The entry for this plant is somewhat misleading. Hibiscus 'Tosca' is a hybrid between our native Hibiscus paramutabilis and Hibiscus syr...Read Moreiacus, possessing features from each parent. I first bought 'Tosca' and 'Lohengrin' at the same time from Glasshouse works about 13 years ago. I planted them in a spot expecting growth similar to H. syriacus, which is a slow grower in my heavy clay soil. By their third summer both 'Tosca' and 'Lohengrin' were over twelve feet tall and at least six feet wide, overwhelming all their neighbors. So I cut them both down to 2' stumps with the intention of letting them grow back in a more controlled manner. 'Tosca' did not appreciate this treatment and the stump died. Fortunately, taking after its H. paramutabilis parent, the plant sends up the occasional sucker and so I moved one of those to a different location. Ten years later that sucker is now a small thicket of several plants that are at least 15' tall with about an 8' spread. I do prune 'Tosca' to discourage horizontal branching but I don't do anything to control the height. The flowers are much larger than either parent, rivaling the tropical H. rosa-sinensis in size. 'Tosca' is self-dead heading and it has never set seeds. The reason I cut back any horizontal branches is because such branches are fully leafed out and then start to bloom they get too heavy to hold themselves up. If I had a larger yard I wouldn't mind having a row of 'Tosca.'
The entry for this plant is somewhat misleading. Hibiscus 'Tosca' is a hybrid between our native Hibiscus paramutabilis and Hibiscus syr...Read More