In 2018, we offered the variegated rose of sharon, Hibiscus syriacus ‘Carpa’. Although it sold well, we never managed to offer it again. In the meantime, the plants in our garden have made truly outstanding specimens to 8′ tall x 4′ wide. What we like the most is that it has produced zero seedlings. Many rose of sharon cultivars are horrible reseeders, so we are very careful which ones we allow in the garden.
Hibiscus ‘Carpa’, sold under the trade name, Showtime, comes from Canadian nurseryman Paul Van Der Kroft, who discovered it in 2000, as a variegated sport on the sterile 1800s introduction, Hibiscus ‘Ardens’. The name, Hibiscus syriacus needs a bit of myth-busting. The specific epithet “syriacus” is a bit misleading…first it isn’t from Syria as Linnaeus assumed, but was traded from China via the Silk Road prior to the 1600s. Also, it doesn’t like or need dry soil, since it grows wild along Chinese sea cliffs and streams. I’ve got a feeling you’ll be seeing this back in the PDN catalog before too terribly long.
Zero seedlings? Triploid?
Zero seedlings. Most Hibiscus syriacus are natural tetraploids (four sets of chromosomes). Interestingly, in a 2022 research paper from Oregon State, the three US National Arboretum introductions (Diane, Helena, and Minerva, that are supposedly sterile triploids, turned out to be tetraploids. The also were found to be female fertile, although our 30 year old specimen of Hibiscus syriacus ‘Diane’ has never produced a seedling. Hibiscus ‘Ardens’, the plant that mutated to H. ‘Carpa’ was 100% sterile, even with intentional crossing. It too, tested as a tetraploid.