Temperatures dropping into the low teens by the week’s end will certainly damage flowers of camellias and the scattered blooms remaining on ‘Eternal Fragrance’ daphnes (Daphne x transatlantica ‘Blafra’, below). With unopened buds, there will typically be some flowers in any spell of mild weather through the winter, though these rarely last for more than a few days until the next freeze. Flowers of late autumn flowering mahonias are unlikely to suffer more than minor damage in the cold.
Already, I see gardens with blue tarps covering evergreens (I presume), and while this protects against damaging winter breezes, it also traps heat that increases temperature variations from a sunny afternoon to nighttime lows. Most always, the garden is best served by leaving well enough alone, though some marginally cold hardy plants will benefit from a thick cover of shredded leaves.
I have inspected hellebores (Helleborus) for signs of swelling flower buds, and ones that have flowered in late December in mild early winters show insignificant bud growth. This is the time when evergreen leaves of hellebores are best cut as low to the crown as possible, when flower buds do not get in the way. Rarely have I gotten around to this simple task, and too often leaves are left that obscure late winter flowers.
After flowering, leaves grow quickly in early spring. Of course, these do not show the hardships of evergreen foliage that has gone through weeks of freezing temperatures, and been covered by ice and snow. Perhaps I will get around to cutting the leaves before December is out, but certainly it will not be done in this week’s cold.