Gardeners in warm climates can treat fall, and sometimes even winter, as supplemental growing seasons. But for gardeners who experience hard winters, fall is a great time to get a head start on garden clean-up. We hear a lot about four seasons of interest in the garden, but this rarely applies to perennial plants. Most perennials turn ugly as the temperatures drop.
There are exceptions, of course. Some perennials, like Hellebores, may remain evergreen and can be left standing for interest as well as to fuel the vigor of the plant.
Plants like asters and black-eyed Susan have seed pods that feed the birds and can be left standing through the winter.
It's nice to get your garden in order, in the fall, and any plant that is diseased, infested, or otherwise in poor condition, should certainly be cut back and disposed of, rather than leaving them to over-winter.
However, there are perennials that simply don’t fare well if they are pruned too late in the season. They need the winter protection provided by their fallen leaves, to help them survive. The following list is plants that are best pruned in spring. Consider this listing and the complementary Plants to Prune in the Fall, as guidelines. You will learn what works and what doesn’t, for your own garden.
Suggested Perennial Plants to Prune in the Spring
- Artemisia Most Artemisia don’t like being pruned in the fall. The growth that results is too tender to survive the winter and the dieback is often enough to kill the whole plant. Clean in early spring. (USDA Zones 5 - 9)
- Asters Fall blooming asters have generally been pinched and forced several times throughout the growing season. Once they are finally allowed to bloom, they appreciate being left alone to recuperate, until spring. Several bloom so late into the fall, the question of fall clean-up becomes moot. (USDA Zones 4 - 8)
- Astilbe Astilbe don’t require much maintenance. Fall clean-up is unnecessary and may weaken the plant’s tolerance for cold. Minimal spring clean-up is required. (USDA Zones 3 - 8)
- Basket-of-Gold (Aurinia saxatilis) Although Aurinia fares best and lives longer if sheared back after flowering and not allowed to go to seed, the foliage can be evergreen in mild winters and there doesn’t seem to be any benefit to cutting it back until spring. (USDA Zones 3 - 7)
- Bear’s Breeches (Acanthus spinosus) You may need to cut back old, dying foliage throughout the growing season, but the new healthy growth remaining in the fall could well remain evergreen throughout the winter, depending on weather conditions. (USDA Zones 6 - 10)
- Black-eyed Susan (Rudbeckia fulgida) Although not particularly attractive in winter, the seed heads will feed the birds. (USDA Zones 3 - 9)
- Blue Mist Shrub (Caryopteris) Caryopteris bloom on new growth. Cut back to 6-8 inches in the spring. Newer varieties, especially, can be very sensitive to cold and shouldn't be cut back until buds begin to green. (USDA Zones 5 - 9)
- Butterfly Bush (Buddleia davidii) To lessen winter kill, wait for signs of green at the base and then cut back to 6 - 10 inches. (USDA Zones 6 - 9)
- Butterfly Weed (Asclepias tuberosa) Although Asclepias is a prolific self-seeder and should be deadheaded if dozens of new plants are not wanted, it winters better if the foliage is allowed to protect the crown. (USDA Zones 4 - 9)
- Campanula Most campanulas get sheared back at some point during the summer, to clean up ugly or damaged foliage and encourage another flush of blooming. Fresh basal foliage will result and should be left through winter, so as not to encourage more tender growth in the fall. (USDA Zones 3 - 8)
- Cardinal Flower (Lobelia cardinalis) Although Cardinal Flower likes moist soil, it doesn’t like sitting in cold, wet soil all winter. Leaving the foliage and flower stems in tact protects Cardinal Flower from some of the ravages of winter, so hold off clean-up until spring. At that point, you can trim the damaged areas or simply cut back to the ground. (USDA Zones 3 - 9)
- Coral Bells (Heuchera) They are prone to heaving in soils that freeze and thaw. Leaving the foliage intact helps to mulch the plants through winter. http://gardening.about.com/od/Gardening-Resources/ss/Usda-Plant-Hardiness-Zone-Maps.htm (USDA Zones 4 - 9)
- Cushion Spurge (Euphorbia polychroma) In warmer climates, Euphorbia can actually become a shrub and it’s fine to leave the plant alone until spring and then clean out the dead foliage. In colder climates, simply cut the plant back to its base in the spring. (USDA Zones 4 - 8)
- Delphinium If you’re lucky enough to grow Delphiniums as perennials, remove the flower stalks, but allow the foliage to remain until spring. (USDA ones 3 - 7)
- Dianthus Most Dianthus can remain somewhat evergreen throughout the winter and nothing is gained by cutting back in the fall. They will still need some clean-up in the spring. (USDA Zones 5 - 8)
The following list continues the recommendations of plants that are best pruned in the spring. Remember, any plant that is diseased, infested, broken or otherwise in poor condition, should be pruned in the fall.
