The when and how of pruning perennials

 

Are you confused as to when and how to prune your perennials in your garden?  Follow these simple instructions and guidelines to make the task easier.

FALL 

fall cleanup should include removal of any dead or diseased foliage. Any cleanup you get done in fall makes for less work in the spring and prevents the spread of disease.  Water plants well, especially evergreens, before the ground freezes to ensure they are well hydrated over the winter.  Fall is a good time to add compost around your plants to improve the quality of your soil, especially clay soil.  Mulch can also be added in the fall, preferably after the ground freezes.

anemones:  cut back after frost

daisies: cut back to 6 inches in fall.  

geraniums (perennial):  cut back if frost turns leaves mushy, otherwise leave foliage on over winter.

grasses (ornamental):  can be cut back to ground in fall or left intact over winter.  If left, cut back first thing in spring, before new growth appears.

hemerocallis/daylilies: remove dead leaves or cut back whole plant to 4 inches.  Although these do not have to be cut back in the fall, it will prevent messy/slimy cleanup in spring.

iris (bearded): cut plants back to 6 inches after frost to prevent disease.  Overgrown clumps should be separated in late summer or early fall.

ligularia: remove leaves when frost turns them mushy

monarda/beebalm:  cut plants back to 6 inches to prevent mildew

peony:  cut plants back to 8 inches to prevent mildew

phlox (tall): cut plants back to prevent mildew

poppy:  leave foliage over winter for protection.  Move or divide in August only

queen of prairie/filipendula: cut back in fall after blooming

salvia:  cut back to 8 inches in fall

sunflowers/helianthus:  cut back to 8 inches in fall

AFTER BLOOMING

some plants just need deadheading (removing dead flower heads), others need the long flower stalks removed. Others require shearing back the plant by half of its size. Each of these techniques improves the appearance of the plants and sometimes promotes reblooming…

achillea:  cut flower stalks back to base after blooming

artemsia:  although they do not flower, cut back plant mid May and late July to prevent flopping

asters:  cut back to 12 inches after blooming in fall

astrantia major/widows’ tears: shear back after flowering to promote reblooming.  Leave foliage on for winter protection

campanula/bellflower: cut flower stalks back to base of plant after blooming

coreopsis/tickseed:  shear off flower stems after blooming

daisies:  remove dead flower heads after blooming to promote rebloom

delphiniums: cut flower stalks back to base after blooming

dianthus/sweet william: shear plant back after blooming

digitalis/foxglove: cut back flower stalks to base of plant after blooming

euphorbia:  cut plant back after blooming to prevent flopping

gaillardia/blanket flower: cut flower stalks back to base of plant after blooming

geraniums (perennial): remove flower stalks after blooming to base of plant to promote rebloom

globe thistle/echinops: cut back late July to promote rebloom

hemerocallis/daylilies: remove flower stalks after blooming

hostas: remove flower stalks after blooming

iris (bearded): cut back flower stalks after blooming

lavender:  cut back flower stalks after blooming to promote rebloom

monarda/beebalm:  cut flower stalks after blooming to promote rebloom

peony:  cut off flower stalks after blooming.

phlox (border): shear back after blooming.  Do not cut back in fall.

poppy: plants go dormant after blooming.  Leave foliage over winter for protection

rudebekia/black eyed susans: deadhead after blooming if desired, do not cut back

salvia: shear back after blooming to promote rebloom

sedums:  cut back both fall blooming and ground cover sedums after flowering.  Flower heads can be left on the fall blooming variety if desired for winter interest.

