Plant Materials
Silphium integrifolium seeds were collected from 12 prairies in
2017 and 2018 (Figure 1; Table 1). The prairie remnants collected
spanned from central Kansas to central Illinois. The prairie remnants
have variable historical, geographic, and climatic characteristics
described in Cassetta et al 2023. From each of the 12 prairies,
seeds were collected from approximately 40 mother plants randomly chosen
from throughout the prairie remnant. As S. integrifolium is an
obligate outcrosser, seeds collected from a single mother were a half
sibling family.
S. integrifolium seeds were germinated at room temperature
together in a heated greenhouse at The Land Institute, Salina KS in
2019. A total of 96 genets comprising eight individuals from each
prairie remnant from different mothers were selected from the seedlings.
Selection of the 96 individuals was randomized although the seedlings
chosen had to be moderately vigorous. The pots containing the seedlings
were randomized and placed on greenhouse benches. Pots were
re-randomized several times during the season. The plants grew rapidly
but remained as vegetative rosettes. Each crown (genet) was divided into
4 pieces (ramets) with approximately equal numbers of dormant buds and
roots, although a few crowns were too small and only produced 2-3
pieces. The ramets were repotted into 10-gallon fabric planters (Smart
Pot) using Pro-Mix BX.