December is the month of festivities, questionable holiday sweaters, and gardens that look like a teen classroom, all messy edges and theatrical sighs.
It is the month of wondering how much of the fading flora you should ruthlessly hack to the ground. Should you tidy up every floppy perennial? Or leave the seed heads waving in a frosty wind?
Somewhatmighty Gardener, this is your guide!
Plants to Cut Back…
When it comes to disease and mushy stems, you’re not aiming for shabby chic but hitting the delete key on last year’s bad decisions.
By the way, if you’re still eyeing those leftover bulbs on your porch, you might not be too late. Here’s what you can still plant in late November and December if you want a last burst of spring color.
1: Peonies, Phlox & Bee Balm (Mildew-Prone Plants)
Right about now, Peonies (herbaceous peonies only!), Garden Phlox, and Bee Balm wallow in self-pity over their damp-rag looks. And worse, they’re sheltering invisible squatters.
The usual suspects, like that trio, simply must finish the growing season covered in powdery mildew. It’s like they’ve been dusted with flour. Yet don’t blame the cat, it’s innocent (this time).
Chop their stems right down to a couple of inches above the ground. Collect and discard every single bit of the affected debris. Do NOT compost it. Yucky fungal spores count on it.
Quick tip: Any branch on any shrub or tree that appears brown or shriveled (or obviously dead) waves a welcome sign for pests and rot. Dead wood never helped anyone, so make it disappear!
Cut the 3D stems (you know, the dead, diseased, or damaged) back cleanly to healthy wood. If rot creeps into the healthy parts of the plant, you’ll turn a small problem into an expensive one. And you need money to buy generic stuff that will come back to you from someone else next year.
2: Apples, Pears & Berry Bushes for Better Harvests
If your fruit tree crowns look too thick, they are too thick. And if they are too thick, the fruits won’t get the sunlight or proper ventilation. Result? Free Halloween decorations next year.
Those in need of this aggressive scheduling are your pome fruits (apples and pears), along with any unruly currants or gooseberries. Thin them in a way that allows light into the center (think about an open wine glass; it helps, even when it’s empty).
Plus, if you grow them, you need to remove all the old, brown raspberry canes that produced fruit this year, as they’ve already packed their stuff, given their notice, and are not coming back. This applies to the spent brown canes, not the new green primocanes!
If you want a full breakdown of which fruit trees respond best to winter pruning, here’s our guide to fruit trees you should prune in December. It’s super helpful if you’re unsure what’s safe to cut right now.
3: Grapevines & Wisteria Before They Start Bleeding
Trigger warning. Prepare to read about Grapevines and Wisteria losing their very life force. About them weeping or ‘bleeding’ excessively after being cut back too late in winter.
Rapid and alarming loss of sap is why waiting is not an option. Thankfully, December is giving you the perfect window to set up their happy ending.
If you’re working through your fall cleanup and aren’t sure what should’ve been cut earlier in the season, here’s my full guide to which perennials you should cut back before winter (and which to leave standing).
Plants NOT to Cut Back!
Welcome to my favorite part of December: the ‘It’s for the birds’ justification section. (Spoiler: It actually is for the birds.)
If you have shrubs that really struggle with winter winds and freezing nights, take a peek at our guide to 9 shrubs you should wrap or protect before winter, it’s a life saver for tender buds.
1: For Wildlife Support
Untidiness here translates to a crucial winter habitat and an emergency grocery store.
So leave the faded heads on plants like Coneflowers, Black-Eyed Susans, and Sunflowers untouched! Dried seeds are a bird feeder you don’t have to refill for finches and other lovely little birds.
Do not prematurely clear out the spent Fennel or Angelica, either. Even if you trim seed heads to reduce self-seeding, keep the hollow stems in place for shelter!
Their tall, dried-out, and hollow stems and foliage provide shelter for the tiny good guys who will eat your aphids in spring. Go team Ladybugs! And team Lacewings!
2: For Bud Protection
One of the plants that design their own winter jackets is the macrophylla variety of Hydrangea, which blooms on old wood. Its old flower heads protect the new flower buds set right below them.
Quick reminder: You can give them a trim later, but only after the season’s last cold snap passes in early spring.
If you grow tender perennials whose crowns struggle in the cold, like Dahlias, you have two options.
I like to dig mine up for winter, but if you overwinter yours in the ground, clear away the soggy leaves that cause rot and let the remaining top growth cushion the tubers against the worst chills.
And if you’re unsure which to lift or leave, here’s our full guide which bulbs actually need lifting before winter (and which are fine staying in the soil).
3: For Aesthetics
While the stiff remains of Sedum are structural scaffolding that prevent the garden from collapsing into brown mud-iocrity, nothing delivers better visual interest than frost-dusted tall Ornamental Grasses.
In the same manner, Evergreens, like Boxwood, Holly, and Juniper, make the perfect backdrop and year-round structure. The only thing required from you is to resist the urge to shear them now.
And if you’re not sure which plants actually benefit from a winter mulch layer, here’s our guide to which plants you should mulch before winter (and which you shouldn’t).
Time to Celebrate Your Tidy-ish Garden
The goal was never a sterile, perfectly neat patch of dirt; that’s for amateurs. The goal was a healthy, functional, slightly mysterious garden. And you’ve delivered.
Now put down the tools, grab a hot beverage worthy of your efforts, binge-watch something terrible, knowing your landscape is securely sleeping under its frosting.
And if you’re in the mood for something fun indoors, here are a few houseplants you can propagate from cuttings in December, it’s my go-to winter project when the garden is too cold to deal with.
