Plant of the Month: Physocarpus opulifolius ‘Diabolo’

Physocarpus opulifolius ‘Diabolo’

If I were limited to just three types of deciduous shrubs for my garden, one of them would be Physocarpus opulifolius ‘Diabolo’® (Ninebark Diabolo). This plant has it all:  fantastic leaf shape and color, lovely arching habit, a multitude of charming pink and white spring flowers followed by small red berries, deep red fall color, and winter interest from its peeling bark. Beyond its physical attractions, ‘Diabolo’ is also incredibly cold-hardy (to Zone 2-3), is not fussy about soil type or pH, is easily pruned to preferred height and shape, and, once established, is comfortable withstanding prolonged dry periods. Ninebark Diabolo can be planted in either sun or partial shade. My shrub is planted in a northern exposure and is flourishing with only afternoon sun.  Additionally, after five years, I have  never noticed a single insect or disease problem. What more could a gardener ask for?

Before we look at specifics, here’s some interesting background from Oregon State University on how the plant was discovered and named:

• “This selection was discovered in June 1968 in a field of 120,000 seedlings of Physocarpus opulifolius.  The discovery was based on the unique red foliage of this particular seedling in the large field planting of typically green foliaged plants in Ellerbek, Schleswig-Holstein, near Hamburg in Germany.  This distinct selection was given the cultivar name ‘Monlo’ in the patent application.    The trademark name of ‘Monlo’ is Diabolo®, which is now owned by Monrovia Nursery.  However, the name often seen in nursery commerce is Diablo, usually, but incorrectly, as the cultivar name, i.e., ‘Diablo’ (note the single quotes which specify the cultivar name).  According to Monrovia’s Brian Jacobs, his company inherited the name Diabolo® from the originator of the plant, Kordes Nursery in Germany.  The word diabolo is derived from the Latin, diabolus, and Greek, diabollos, words for devil, not the Spanish diablo.”

Kordes is a Germany nursery, dating back to 1887, that is famous for its breeding  of hardy, disease-resistant roses.

Physocarpus opulifolius ‘Diabolo’ leaves

‘Diabolo”s most arresting feature is its leaves. The leaves are about 2″-3″ long, crinkled, and trifoliate, with the center section twice the length of the sides. Also notice in the photo below the red stems and the beautiful spring flowers that typically emerge in mid-May (it’s going to be June this year for my plant, due to the cold spring).  Leaves that are in partial shade, or only indirect sun, will be deep green, providing additional visual interest. In fall, the leaves turn from burgundy to deep red.

Ninebark Diabolo flowers and leaves

The plant has a natural arching vase shape, so the only pruning required is for height. If allowed to reach its full height, ‘Diabolo’ can be 10′ tall, with a width of 4′-5′. However, the plant can be easily pruned back anytime after flowering to keep it at 4′-5′ tall. ‘Diabolo’ can also be cut back severely, but this should be done every two years after planting, in order to ensure remaining branches don’t interfere with the plant’s natural shape or sufficient new growth. The lower branches on ‘Diabolo’ tend to weep, so the plant never looks leggy. Consequently, ‘Diabolo’ can be used as a specimen, in a grouping or as a hedge.