Cross Pollination in the Home Garden: Planned Parenthood?
Barbara Lewis
Hybrids that appear in the home garden delight some and frustrate others. For those enjoying the “promiscuous process,” surprise hybrids bring special delight. However for those wanting to maintain a steady and reliable supply of species seeds, particularly those members who participate in the APS Seed Exchange, the occurrence of unintended hybrid seeds is a problem.
Being informed (prepared?) can help avoid frustration. Knowing which species are likely to cross is a starter. Knowing how far apart to plant the amorous fellows remains an unanswered question. We hope to build a reliable repository of information on this subject. Please share your knowledge using our Blog, and we’ll add it to this section. In the meantime here are a few starters:
Subgenus Dasanthera commonly produces hybrids; most commonly:
P. cardwellii
P. fruticosus
P. davidsonii
P. barrettiae
P. rupicola
Penstemon Pestemon Proceri
P. confertus and P. peckii
P. confertus and P. euglaucus
Penstemon Penstemon Penstemon
P. calycosus
P. digitalis
Penstemon Cristati
P. cobaea
P. triflorus
Penstemon Peltanthera in gardens where several of the Peltanthera are grown, hybrids are not uncommon; one example:
P. palmeri and P. spectabilis
Habroanthus elmigera
Habroanthus Elmigera may cross within Habroanthus Glabri
Section Coerulei rarely, most commonly
P. grandiflorus and P. murrayanus
Sections Peltanthera and Fasciculus commonly result in the “Mexican hybrids”
Personal Communication from Ginny Maffitt
…hybridization usually occurs between members of a section or subgenus, so that's why members of Dasanthera growing near each other are considered to be producing hybrid seed. Check p. 60 of Bob Nold's "Penstemon" book for this discussion. One exception he mentions is in subgenus Habroanthus, where members of section Glabri and Elmigera will cross, as one if bee and the other hummingbird pollinated.
Collectors considering 2 species in bloom could check to see if they're closely related by looking them up inmost penstemontexts. An easier way is to collect from an isolated plant (other side of the house?).