Winter Pruning Perennials
If you are in the bay area, you know that we are having bizarre weather this year– it has hardly gotten cold since winter began, and we have had some downright hot days, like the day before Christmas when I saw people hiking at the beach in tank tops and daisy dukes. Normally, the perennial pruning should have had already been done last month or even a bit earlier, but here we are in January, and they are still not dormant, or only starting to go dormant. At this point, if you don’t force your perennials to go to sleep, you won’t get the fresh spring foliage, and the plant won’t have enough energy to set flower buds, as it will be trying to keep it’s old, stale foliage alive. Here is a guide on how to prune certain popular ornamental perennials, perennial ground covers, and perennial shrubs. I will group together plants that take similar pruning.
Lavender, Rosemary, Autumn Sage (Salvia gregii), Sticky Monkey Flower:
These shrubby perennials should be sheered in half, from where the foliage begins on the branch to where it ends, so that half of the foliage is retained. After sheering half of the foliage off, trim off the dead branches inside the plant.
Santa Barbara Daisy/Fleabane (Erigeron), Catnip (Nepeta cataria), Plumbago:
Cut back these ground covers all the way to an inch from the ground. Leave the little sticks; they will die back and fall off after the plant recovers in the spring.
Desert Sage/Mexican Sage (Salvia leucantha):
Cut all old, tall, woody, brown stalks to the base of the plant; work around and leave the fresh, short, soft, white stalks.
Bacopa, Lamium, Arctotis, Dianthus, Dusty Miller:
Cut only the branches or stalks that have died back or look spent on these ground covers. For a fresher look, also cut away woody branches that only have a little bit of foliage at the tips.
Snow-in-Summer, Yarrow ‘Terra Cotta’ (Achillea millefolium ‘Terracotta’):
Sheer these groundcovers to the ground. No need to worry about preserving new growth– they will come back from their root base.
Scented Geraniums (Pelargonium only, the plant commonly called Geranium– not true Geraniums such as Johnson’s Blue), Cineraria, Santolina, African Daisies, Rudbeckia, Asters, Fried Egg Plant/Matilja Poppy (Romneya coulteri), Sedum ‘Autumn Joy’, Woodland Sage (Salvia nemorosa), ‘Moonshine’ Yarrow (Achillea millefolium ‘Moonshine’), Carnations, Blanket Flower (Gaillardia):
Cut these perennials back hard to new growth, as low as an inch or two, as long you are leaving the fresh, new growth. Some of these plants have stalks that die back while the new growth springs from the ground– cut back to the base of new growth.
This is the perfect time to cut ferns all the way back to their base, which should be covered in brown, fuzzy, unfurled fiddleheads. No need to leave any leaves at all, which makes for a very fast pruning.
Still to come in the Winter Pruning Series:
Ornamental Grass Pruning
Hydrangea and Rose Pruning
Small Deciduous Tree Pruning