If I were given the choice between venturing out into my yard in winter with my pruners or setting aside some time to tackle the task in late summer to fall, the latter would win by a landslide.
Not only is it more favorable to avoid the cold, but, for some plants, it’s better for their health to prune in late summer or autumn rather than in winter. Certain shrubs and trees don’t require pruning during winter, and doing so will actually leave your plants more vulnerable to the cold instead of stimulating growth.
Here’s what you need to know about which plants will benefit most from a thoughtful snip in September. It’s important to do your research and make a pruning calendar, because, though many plants will thrive after a prune, there are also many plants you should never prune in fall that should be left until spring.
1. Lavender
Late summer or early fall is the best time to prune lavender to encourage new growth and maintain a uniform shape. In the summer, pruned parts of lavender bushes will be vulnerable to harsh sun, and come winter, you don’t want to tamper with your lavender too much and expose fresh cuts to chilly temperatures. So September is ideal to cut them back, with a follow-up prune in spring if necessary.
‘Lavender, especially varieties like Munstead and Hidcote, should be pruned in September to keep them compact and encourage better blooming next year,’ says Michael Clarke, a landscape architect, horticulturalist, and founder of Yardwork. ‘This prevents them from becoming woody and sprawling, which is necessary as woody lavender stems can crack or split over winter, decreasing flower production.’
To prune lavender, trim back any browning spent stems on a dry day, ensuring you do your best not to cut away any fresh green sprigs of growth. Pruning lavender after it has rained can increase the chance of fresh cuts developing plant fungus, so it’s vital to keep your lavender dry.
When I prune lavender at the end of summer, I use bags like the HRX Package white organza pouches from Amazon to collect any fresh buds. I keep them in my home to spread their lovely fragrance, and place one in my pillowcase to promote better sleep.
2. Wisteria
Now is the time to prune wisteria thoroughly before fall kicks in. This plant thrives best if it receives a prune twice per year: once while it’s still dormant in late winter before its spring bloom, then again in late summer after it’s finished flowering.
'Prolific, Macrobotrys, and Alba are the top varieties of wisteria I’d recommend pruning in the first half of September if you missed August pruning,’ says Michael. ‘Cutting back any spent or overly wispy growth now will help ensure your plant doesn’t become tangled and overgrown, and that flowering continues without being hidden by an excess of foliage.’
Cut back long summer shoots using your pruning shears, and focus on shaping your wisteria in a way that looks neat and allows you to see your blooms. If you’re struggling to reach high-up areas, I recommend investing in a set like the 3-Piece Fiskars Set from Walmart, which includes pruners as well as loppers with longer arms.
3. Roses
While early spring is the traditional time for pruning roses, many varieties can benefit from a good trim in September before cooler weather begins to settle in. This will help to prevent your rose bushes from looking leggy and protect them from wind damage in the fall.
Michael says: ‘Many varieties, such as Gertrude Jekyll, Bonica, and Iceberg, do well when trimmed in September. If left unpruned, they can develop tall growth that may get damaged or uprooted by winter winds.’
In addition, if you are pruning rambling roses, this must be done after flowering in summer or early fall, as unlike other rose types, they bloom on old wood.
To encourage healthy overwintering, prune rose bushes using a pair of shears like the ever-popular Fiskars ⅝” Bypass Pruner from Amazon. Remove any dead or damaged flowers, as well as branches that are getting too long or beginning to cross over one another too much. These branches can get tangled and cause parts of your rose bush to snap.
4. Summer-Fruiting Raspberries
Wild berries are truly a blessing to live around, especially if you love baking and making jams like I do. September is the perfect time to prune back your summer fruiting raspberries to encourage optimal growth and an abundant harvest of juicy gems next year.
‘Summer fruiting raspberries that have finished producing berries can be pruned back by removing canes to allow next year’s growth to take over,’ says Michael. ‘Old canes will become diseased and unproductive if left unpruned, and crowded canes can reduce airflow, increasing disease risk.’
When pruning raspberry plants, cut away any brown woody canes that have finished fruiting down to ground level. Then, if you have healthy sprigs that require assistance standing up, tie them back to a plant support, like the Royal Imports Green Wood Plant Stakes from Amazon, to encourage sturdy growth and continued climbing.
5. Blackberries
September is also the ideal time to prune blackberry bushes. In the same way as raspberry plants, spent blackberry canes can begin to die, and if left attached to the rest of the plant, diseases can settle in.
Reese L. Robbins, founder of Just Pure Gardening, says: ‘Those canes that fruited this summer? They’re done. Cut them out to reduce disease and make room for new growth.’
If you aren’t a fan of traditional canes and wish to try something else for your climbing plants, this 3 Feet Natural U-Hoops Bamboo Trellis from Amazon could do the trick. You may need to provide temporary support to the shoots in the centre while they grow tall enough to reach the top, but it has the potential to look stunning.
6. Perennial Herbs
Perennial herbs such as sage, thyme, and oregano will begin their journey to dormancy after the summer comes to a close, so September is a great time to give them a prune before they fall asleep.
‘A light September prune keeps these herbs healthy and compact as they head into dormancy,’ says Reese. ‘Unpruned herbs can get woody, leading to weaker spring growth, so a light trim can make a big difference.’
Trim back about one-third of each plant, targeting your attention on areas that look like they’re browning or losing freshness. It may seem like a lot, but these plants are quick to rejuvenate come spring.
7. Climbing Hydrangeas
Climbing hydrangeas will greatly appreciate a September snip to remove their spent flowers and encourage bountiful spring blooms. This month of the year is ideal for pruning hydrangeas as they will have finished their summer flowering.
‘Skipping pruning can lead to a messy shape, as well as the development of diseases and smaller future blooms,’ says Reese. ‘Remove any dead flower heads you see and lightly shape the plant using your pruning shears to create a nice, uniform look.’
If I notice any flowerheads are starting to turn worse for wear on my plants, I try to collect the petals in a nice jar like this Vintage Glass Jar with Wooden Lid from Amazon before they die. Over time, the jar will fill up with a DIY potpourri straight from your yard.
