Where to see Dahlias (Jiřinky) in bloom?

It is currently dahlia season. Dendrologická zahrada is the only place I know that has a large collection of dahlias. https://dendrologickazahrada.cz/udalost/jirinky-v-pruhonicich-2024/

Are there other gardens/parks within 2 hour travel distance from Prague where I could see a large collection of dahlias?

Suggestions greatly appreciated!