What size container is needed for one penstemon?
Certified GKH Gardening Expert
Pot size will depend on the size of perennial plant that you start with. If you purchase a starter pot--example a 4 to 5 inch pot size, you can go ahead and plant the Penstemon in a 8" pot.
You can sometimes locate larger potted Penstemon and you would pot up them about 1 size larger then the existing greenhouse pot.