- Foamflower (Tiarella cordifolia) Tiarella enjoys the cool days of fall and may remain evergreen throughout the winter. (USDA Zones 3 - 8)
- Foxglove, Perennial (Digitalis purpurea) Since perennial Foxgloves are usually pruned back after flowering and produce a rosette of basal growth, nothing more is needed until a light cleaning in spring. (USDA Zones 3 - 8)
- Fringed Leaf Bleeding Heart (Dicentra formosa / eximia) Although the crowns like to be high enough in the soil to be protected from dampness, the foliage is slight enough to leave for the winter and almost disappears by spring. (USDA Zones 3 - 9)
- Gas Plant (Dictamnus albus) The seed heads of the Gas Plant can look attractive well into fall, but the real reason to cut back in early spring is that the sap that irritates many gardener’s skin is not as pronounced during the plant’s dormant stage. (USDA Zones 3 - 9)
- Gayfeather (Liatris spicata) Liatris is another plant that is more sensitive to cool, wet soil than to cold temperatures. When left standing over winter, the seed heads provide food for the birds and may provide some self-seeding, to make up for any plants that don’t survive. (USDA Zones 3 - 9)
- Geum Geum can remain semi-evergreen throughout winter, so no fall pruning is necessary, especially if you’ve been deadheading and cleaning up dead leaves during the growing season. (USDA Zones 5 - 7)
- Globe Thistle (Echinops ritro) Much like coneflowers, Echinops will respond well to a pruning in July, producing more flowers and sturdier plants that will stand for the winter and feed the birds. The plant’s winter survival seems improved if not cut back hard in the fall. (USDA Zones 3 - 8)
- Heartleaf Bergenia (Bergenia cordifolia) The shiny round leaves ca remain evergreen in mild winters and even cold damaged leaves can remain an attractive bronze color. Clean-up in spring, only as needed. (USDA Zones 3 - 8)
- Hosta Although Hosta foliage gets ugly over winter, some Hosta varieties can be damaged by spring frosts and benefit from the protection of the collapsed foliage. (USDA Zones 3 - 8)
- Italian Bugloss (Anchusa azurea) Much like Amsonia, Anchusa looks better and self-seeds less if sheared back after flowering. Anchusa can be sheared all the way back to the crown since its foliage declines rapidly after flowering. But then allow the plant to recover and don’t cut again until spring. (USDA Zones 3 - 8)
- Joe-Pye Weed (Eupatorium maculatum ) When a plant is bred from a common weed, you can usually assume that it doesn’t need much care to survive. Joe-Pye will bloom well into the fall and then produce fluffy seed heads. You can cut it back if you choose, but it’s not necessary to the plant’s survival. (USDA Zones 2 - 9)
- Lady’s Mantle (Alchemilla mollis) Lady’s Mantle doesn’t really like to be sheared back frequently. Occasional shearing or selective deleafing may be necessary because of sun scorch, but Lady’s Mantle will over winter better if left in tact and cleaned up in the spring. (USDA Zones 4 - 7)
- Lamb’s Ear (Stachys byzantina) There’s no point in trying to clean up Lamb’s Ear for the winter. Let it be and remove winter damage when the leaves perk up in the spring. (USDA 4 - 8)
- Lavender (Lavandula) Many areas have a hard time over-wintering lavender. The problem is more often moisture than cold, but cold is a factor. Don’t prune lavender late in the season, as new growth is extremely cold sensitive. Wait until new growth appears in the spring before removing winter die back. (USDA Zones 5 - 9)
- Lavender Cotton (Santolina chamaecyparissus) As with Lavender above, Santolina needs time to harden before winter. Don’t prune at all, after mid-August and wait until new growth appears in the spring before pruning. (USDA Zones 6 - 8)
- Lupine (Lupinus) Lupines are temperamental, short-lived perennials and they do not enjoy winter. Leave the foliage on for protection and hope for the best come spring. (USDA Zones 4 - 6)
The following list finishes off the recommendations of plants that are best pruned in the spring.
