Which plants you should prune back in the fall

 

For some reason, the fall season is when many gardeners get the itch to prune back plants in their gardens.  The guidelines are as follows, at least for our zone 4 to 5 gardens here in Ottawa, Ontario:

  • if a shrub blooms early (before June) wait until after flowering to prune.  Some examples of early bloomers that need that old wood to bloom on are lilacs, forsythia, bridal wreath spireas, sand cherries, weigela, ninebarks, rhododendrons, viburnum, cranberry bushes, flowering dogwoods and magnolias.
  • if the shrub blooms after June, it can be pruned back in the fall or in the early spring when new growth is visible.  Examples include Snowball and PeeGee Hydrangeas, spireas (except for bridal wreath), Butterfly bush, smoke tree, hibiscus (rose of Sharon), and red stemmed dogwoods.
  • woody shrubs like boxwoods, junipers and cedars can be trimmed back in the fall too, but also throughout the growing season (spring and summer)
  • some shrubs are best pruned while dormant (late fall to very early spring, late February to early March)  These include barberries, smoke bush, crepe myrtles, spireas (except bridal wreath variety), dogwoods, and cotoneasters.
  • to rejuvenate shrubs that flower poorly, are overgrown or straggly, cut them back to just above the first bud above the soil while the plant is still dormant.  Shrubs that do well with this drastic treatment include spireas, lilacs, ninebarks, forsythias, barberry, weigela, blue mist, forsythia, honeysuckle, and potentilla (cinquefoil).  You may sacrifice the flowers the first season after this rejuvenation, but the plant will be healthier.
  • deciduous (non-evergreen) trees are best pruned when dormant (late winter) as well.  It is much easier to see the structure of the tree before the leaves come out.  Winter pruning also prevents the formation of bacteria and disease in the cuts. The wounds will heal quickly as new growth starts shortly after pruning.
  • dead branches can be cut off any time in the season.
  • after the first frost, remove any leaves from roses and apply mulch to the crowns. This prevents the plants from heaving from the ground during freeze/thaw cycles. You can cut the longs stems of the most tender floribundas, hyrdrid teas and grandifloras back to 20 inches before winter too to prevent them from breaking off under a heavy snowfall.  Another tip for tender roses is to apply a collar around the bush and fill it (loosely) with leaves.  Wait to prune others back until daffodils start to bloom in the spring to ensure the ground temperature is sufficiently warm.  Dead or broken branches can be cut off in the fall or any other time of the season.  Suckers can also be removed in the fall, cutting them out as close to the base of the plant as possible.

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Perennials can be, but do not have to be, deadheaded (remove dead blossoms) and cut back in the fall.  Remove sturdy flower stalks (coneflowers etc) right back to the foliage at the base of the plant.  Some gardeners like to leave these stalks on the plants over the winter for birds and their snow-covered beauty.  On softer plants simply remove the browned and dead looking, limp or soggy foliage (daylilies, peonies, bleeding hearts etc) and cut back their stems to six or eight inches from the ground.  I like to do everything I can in the fall because spring seems to be so short lived these days and I run out of springtime hours in the gardens.  Whenever you clean up your gardens, remember to harvest the seeds for future (freebie) plants as I did for my cottage garden.

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pictures from Pexels and Pixabay

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October blooms

I love this fall (summer like) weather we are having here in Ottawa.  Many of the perennials in my own and my clients’ zone 4 to 5 gardens are still in bloom even though the calendar says October…

 

 

I cannot ever remember a clematis reblooming in October as this beautiful pale purple one has…

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If this is fall, I’ll take it, weird or not

Normally fall or autumn is my least favourite season as all the plants in my gardens start to die off in preparation for the winter ahead.  The calendar says September 21st  was the first day of fall or autumn, but Mother Nature is displaying something quite different this year. We have had the most beautiful summer-like weather lately here in Ottawa, more summer-like than June, July, and August.

The gardens I work in are all confused.  Many perennials have rebloomed (roses, clematis, and weigelia)…

 

and others that usually look unsightly around this time of year (peonies and bleeding hearts) are still green and lush.   Coneflowers have been in bloom all summer and continue to look great.  The monarch butterflies are loving the lasting blossoms…

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Is September the new July?  If this is fall, I’ll take it, weird or not!

 

 

 

 

The reason you should not prune some shrubs in the fall

In a recent post I listed many shrubs categorized by when you should prune them.  The reason you should not prune many shrubs in the fall is because you will remove most of the buds that will turn into flowers the following spring.  Examples of these buds are shown here in magnolia, rhododendron and forsythia shrubs…

 

If you must prune these shrubs to control their size, wait until after they bloom in the spring to do so…

please be sure to visit my slightly more humorous blog YOUR DAILY CHUCKLE  It is guaranteed to make you LOL.

Why do leaves change colour in the fall?

Have you ever wondered why leaves change colour in the fall?  This chemistry lesson will teach you all about photosynthesis and chlorophyll.  In the spring of the year new leaves emerge on the trees and plants as a bright green colour….

This bright green colour is due to the large amount of chlorophyll present in the leaves.  Chlorophyll is produced through  photosynthesis which needs water, sunlight and carbon dioxide to happen.  In the spring all of these requirements are available; the melted snow and rain provide the water and the sun is at an advantageous angle in the sky.

In the fall or autumn however, the sun is at a much lower angle with fewer daylight hours.  The soil  around the base of the trees contains much less moisture in the fall than the spring. Without adequate sunlight and water, photosynthesis shuts down, no chlorophyll is produced, and the leaves on the trees turn red, yellow, orange and brown…

That is your chemistry lesson on why the leaves change colours!  These colours on the trees are very pretty to look at, especially here in Canada and the northern USA where the roadsides are cloaked in them.  Get out and enjoy the colours of fall today!

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.

Pruning Shrubs

                                                                            

The rule of thumb for pruning or cutting back shrubs is this:  if it flowers before June, cut it back immediately after flowering.  If it flowers after June, cut it back first thing in the spring.  The reason for this rule is because spring blooming (before June) shrubs form flowers on the previous years’ growth, so if you cut it in the spring you will be cutting off the stems that will be producing flowers that season.  Shrubs grown primarily for their foliage (dogwood, burning bush, dappled willows etc) should be pruned in the early spring, before new growth starts.

Spring pruning  (just as growth starts)

  • late blooming (pink) spireas
  • peegee hydrangeas
  • burning bush
  • late blooming clematis
  • holly, very early, while still dormant
  • rose of sharon
  • late blooming heathers
  • cotoneaster (minimal)
  • yew, before new growth starts, then several times during season
  • weigelia
  • late blooming lilacs
  • shrub roses
 
         
             
After flowering:
  • early blooming clematis
  • rose of sharon
  • sand cherry
  • mock orange
  • rhododendrons
  • magnolias
  • early heathers
  • barberry
  • early blooming (bridal wreath) spirea
  • forsythia
  • most lilacs
 
Pruning in the fall can cause new growth that is stimulated by the pruning to be damaged by cold weather. Fall pruning will also remove late forming buds that will produce flowers the following spring.  For these reasons, pruning is best done in spring or summer.   Dead, diseased or crossing branches however, can and should be pruned as soon as they are discovered.