Our oak savannas are an important part of our natural heritage.

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.

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.

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.

The Importance of Fire: Probably the most common reason why the oak savanna community has disappeared is because of the lack of fire. 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 an important fuel of a savanna burn. When oak leaves 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.

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 Although burns are vital, clearing the invasive brush and trees should be done first. 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 completely 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. An open-grown oak is a handsome specimen that 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.

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 lower part of the 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 50% 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 the larger 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 that10 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 the 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 oak woods.

Tree database

In 2008-2011, as one of our winter projects, we set up a database of all the trees at Pleasant Valley Conservancy. Each tree 10 inches in 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.

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.

The ages of some of the oldest bur oaks have been determined by the TREES Laboratory at UW-Platteville. The oldest bur oak found had a start date in 1736, which was in colonial times (reign of King George II). Numerous bur oaks are 200 years old or older.

White oak

White oaks (Quercus alba) are found in four areas. The two areas to the left of 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 areas 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 the right on the map below is very sandy, but the other population is on soils derived from dolomite which is 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

1. Crown cover is 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” in diameter were measured. This nomograph is only for oak savannas; the data for oak woods were just extrapolations.
   
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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 the savanna than there is in the 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.

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

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