- Mums (Chrysanthemum) Leave the foliage intact to protect the plant’s crown. All the better to let the flowers bloom well into the fall. (USDA Zones 5 - 9)
- Oriental Poppy (Papaver orientale) Poppies appear to be ephemeral, disappearing or declining after the blooms fade. However, a new flush of foliage should emerge and can be left on the plants over winter, to act as a mulch. (USDA Zones 3 - 7)
- Pincushion Flower (Scabiosa columbaria) You can remove the old flower stems, but this plant is so temperamental, leaving the old foliage may be the only way you will know where the plant was, come spring. In warmer areas, where it is hardier, the foliage may be evergreen. (USDA Zones 5 - 7)
- Plumbago (Ceratostigma plumbaginoides) There’s not much left to this plant in winter. But many gardeners like to leave it standing so they’ll remember where it is, since it is late to emerge in the spring. (USDA Zones 5 - 9)
- Purple Coneflowers (Echinacea purpurea) Coneflowers don’t look terribly attractive in winter, but they do attract and feed birds. If you’d like both birds and aesthetics, you can always prune your coneflowers in July and get squat, sturdy plants that will provide seed and remain standing. (USDA Zones 3 - 8)
- Queen-of-the-Prairie /Queen-of-the-Meadow (Filipendula rubra / Filipendula ulmaria) Prairie or meadow, these tall plants almost always flop over before spring and can be cut back in the fall, after blooming. (USDA Zones 3 - 9)
- Red-Hot Poker (Kniphofia) You can trim back the foliage as it begins to decline, but don’t cut it back entirely. The crown is very sensitive to cold and leaving a clump of foliage will help protect it. Trimming by ½ will keep the foliage from completely flopping over and retaining too much moisture around the crown. (Zones 5 - 9)
- Russian Sage (Perovskia atriplicifolia) Like its cousin Lavender, Perovskia doesn’t like to be trimmed back in that fall, because it’s tender growth is too sensitive to cold. Wait until new growth appears in the spring and then cut back to about 6 - 8". If the only new growth is from the base of the plant, the entire top woody section has died back and it can be pruned to the ground. (USDA Zones 5 - 9)
- Sea Lavender (Limonium latifolium) The flowers are held so high on this airy plant that it’s easy to forget the cluster of leaves at the base. Go ahead and forget them. Let them be for the winter and clean-up any die back in the spring. (USDA Zones 3 - 9)
- Sea Holly (Eryngium) It's the rare Eryngium that isn't cut back for drying, but a good deadheading in late summer will encourage a flush of basal growth that will carry the plants through winter. No further fall pruning should be done. (Zones 3 - 8)
- Sedum Many of the tall Sedums can remain attractive throughout the winter, even holding caps of snow on their flowerheads. ‘Autumn Joy’, in particular, holds up very well. The basal foliage appears very early in spring, so Sedum can be one of the first plants you prune in the spring. (USDA Zones 3 - 10)
- Tickseed (Coreopsis) Like Chelone, most coreopsis seem to fare better if allowed to stand during the winter and cleaned-up in the spring. (USDA Zones 4 - 9)
- Turtlehead (Chelone lyonii) Keeping the foliage on until spring seems to improve Chelone’s winter survival. (USDA Zones 3 - 8)
- Valerian, Jupiter’s Beard (Centranthus ruber) To be honest, I don’t have much luck keeping this plant alive through winter. But I’m told that cutting it back to about 6 - 8 inches in late summer and then leaving that new growth over winter, increase the plant’s chance of survival. I’ll let you know. (USDA Zones 5 - 8)
- Wand Flower (Guara) Guara is such a short-lived perennial that allowing the flowers to remain and possibly self-seed may be the only way you’ll see another Guara pop up in the garden next spring. (USDA Zones 6 - 9)
- Willow Amsonia (Amsonia tabernaemontana) Amsonia holds it’s shape better if sheared by about 1/3 after flowering. You’ll lose the seed pods, but you’ll prevent rampant self-seeding. However, after this initial shearing, Amsonia responds better to being cut back in the spring, rather than the fall. Spring pruning seems to rejuvenate it. (USDA Zones 3 - 9