Quick answer: 4 native Illinois plants have a recorded bloom range that includes December.
4 species
- Buffalograss Bouteloua dactyloides · 19 states
- Little bluestem Schizachyrium scoparium · 42 states
- Prairie blazing star Liatris pycnostachya · 19 states
- Witch-hazel Hamamelis virginiana · 33 states