tall lettuce
Leonurus cardiaca Motherwort
Lespedeza capitata Round-headed bush clover
Leucanthemum vulgare Ox-eye daisy
Liatris aspera Rough blazing star
Liatris cylindracea Dwarf blazing star
Lobelia cardinalis Cardinal flower
Lobelia inflata Indian tobacco
Lobelia siphilitica Great blue lobelia
Lobelia spicata Pale spiked lobelia
Lotus corniculata Birdsfoot trefoil
Lupinus perennis Wild lupine
Lysimachia ciliata Fringed loosestrife
Lysimachia quadrifolia Whorled loosestrife
Medicago lupulina Black medick
Melilotus alba White sweet clover
Melilotus officinalis Yellow sweet clover
Monarda fistulosa Wild bergamot
Muhlenbergia spp Muhly grass
Nepeta cataria Catnip
Oenothera biennis Common evening-primrose
Orobanche uniflora Cancer root
Osmorhiza claytoni Hairy sweet cicely
Osmorhiza longistylis Smooth sweet cicely
Oxalis stricta Yellow wood-sorrel
Oxalis violacea Violet wood-sorrel
Panicum latifolium Broad-leaved panic-grass
Panicum oligosanthes Small-seed panic grass
Panicum virgatum Switch grass
Parthenium integrifolium Wild quinine
Parthenocissus quinquefolia Virginia creeper
Pastinaca sativa Wild parsnip
Penstemon digitalis Penstemon
Phalaris arundinacea Reed canary-grass
Phryma leptostachya Lopseed
Poa spp Blue-grass
Podophyllum peltatum May-apple
Polemonium reptans Jacob's ladder
Polygala sanguinea Field milkwort
Polygala senega Seneca snakeroot
Polygonatum biflorum Smooth Solomon's seal
Potentilla argentea Silvery cinquefoil
Potentilla arguta Prairie cinquefoil
Potentilla norvegica Rough cinquefoil
Potentilla recta Sulfur cinquefoil
Potentilla simplex Old-field cinquefoil
Prenanthes alba Lion's foot
Prunella sp. Self-heal
Prunus americana Wild plum
Prunus serotina Wild black cherry
Prunus virginiana Choke cherry
Pyrus malus Apple
Quercus alba White oak
Quercus macrocarpa Bur oak
Quercus velutina Black oak
Ranunculus abortivus Small-flowered buttercup
Ranunculus acris Tall buttercup
Ranunculus fascicularis Early buttercup
Ranunculus recurvatus Hooked buttercup
Ratibida pinnata Yellow coneflower
Rhus glabra Smooth sumac
Ribes americanum Black currant
Ribes spp Gooseberry
Rosa sp. Rose
Rudbeckia hirta Black-eyed Susan
Rudbeckia triloba Brown-eyed Susan
Sambucus canadensis Elderberry
Sanguinaria canadensis Bloodroot
Sanicula gregaria Black snakeroot
Saponaria officinalis Bouncing bet
Schizachyrium scoparium Little bluestem
Scirpus cyperinus Wool-grass
Scrophularia lanceolata Early figwort
Scrophularia marilandica Late figwort
Scutellaria parvula Small skullcap
Senecio pauperculus Balsam ragwort
Senecio plattensis Prairie ragwort
Setaria faberi Giant foxtail
Silene spp. Campion
Silene vulgaris Bladder campion
Silphium integrifolium Rosinweed
Silphium laciniatum Compass plant
Silphium perfoliatum Cup plant
Sisyrinchium campestre Blue-eyed grass
Smilacina racemosa False Solomon's seal
Smilax herbacea Carrion flower
Solanum carolinense Horse nettle
Solanum dulcamara Deadly nightshade
Solidago canadensis Common goldenrod
Solidago flexicaulis Zig-zag goldenrod
Solidago gigantea Giant goldenrod
Solidago juncea Early goldenrod
Solidago missouriensis Missouri goldenrod
Solidago nemoralis Gray goldenrod
Solidago ptarmicoides Stiff aster
Solidago rigida Stiff goldenrod
Solidago speciosa Showy goldenrod
Solidago ulmifolia Elm-leaved goldenrod
Sonchus spp Sow thistle
Sorghastrum nutans Indian grass
Sporobolus heterolepis Prairie dropseed
Stachys palustris Hedge-nettle
Stellaria media Common chickweed
Taenidia integerrima Yellow pimpernel
Taraxacum officinale Common dandelion
Teucrium canadense Germander
Thalictrum dasycarpum Purple meadow-rue
Thalictrum dioicum Early meadow-rue
Thlaspi arvense Penny cress
Torilis japonica Hedge parsley
Toxicodendron radicans Poison ivy
Tradescantia ohiensis Common spiderwort
Tragopogon porrifolius Salsify
Trifolium pratense Red clover
Trifolium repens White clover
Trillium grandiflorum Large-flowered trillium
Triodanis perfoliata Venus looking glass
Triosteum perfoliatum Tinker's weed
Urtica sp. Nettle
Uvularia grandiflora Bellwort
Verbascum thapsus Mullein
Verbena hastata Blue vervain
Verbena stricta Hoary vervain
Verbena urticifolia White vervain
Veronicastrum virginicum Culver's root
Viburnum lentago Nannyberry
Viola canadensis Tall white violet
Viola pedata Bird's foot violet
Viola pedatifida Prairie violet
Viola soraria Door-yard violet
Vitis sp. Wild grape
Zanthoxylum americanum Prickly ash
Zizia aurea Golden Alexander