Flowering Plants (Forbs) of Oak Savannas

The diversity of forbs in a restored oak savanna is very high, generally higher than in either a prairie or woodland. The reason for this is that the savanna offers both prairie-like and woodland-like areas as well as “true” savanna areas. Thus, in addition to prairie and woodland plants, plants which thrive in intermediate light regimes, savanna specialists, are present. See the work of Stephen Packard.

Savanna Indicator Species

Some of these unique savanna specialists have been called “savanna indicator species.” The list in the table below was developed by a group of experts for the 1995 Midwest Oak Savanna Conference and was collated by Brian Pruka, an ecologist at the University of Wisconsin-Madison.

According to Pruka: “The presence of these light-dependent understory species indicates a recent closure of the canopy. Wooded sites containing sufficient populations of these species, therefore, have the highest potential for recovery if properly managed through the use of prescribed burns, mechanical canopy thinning, and other techniques….[These] are the best indicators of former savannas and open woodlands because they tend to be limited to partial canopy conditions. In more densely-wooded sites, these species are usually in a state of declining vigor due to the ever-increasing canopy closure. They typically persist in densely-wooded sites only near canopy openings such as woodlot edges, roadsides, or brushed utility corridors.”

Oak savanna "indicator" species (Pruka's list #1 )
Latin name
Common name
Agastache nepetoides
Yellow giant hyssop
Agastache scrophularieaefolia
Purple giant hyssop
Anemone virginiana
Tall anemone
Asclepias purpurascens
Purple milkweed
Aster linariifolias
Flax-leaved aster
Astragalus Canadensis
Canadian milkvetch
Aureolaria grandiflora
Yellow false foxglove
Aureolaria pedicularia
Clammy false foxglove
Baptisia leucantha
White wild indigo
Baptisia leucophaea
Cream wild indigo
Besseya bullii
Kitten tails
Blephilia ciliata
Ohio horse-mint
Bromus kalmii
Prairie brome
Cacalia atriplicifolia
Pale Indian plantain
Cacalia muhlenbergii
Great Indian plantain
Camassia scilloides
Wild hyacinth
Castilleja occinea
Indian paintbrush
Ceanothus americana
New Jersey tea
Ceanothus ovatus
Prairie redroot
Cirsium altissimum
Woodland thistle
Convolvulus spithamaeus
Low bindweed
Cypripedium pubescens
Large yellow lady-slipper
Desmodium canadense
Showy tick-trefoil
Dodecatheon meadia
Shooting star
Elymus villosus
Silky wild rye
Elymus virginicus 
Virginia wild rye
Erigeron pulchellus
Robin's plantain
Eupatorium sessilifolium
Woodland boneset
Gentiana alba
Cream gentian
Heuchera americana
Prairie alum-root
Hieracium candense
Canada hawkweed
Hypoxis hirsuta
Yellow star-grass
Krigia biflora
False dandelion
Lilium philadelphicum
Prairie lily
Lysimachia lanceolata
Lance-leaved loosestrife
Lysimachia quadrifolia
Whorled loosestrife
Oenothera perennis
Small sundrops
Oxalis violacea
Violet wood-sorrel
Pedicularis canadensis
Wood betony
Penstemon gracilis
Slender beard-tongue
Phlox pilosa
Prairie phlox
Polemonium reptans
Jacob's ladder
Polygala senega
Seneca snakeroot
Polytaenia nutallii
Prairie parsley
Prenanthes alba
Lion's foot
Ranunculus fascicularis
Early buttercup
Ranunculus rhomboideus
Prairie buttercup
Silene stellata
Starry campion
Solidago hispida
Hairy goldenrod
Taenidia integerrima
Yellow pimpernel
Tephrosia virginiana
Goat's rue
Thaspium trifoliatum
Meadow parsnip
Tomanthera auriculata
Eared false foxglove
Triosteum aurantiacum
Late horse gentian
Triosteum perfoliatum
Early horse gentian
Veronicastrum virginicum
Culver's root
Zigadenus elegans
White camas
Zizia aurea
Golden Alexander


Photos of some savanna "indicator" species
Giant yellow hyssop
Purple milkweed
Canada milk vetch
Yellow false foxglove
New Jersey tea
Canada tick trefoil
Shooting star
Cream gentian
Jacob's ladder
Lion's foot
Culver's root
Golden Alexander
Henderson list of Wisconsin Savanna Specialists

