The Upper Midwest US forest-savanna transition is a temperate ecoregion of the Upper Mississippi River basin spanning Minnesota, Wisconsin, Iowa, and Illinois (extending into Michigan and parts of Ontario and Manitoba), marking the meeting ground between eastern deciduous forests and the tallgrass prairies to the west. Its signature landscape is oak savanna of scattered bur, white, and pin oak over bluestem grasses and prairie forbs, grading into maple-basswood and floodplain forests. The climate is humid continental (Köppen Dfa/Dfb). Fire historically kept the savanna open; with settlement and the end of burning, plus conversion to agriculture, less than 5% of habitat remains intact. The unglaciated Driftless Area shelters rare relicts on cool algific talus slopes.

At a glance

About the temperate broadleaf & mixed forests biome

Four-season forests of deciduous hardwoods — oak, maple, beech — often mixed with conifers, shaped by warm summers and cold winters. Trees leaf out in spring and color in autumn; the generally fertile soils have made these forests heavily settled and farmed.

National refinement sub-regions

Catalog plants suited to this ecoregion

Computed from each plant's stated USDA zone range against this ecoregion's USDA Plant Hardiness Zone Map 2023 (1991-2020 climatology) via ArcGIS FeatureServer published current zone range, with the CHELSA mid-century warming delta applied for the projection. Plants whose stated range falls outside both the current and projected zone end up dropped; the rest land in one of the three buckets below.

Collections for this ecoregion

Curated multi-plant collections whose members all fit this ecoregion's zone range — no won't-grow members smuggled in. Overall fit class shown per collection is the weakest link across its members.

Related ecoregions