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Warm and Cool Season Plants

Warm Season vs Cool Season Plants

The terms “warm season plants” and “cool season plants” generally refer to seasonal growing adaptations of non-woody plants like grasses and wildflowers. While the Great Plains has an east-to-west gradient of tallgrasses dominating in the rainier eastern half and short grasses in the dryer western half, there is also a cool-to-warm gradient from the northern half (near and entering Canada) to the southern half (near and entering Mexico). To boot, the growing season can be as short as 100 days in the north and as lengthy as 250 days in the south.

Warm Season

Plants adapted to germinating and growing in warmer temperatures and longer growing seasons dominate the southern latitudes.

Cool Season

Plants adapted to germinating and growing in cooler temperatures and shorter growing seasons  dominate the northern latitudes.

Indiangrass is an example of a warm season plant. 

Bluebonnets are an example of cool season plants. 

The geographic ranges of these plants aren’t fixed in place—in excessively hot years, warm season plants can dominate latitudes further north than usual. And cool season plants dominate cooler-than-usual years in the south. The same is true of seasons:  the hottest days of the year in the north tend to allow warm season plants to dominate while the coolest days of the year in the south allow cool season species to dominate.

BONAP Map of Texas Grama.

There are growing differences even within a single species. This is one reason why planting seeds from your local ecoregion is important! For instance, one species of grama grass stretches across the entire Great Plains range from north to south, and local varieties of it have adapted to their growing seasons. When planted in identical conditions, seeds of this grama from the northernmost part of its range develop three times as fast as seeds from the southernmost part of its range.

In Texas, most grass species are warm season adapted. This makes sense because Texas gets hot for much of the year! Of the 469 native grass species in Texas, 74% (347 species) are warm season species. And while this is true, the remaining cool season species are just as important for sustaining Texas habitats during the cooler months.