In his review of oak savanna communities of Wisconsin, Richard Henderson presented a smaller of characteristic savanna specialists for Wisconsin, some of which are also listed above.
Latin name Common name
Arnoglossum atriplicifolium Pale Indian plantain
Asclepias purpurascens Purple milkweed
Besseya bullii Kitten tails
Camassia scillioides Wild hyacinth
Ceanothus americanum New Jersey tea
Cirsium altissimum Woodland thistle
Elymus villosus Silky rye
Eupatorium sessilifolium Upland boneset
Gentiana alba Cream gentian
Lespedeza virginica Slender bush clover
Solidago ulmifolium Elm-leaved goldenrod
Taenidia integrifolium Yellow pimpernel
Triosteum perfoliatum Tinker's weed


The John Curtis Savanna List of Prevalent Savanna Species

In his extensive research on the vegetation of Wisconsin, John Curtis measured the relatively frequency of the groundlayer forbs and grasses in a number of oak savannas. These data are given in the table below, sorted by average frequency. The Curtis list gives the average data for a number of southern Wisconsin oak savannas, whereas the Pruka list is based on knowledge by a group of experts.

Latin name
Common name
Average frequency % Presence %
Amphicarpaea bracteata
Hog peanut
41.1 79
Euphorbia corollata
Flowering spurge
34.3 89
Amorpha canescens
33.8 79
Galium boreale
Northern bedstraw
33.2 79
Poa pratensis
Blue grass
27.9 53
Monarda fistulosa
Wild bergamot
23.1 84
Rosa sp.
22.5 84
Heliopsis helianthoides
Ox-eye sunflower
22.1 42
Cornus racemosa
Gray dogwood
21.8 79
Corylus americana
American hazelnut
20.8 68
Apocynum androsaemifolium
Spreading dogbane
19.5 68
Andropogon gerardii
Big bluestem
19.4 68
Desmodium glutinosum
Pointed tick-trefoil
18.7 58
Geranium maculatum
Wild geranium
15.5 68
Lithospermum canescens
Hoary puccoon
14.6 68
Coreopsis palmata
Prairie tickseed
14.4 63
Fragaria virginiana
Wild strawberry
13.5 68
Helianthus strumosus
Pale-leaved woodland sunflower
13.3 47
Dalea purpureum
Purple prairie clover
12.7 63
Rhus radicans
Staghorn sumac
12.5 58
Helianthus pauciflorus
Prairie sunflower
12.3 32
Schizachyrium scoparium
Little bluestem
12.2 58
Galium concinnum
Shining bedstraw
12.1 42
Smilacina racemosa
False Solomon's seal
12.1 79
Vitis riparius
Riverbank grape
11.6 79
Comandra umbellata
False toadflax
11 84
Panicum leibergii
Prairie panic grass
10.9 58
Ceanothus americanus
New Jersey tea
10.3 63
Viola pedata
Bird's foot violet
8.6 63
Stipa sp
Needle grass
8.5 58
Carex pensylvanica
Pennsylvania sedge
8.4 32
Rhus glabra
Smooth sumac
8.4 53
Aralia nudicaulis
Wild sarsaparilla
8 42
Lespedeza capitata
Round-headed bush clover
7.9 47
Antennaria neglecta
Field pussytoes
7.8 53
Parthenocissus vitacea
Virginia creeper
7.6 53
Anemone cylindrica
Prairie thimbleweed
7.5 58
Viola cucullata
Common violet
5.8 42
Smilax herbacea
Carrion flower
5.6 37
Helianthus occidentalis
Western sunflower
5.3 37
Aquilegia canadensis
Wild columbine
4 37
Polygonatum biflorum
Smooth Solomon's seal
3.8 53
Physalis virginiana
Lance-leaved ground-cherry
3.2 37
Prenanthes alba
Lion's foot
3.2 47
Phlox pilosa
Prairie phlox
3 42
Asclepias syriaca
Common milkweed
1.3 37
From Curtis Table XVI-2. The data have been sorted by average frequency, with the most frequent at the top. Presence means
the percentage of sites where the species was found.
Brian Bader’s species lists

A much more extensive set of species lists has been developed by Brian Bader, based on observations from the University of Wisconsin-Madison Arboretum. This list is very extensive and includes shrubs as well as forbs and grasses. Also, the species are categorized as far as preferences for full sunlight, partial sunlight, partial shade, or full shade.
Bader’s lists are very useful for detailed restoration work, and can be downloaded here as a PDF version.
Ecology of savanna understory plants
A major activity in any savanna restoration is the recovery of the understory vegetation. Depending upon the history of a site, its understory may be rich in species, impoverished, or absent. The next section will deal with the ecology of savanna forbs and grasses, and the significance of this knowledge for managing a savanna restoration.

Packard, S. 1988a. Just a few oddball species: restoration and rediscovery of the tallgrass savanna. Restoration & Management Notes 6:130-24.
Pruka, Brian. 1995. Midwest Oak Savanna Conference.
Curtis, John T. 1959. The Vegetation of Wisconsin. University of Wisconsin Press, Madison

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