Christmas boxes through the Garden

While most gardeners are quite familiar with boxwoods of the genus, Buxus, far less are familiar with their close cousins, sweet box of the genus Sarcococca. Sarcococca is a small genus of only 15 species of small woody evergreen shrubs, ranging from the Western Himalayas to Thailand, with one long lost family member that resides in Guatemala/SW Mexico.

Unlike boxwoods, which most folks enjoy for their more formal shape, sweet boxes are prized for being less formal in appearance. The unifying characteristic of the evergreen genus is that they flower in winter, with small, but sweetly fragrant white flowers. Our garden is deliciously sweet now in December, as the sweet boxes perfume the air. Sarcococca is a woodland plant, with a wide range of garden soil tolerances from slightly moist to quite dry, but always well-drained.

Sarcococca hookeriana, which ranges natively from Central China to Tibet, is probably the most widely grown species. It is taxonomically divided into two varieties, var. digna and var. humilis. Sarcococca hookeriana var. digyna can top out at 5′ tall, while var. humilis is much shorter, maxing out at 2′ tall. With both subspecies, most of the commercial selections that have been made, are dwarf forms, so height isn’t a reliable way to know which subspecies you’re growing. Sarcocca hookeriana var. humilis ‘Sarsid1’ below is the most compact form we’ve seen, making a 6″ tall mat.

Sarcococca hookeriana var. digyna ‘Purple Stem’ is an introduction from the UK’s Hilliers Nursery. For us, it makes a 4′ wide patch of 18″ tall stalks in 10 years.

Sarcococca ‘Winter Gem’ (below) is a hybrid between both subspecies of S. hookeriana, created by UK plant breeder, Peter Moore.

Sarcococca orientalis hails from below 3,000′ in southeast China, where it can be found along woodland streams. In the garden, our ten year-old specimens are now 3.5′ tall x 3.5′ wide. The green stems are clothed with 3″ long glossy green leaves and adorned with small but insanely fragrant white flowers, starting for us in mid-December and continuing through March…the longest flowering period of any sweet box we’ve grown. Most interesting is that the glossy, black, blueberry-sized fruit from spring persist alongside the winter flowers.

Sarcococca ruscifolia var. chinensis has long, lanky branches to 6′ tall, in comparison to the compact form of the other species above. It’s unique for its red fruit, instead of the black fruit in most other species.

Because there is little else blooming in the winter, pollinators easily travel from plant to plant, so if you have more than one species of sweet box in flower, there is a pretty good chance that the offspring will be hybrids. We raised seed from Sarcococca ruscufolia var. chinensis, and got this compact hybrid, that almost certainly crossed with Sarcococca orientalis.

My favorite species to use as a landscape designer is Sarcococca saligna. Sadly, it gets clobbered in winters where the temperatures drop below 12 degrees F, although it does eventually resprout from the ground.

Sarcococca wallichii, which naturally ranges from India to Yunnan, China, forms an open shrub with 3′ long stalks.
We weren’t sure this would survive here, and while some accessions have not proven winter hardy, this form below from the US National Arboretum has thrived since 2015

One of the most interesting, and a good commercial plant is Sarcococca x confusa. Although this has never actually been seen in the wild, it was finally discovered to be a hybrid between Sarcococca hookeriana var. digyna and Sarcococca ruscifolia var. chinensis. One parent has red fruit, while the other parent has black fruit, so seedlings can range from one color to the other and everything in between. Our oldest clone has reached 3.5′ tall x wide.