My suggestion would be to pot some up and put them in the shade until they recover. I have never dug up a S. penstemonoides up. Being on the endagered species list due to
a flood destroying the population out in the Hillcountry (1200
individuals).
I would do everything I can to save them.
Art

They are well represented in gardens in Texas and around now. I see them in stores all the time and I see them being sold on line in many nurseries. I think they are not endangered in gardens but very endangered in the wild. I saw one growing in a crotch of a tree down by a stream in Wimberley Texas. I thought it was a strange cardinal plant but realized years later it was a S penstemonoides growing in the wild.I have not moved mine either.

Mara:
How have you been ? Where in Wimberly did see it growing out
of a tree? I have done lots of Plant collecting in that area.
I have seen S.penstemonoides at 2 populations the I-10 on
Fredricksberg Creek population and the one that was on the same creek in Lost Maples State Natural area. They both got
wiped out in the flood. Dan Hosage who located the I-10 population waiting on Styrax plantanifolius seed to ripen.
Dan starting growing S.penstemonoides at his place in San Marcos but he did not have any escape in the wild because
of so many deer. I have seen S.roemeriana growing out of boulders, hillsides etc.. in creek beds around Wimberly.
They have some ice forms of S.farinacea around town and
along some areas of Ranch Road 12. A few small populations
of S.azurea var grandiflora on R.R.12 and in Driftwood Tx . Above (and in the area of) Aquarena Springs was a nice population of S. ballotaeflora.
How is your population of S.engelmannii holding up in the Drought?

Art