There are also several sub-species of H. arborescens, like 'radiata', which produce more ray-flowers than other wild arborescens; and 'di...Read Morescolor' (which has more fertile flowers and may only have a couple showy sepals). Subspecies 'discolor' grows at lower elevations than subspecies 'radiata'. All grow in cool, moist habitats in shade.
In sub-species 'radiata', the upper surface of the leaves has hairs along the veins. The underside of the leaf is more of a silver-white, and covered with a thick fabric of white hairs that microscopically appear woven like a carpet. This sub-species is also not as comfortable in heat or during times of drought, it is also more difficult to root from cuttings.
There are several forms of ssp. radiata in cultivation, like 'Robusta', and 'Spring Grove', which are all listed in the "Hydrangea International Index." And there are other types in cultivation with showy flowers, like 'Samantha' and 'Terry Greer' with mostly sterile flowerheads, more reminescent of non-subspecies like 'Annabelle'.
Zone hardiness in all H. arborescens is 3 to 9 but subspecies radiata should be grown in zone 6 and cooler zones for best chances. Information from "Hydrangeas for American Gardens," by Michael A. Dirr (2004).
This is the wild form with the "flat-top" heads of flower clusters, unlike the rounded ball form. It grows wild around here and is just p...Read Moreretty in the landscape, doesn't take over, but it does spread by runners. I really like this in my gardens, it dies back to ground each year and spring it shoots up again here in my OH garden. (zone5-6)
There are also several sub-species of H. arborescens, like 'radiata', which produce more ray-flowers than other wild arborescens; and 'di...Read More
This is the wild form with the "flat-top" heads of flower clusters, unlike the rounded ball form. It grows wild around here and is just p...Read More