August is an excellent month for pruning many shrubs and trees in the landscape, just ahead of the fall growth spurt. It's also a perfect time for pruning backyard fruit trees for size control. Removing excess growth now instead of waiting until January will help keep fruit trees smaller.
Don't Prune in Late Summer and Fall
Pruning shrubs in August or early September may encourage a late flush of growth. This new growth may not harden sufficiently before the arrival of cold weather and be susceptible to winter injury.
Perennials to prune in early summer: joe-pye weed (Eutrochium), tall coneflower (Rudbeckia 'Herbstonne'), bee balm (Monarda), catmint (Nepeta), yarrow (Achillea), balloon flower (Platycodon), Culver's root (Veronicastrum), Veronica and garden phlox (Phlox paniculata).
Pruning services often recommend pruning roses in the late summer, since rosebushes can usually produce one more round of flowers before temperatures drop in late October. Remove dead canes, crossing canes and suckers. For canes that you want to blossom this fall, cut back to groups of five leaves.
By not cutting back the statuesque achilleas, eryngiums, perennial astilbes, sedums, alliums and many ornamental grasses, you can enjoy their structure against a winter sky. The sight of their stems silvered with frost adds a whole new level of interest to the garden.
It's important to cut back foliage in the fall to protect flowering plants from disease and give them a clean start for regrowth as winter starts to turn into spring. However, there are some plants you can keep around through the winter since they benefit wildlife and still offer visual interest for your home.
To prevent the disease from returning the following year, we suggest cutting the plants back in the fall and removing any debris – no matter the variety! It will give your plants a clean start next season. *Destroy any foliage with symptoms of powdery mildew and disinfect pruners before trimming other plants.
Never shear a shrub in fall (or ever, actually, but that's another article) and leave major pruning or renovation for late winter/early spring, or immediately after bloom for spring-flowering shrubs.
DON'T prune during fall.
No matter what type of shrub you have, fall pruning can stimulate late-season growth that may not have enough time to harden. This can weaken and damage the plant—especially if there's an early frost. Instead, wait until winter and trim bushes when the plant is in deep dormancy.
Summer is an excellent time for restorative pruning. You can correct problems that have resulted from over-pruning or poor pruning. You can also clean up damage from winter and spring storms. Proper pruning will begin to restore most plants' natural shape.
Similarly, avoid trimming summer flowering shrubs before they have flowered and wait to do so until after they have finished flowering. Non-flowering shrubs can be trimmed at any point in the summer to shape them or to reduce their size, but remember that regrowth will be slow during hot, dry, and stressful conditions.
I love messy perennial garden beds, as long as every plant gets its chance to shine. If you're also wondering whether you can prune plants in the summer, the answer is yes. But if you're thinking “Isn't summer the season I'm supposed to relax and just let the garden be?” then the answer is also yes.
Best Time to Prune Evergreen Shrubs
Pruning evergreen bushes is best done in late March or early April before new growth begins. Light pruning can also happen in late June or early July. Avoid pruning evergreen shrubs in the fall, since they are more susceptible to winter injury.
Boxwood shrubs pruned between late summer and fall will leave them susceptible to frost damage, especially if there's an early frost. Wait to prune your boxwood until after April 15, the average last spring frost date for St.
The period between the full and new moon (third and fourth quarters) is best for harvesting, slowing growth, etc.
Late summer or early fall pruning causes vigorous re-growth of tissue, which in some cases may not harden off by the time winter arrives, leading to possible cold damage to the new growth.
Summer-Blooming Trees and Shrubs
Prune them in winter while they're dormant, or in early spring just before they push out their new growth. You can even cut them all the way to the ground in late winter, and they'll still bloom that same summer.
Common Mistakes
Prune just above a healthy bud, with the bud pointing in the direction you want the plant to grow. Cut at a 45-degree angle, with the low point of the cut opposite the bud. Don't cut too far from or too close to the bud you want to encourage. Leave a “collar” when cutting off a branch.
Don't shear the branches of spring flowering shrubs (Forsythia, Lilac, New Mexico Privet, Spirea, Flowering Quince, and others). These shrubs produce flowers on last year's wood, so removing old growth will reduce or prevent flowering. These plants should be pruned immediately after they are done blooming.
You probably already know just how fast shrubs grow and start to look messy. If you wait too long, your shrubs will start to become an eyesore. Pruning less of the plant but more frequently is by far the best for the overall health of it. We recommend every other month, which comes out to be five times per year.
When to Cut Back Hostas. As a general rule, hostas should be cut back in the late fall. Start with leaves that have wilted or turned brown. Healthy leaves can stay a bit longer to help the roots store needed energy.
It's during the early fall (September and early October in my Pennsylvania garden) when the night-time temperatures start to drop, that the carbohydrates begin to make their way back down to the plant crown. Wait to prune back hostas until the leaves turn completely yellow or fully brown.
However, there are cultivated plants which are more susceptible to problems if the old foliage and dying stems are left to rot. Diseases can overwinter in dead foliage, as can slugs and other pests. Old stems can also get battered about by fall and winter winds, which will damage the plant's crown and roots.