The genus Penstemon in the family Scrophulariaceae comprises over 250 species, distributed throughout North America and extending southward from Alaska to Guatemala. It is the largest genus of flowering plants endemic to this continent. We only intermittently list a good range of species, depending on whether we or others have been collecting widely in western North America late in the season. Even if we have not collected seeds ourselves, we usually have a few species collected by Californian friends, like John Andrews and Greg Greger. Our seed-bank contains a selection of many of the most outstanding western species collected over recent years. In the opinion of many, seven-year old seed gives the best germination. Jim Almond in the UK has experimented successfully with some of our older Penstemon collections and we believe any species from which we distribute seed collected prior to the current year will still be perfectly viable. Norman Deno has done a lot of work on germination of Penstemon and, as a general rule, it may be assumed that almost all the species we list are plants which will germinate at a low temperature. Sowing from early winter through to early spring should be successful. Like all dry-climate species, germination can sometimes be irregular and it is sometimes fairly sparse, especially with freshly collected seeds. Freezing the seed containers outside might help.

With very few exceptions, the species we offer are from areas with warm, dry summers and cold, dry winters. Few can be easily grown outside in climates such as that of the UK, where summer rainfall is high and winters wet. We have difficulty convincing British growers that these species need the absolute opposite to the conditions suitable for the marginally hardy hybrids, widely grown in the UK These hybrids are mainly derived from a few Mexican species, which are plants from a summer rainfall area and are far from typical of this diverse genus. Unless otherwise instructed, UK gardeners should give all the ones we list as much sun as possible in as well-drained a site as possible.

Obviously for growers in northern Europe, the dwarfer species might be more manageable in raised beds, rock gardens or the alpine-house. The heath-like or thyme-like, mat-forming species in Section Caespitosi have been very successful in the UK under such conditions. The dwarfer members of Section Cristati are also potentially desirable alpine-house plants, though many are proving challenging to grow. Many of the better-known and easier rock-garden species are in Section Erianthera and Section Saccanthera, which are most numerous in the Pacific Coast states, though a few extend eastwards into Montana and Utah. The western ones are likely to be easier to grow both in the Pacific North-west and in northern Europe than the more eastern ones. Though we seldom list more than a few representative collections of Section Penstemon, in general a group of less horticultural value, there are still some good things here and the mountain plants should give little trouble.

The taller species in Section Spectabiles, Section Gentianoides and so on are among the most sumptuous of herbaceous perennials but most are essentially desert plants, which, though temperature hardy, need very sunny, dry conditions to thrive. Remember that this is very much a genus of the intermountain area, where 104 species make their home. There are 63 species listed for Utah with 29 in the Uintah Basin alone. The last, comparatively small, area is the centre of diversity for the entire genus. The species which we list will usually be typical of this genus. The Mexicans, eastern woodlanders and the hybrids are the exceptions.

Nomenclature : We have followed the nomenclature of Noel Holmgren (in the 'Intermountain Flora' and ‘The Jepson Manual’) and Elizabeth Neese (in 'A Utah Flora'), all modern accounts. These two authorities only disagree on a very few minor pounts. Holmgren's classification into sections, as quoted above, is possibly the most recent and arguably the best account of the division of the genus but we have included the names of the divisions used by Bob Nold in his gardeners account, where these differ. These are mainly derived from David Keck’s work and are adopted by Nold, as they are the divisions used by the American Penstemon Society, so are more familiar to American growers. The appropriate section for each species is given in the description field to give some indication of the plant's affinities. This may be helpful regarding cultivation.

Further information : There is only one book for the serious enthusiast. This is the really excellent ‘Penstemons’ by Robert Nold (Timber Press, 1999). Bob Nold knows this genus well both in the wild and in cultivation in his Colorado garden. There is a useless British book, purporting to deal with this genus. It should be ignored, unless you are only interested in tender hybrid bedding plants.