Paul Rothrock 
The Genus Silphium: 

Native 
Plant 
Profile 

Cup-plant (above) 
and rosinweed 
have profusely leafy 
stems and look more 
sunflower-like. 
By Josh Randall 
If you have visited a remnant tallgrass 
prairie or prairie restoration in northwestern 
Indiana, you likely are familiar with the 
genus Si/phium (family Asteraceae). Several 
species are notable for their exceptional 
height amidst the sea of grass and their 
bright, sunflower-like inflorescences. These 
charismatic Summer perennials include 
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prairie-dock (Si/phium terebinthinaceum), 
compass-plant (S. /aciniatum), cup-plant 
(S. perfoliatum), and entire-leaf rosinweed 
(S. integrifolium). The genus Silphium is 
composed of two subgenera, distinguished 
by their growth habit: either rosettes of large 
leaves and taproot systems or sunflower-like 
16 + Indiana Native Plant Society - Summer 2021 
shoots with fibrous root systems (Clevinger & 
Panero 2000). Both groups have tough (i.e., 
scleromorphic) leaves. 
Prairie-dock (unrelated to true docks 
[Rumex]) has huge triangle shaped leaves 
growing directly from the plant’s base. The 
equally large leaves of compass-plant are 
deeply divided and curiously tend to orient 
themselves vertically with the leaf edge aimed 
southward. In both species the tough leaves, 
with their thick veins and strong petioles, 
ensure the plant can survive the harsh 
drought-like conditions the prairie may offer 
during the summer. As a result of their large 
storage roots, prairie dock and compass-plant 
are well adapted to stressful environments 
that include frequent natural fires. When 
about to flower, these species bolt, pushing 
their inflorescences above the surrounding 
vegetation to a height of up to 10 feet. 
Cup-plant is likely to become the most 
famous member of this genus as the biofuel 
industry mines its potential for bountiful 
cellulose, the structural molecule that 
supports its huge height and strong leaves. 
Cup-plant grows tall leaf stems throughout 
the season. The “cups” that surround the 
main stem are expanded leaf bases that 
hold water following rains. While still a very 
tough looking plant, you may find this species 
growing in moist habitats. 
Entire-leaf rosinweed is the least tough 
Silphium common to Indiana prairies. It is 
often confused for a wild sunflower due to 
its thinner stems and leaves. The name 
rosinweed is a reference to the resinous fluid 
that several members of this genus excrete 
after being damaged. Similar to the latex of 
milkweeds (Asclepias), this fluid has evolved 
as a strategy to reduce herbivory. 
In addition to being a beautiful sign of prairies, 
the genus Si/phium tells an interesting story 
of evolution from dry habitat to wet habitat, a 
scenario that is not very common in plant life 
histories (Crisp et al. 2009). These jumps are 
important to understand as climate change and 
habitat loss will result in a mix of species loss 
or successful adaptation, especially in already 
vulnerable habitats such as the forest-prairie 
transition of western Indiana. 
