Autumn flowering, hybrid mahonias (Mahonia x media) are a bit late, usually beginning bloom in mid-November, but today showing only yellow through the buds on elongated panicles. I expect buds to open soon, in a few days, but it could be another week. With late autumn flowering, I’m uncertain if it’s cold, heat, or hours of sunlight that influence the timing of flowers. The weather forecast for the next week includes a bit of everything, from twenty to sixty-five degrees, snow and probably short sleeves, but whatever, there should be flowers soon. In any case, once flowering begins, flowering will persist for six weeks or longer unless temperatures drop below ten degrees (F.).
The oldest of the garden’s hybrid mahonias are ‘Winter Sun’ (ten years or longer), with more recent plantings (in the past five years) of ‘Charity’, ‘Underway’, and ‘Marvel’ that are mostly indistinguishable except that ‘Marvel’ has only a single spine at the tip of each leaf. Two ‘Marvel’, most recently planted a year ago, show no signs of imminent flowering, one perhaps the result of excessively damp soil and the other could be too shaded.
Several Leatherleaf mahonias (Mahonia bealei, above) flower in early spring, and already panicles are developing. Occasionally, in a very mild early winter, these will bloom as early as mid-January, and a time or two flowers of autumn and spring bloomers have intersected for a week or two. Another mahonia (‘Beijing Beauty’) flowers unremarkably, with short panicles partially obscured by foliage earlier in autumn, and ‘Soft Caress’ and a few others have proven not to be sufficiently cold hardy.
A year ago, autumn flowering camellias were exceptional early in the season, the best that I can recall, with scattered blooms extending into December. The timing of flowers is later, and more typical this year, and despite regular nighttime temperatures into the twenties new buds open daily (above). Fully opened flowers are damaged by temperatures in the low twenties, so each shrub displays white or pink as well as partially browned flowers. As long as daytime temperatures rise above forty degrees buds will continue to open into January.