 SPRING

wait until soil is no longer soggy to avoid compacting it or damaging bulbs, but don’t wait too long.  April is usually best in our zone 4-5 area of Ontario.  If plants looks green and healthy, leave them alone. A light cleanup involves removing dead/brown leaves and stems only.

astilbe: foliage protects plant over winter,  needs light cleanup in spring only

bergenia: needs light cleanup in spring only

campanula/bellflower:  cut plant back in spring.  Cut flower stalks after blooming to base of plant

clematis (most): deadhead spent flowers, cut plant back to 6 inches in spring

coreopsis/tickseed:  cut plant back to 6 inches in spring. Shear off flower stems after blooming

crysthanthemums/mums: foliage protects plant over winter; cut plant back in spring.  Remove faded flower heads after blooming

delphiniums: cut plant back in spring. Cut back flower stalks to base of plant after blooming

diantus/sweet william: foliage protects plant over winter, cut back plant in spring

digitalis/foxglove: requires light cleanup in spring only. Cut flower stalks to base of plant after blooming

echinacea and other coneflowers: deadhead after blooming if desired, only requireslight cleanup in spring

globe thistle/echinops: requires light cleanup in spring only, do not cut back in fall

grasses (ornamental):  if not cut back in fall, cut back to ground BEFORE new growth appears in spring

heuchera/coralbells: leave foliage over winter, requires light cleanup only in spring 

hosta: leave foliage over winter, cut back flower stalks after blooming

hydrangeas:  peegee, annabelle and snowball varieties can be cut back to 12 inches if overgrown

iris (bearded): remove dead leaves to prevent disease.  Can be divided in spring if did not bloom previous spring.

iris (siberian): foliage protects plant over winter, cut back in spring to 4 inches

joe pye weed: no maintenance required

lady’s mantle: light cleanup in spring only

lambs ears: light cleanup in spring only

lavender:  do not cut back in fall, wait until new growth appears in spring to remove winter kill.  Shear flower stalks back after blooming to promote rebloom

liatrus/gayfeather: light cleanup in spring only

lupines: foliage protects plant over winter, light cleanup in spring 

red hot poker: foliage protects plant over winter, light cleanup in spring

russian sage: cut back to 6 inches in spring, only after new growth appears

sedum (fall blooming): cut back to 6 inches in early spring if not done so in fall

AFTER BLOOMING 

some plants just need deadheading (removing dead flower heads), and some need the entire flower stalks removed. Others require shearing back the plant by half of its size. Each of these techniques improves the appearance of the plants

achillea:  cut flower stalks back to base after blooming

artemsia:  although they do not flower, cut back plant mid May and late July to prevent flopping

astrantia major/widows’ tears: shear back after flowering to promote reblooming.  Leave foliage on for winter protection

campanula/bellflower: cut flower stalks back to base of plant after blooming

coreopsis/tickseed:  shear off flower stems after blooming

daisies:  remove dead flower heads after blooming to promote rebloom

delphiniums: cut flower stalks back to base after blooming

dianthus/sweet william: shear plant back after blooming

digitalis/foxglove: cut back flower stalks to base of plant after blooming

euphorbia:  cut plant back after blooming to prevent flopping

gaillardia/blanket flower: cut flower stalks back to base of plant after blooming

geraniums (perennial): remove flower stalks after blooming to base of plant to promote rebloom

globe thistle/echinops: cut back late July to promote rebloom

hemerocallis/daylilies: remove flower stalks after blooming

hostas: remove flower stalks after blooming

iris (bearded): cut back flower stalks after blooming

lavender:  cut back flower stalks after blooming to promote rebloom

monarda/beebalm:  cut flower stalks after blooming to promote rebloom

peony:  cut off flower stalks after blooming.  

phlox (border): shear back after blooming.  Do not cut back in fall.

poppy: plants go dormant after blooming.  Leave foliage over winter for protection

rudebekia/black eyed susans: deadhead after blooming if desired, do not cut back 

salvia: shear back after blooming to promote rebloom

Good luck with your pruning.  There are so many varieties of perennials that I have only named the ones popular in my garden zone.  Do not hesitate to ask if I have missed something you have in your garden.

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6 thoughts on “The when and how of pruning perennials

  1. Hi Lori, I appreciate your gardening tips. I pruned my salvia and peony quickly this morning. I never know when to do these things. I will do the day lilys tomorrow. Happy Thanksgiving

    Sylvia

    >

    Liked by 2 people

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