2015 Perennial Plant of the Year™ Geranium xcantabrigiense 'Biokovo' Photo: Sinclair Adam
The Perennial Plant Association's Perennial Plant of the Year for 2015 is Geranium xcantabrigiense "Biokovo", and a number of other cultivars of this good landscape and garden species are available in the marketplace as well. "Biokovo" is found growing in Dalmatia region in Croatia. This species was the result of natural crosses occurring about the Mediterranean sea where Geranium dalmaticum and Geranium macrorrhizum, whose naturally occurring populations spontaneously crossed to form this new species. Cambridge University Botanists subsequently repeated the process in the greenhouse to yield a cultivar now named "Cambridge".
Some other good forms are "St. Ola", "Karmina", and "Berggarten". These selections are all good plants for part to full sun areas, and have an evergreen to semi-evergreen character. The foliage is aromatic, and when bruised or crushed gives off a spicy fragrance. That characteristic comes from the parent Geranium macrorrhizum which also has fragrant foliage. These too are good landscape plants and take the heat as well as the cold, as G. macrorrhizum is generally accepted as a staunch zone 3 perennial, and also does well in 6, 7 and 8.
Probably the most popular hardy geranium is G. Rozanne, a hybrid form which has a particularly long bloom period. The bright blue flowers are out on this form from May to frost, and Rozanne spreads as the season progresses. This is a patented cultivar introduced by Blooms of Bressingham, sold in large quantities in PA, and hardy in USDA zones 5-8.
Rozanne was the PPA's Perennial Plant of the Year in 2008. Photo: Sinclair Adam
Some other species well worth considering would be G. wlassovianum, G. sanguineum, and G. phaeum, all hardy to zone 4. The cultivars of G. sanguineum are numerous, but a very short compact one is Max Frei, and one that is almost shrub like in habit is Cedric Morris growing to about 26-28". G. wlassovianum is native to Asia, but thrives in our area, with pubescent foliage that takes on a rich red color in the autumn, and dark purple flowers. This species does well in sun to part shade, providing an interesting contrast in foliage to smooth leaved plants, and is attractive to butterflies as well.
One selection that is very interesting is Geranium "Sirak" which grows happily in zones 5-8. "Sirak" is a hybrid of G. ibericum x gracile and is very attractive to many bee species. This hybrid has large flowers and has received the RHS Award of Merit. A slight controversy has arisen over this plant as it was a cross made by two different breeders in two distinctly different locations. It is also being sold as Geranium x "Karis", as the two forms have been determined to be botanically different by RHS plant judges. "Karis" is a bit shorter than "Sirak" but they are both great plants.
Many more interesting forms of hardy geraniums are being grown by perennial plant producing companies than I have discussed in this article, most do very well in PA and are excellent additions to gardens.