10 Plants To Avoid Pruning In September And What To Do Instead

You may be tempted to prune back your garden at the first sign of fall, but when it comes to certain plants, you might want to put away the shears. If you want a tidy winter landscape that's ready for new growth come springtime, pruning these plants in September can do more harm than good. Pruning encourages new growth, increases flowering, and decreases the risk of disease when done at the right time. However, knowing when to prune your plants and when to leave them alone is necessary for your plants' success.

Many plants can be pruned in late summer to early fall, but for some, September is too late in the season. Certain flowering plants, like Chinese fringe flowers, bloom on old wood growth from the previous year. Others, like some hydrangea varieties, bloom on new wood growth from the current season. Pruning either of these plants at the wrong time will remove flower buds and prevent them from blooming in the season. For others, such as Russian sage and rosemary, you should avoid pruning these plants in the winter or close to it, as it will leave the new growth susceptible to damage from harsh cold and frost.

Chinese fringe flower (Loropetalum chinense) blooms twice, once on old wood and once on new wood, so pruning is tricky. Pruning it in September will reduce the number of blooms you'll get in the winter and spring. Instead, you should prune this shrub in late spring, after it has finished its first flowering period.

Forsythias are loved for their bright yellow flowers, which are among the first trees to bloom in the spring. Though beautiful, this plant can easily become overgrown. They produce flower buds on the current season's growth, so you should wait until the shrubs have finished flowering to prune. Don't wait until September, however — this will not give the plants enough time to produce flower buds and new growth before fall.

Azaleas and rhododendrons, both in the same genus and often mistaken for one another, require a lot of the same care. These plants flower on old growth, and pruning as late in the season as September will remove the recently-produced buds that will flower in the spring. Removing dead, damaged, or diseased branches can be done at any time to preserve the health of the plant. However, heavier pruning, like shaping or rejuvenation pruning, should be done just after they're finished blooming.

Taking small cuttings of rosemary (Salvia rosmarinus) for cooking in September won't hurt the plant. However, you should avoid pruning at this time. While regular pruning can encourage denser growth, it should be done right after the plant has finished blooming in late spring to early summer. Pruning too late encourages new growth that may be too weak for harsh winter conditions.

Pruning is essential for the common lilac (Syringa vulgaris). If this large, woody shrub grows unchecked, its broad upper branches will prevent its lower foliage from receiving sunlight. Occasional pruning also encourages healthier growth. However, September is not ideal, since autumn is when lilacs form flower buds for next spring's blooms. The best time to prune lilacs is right after flowering in late spring, typically early June. This gives the plant time to grow new flowering wood before winter.

By September, you still have a few months to go before you can prune American beautyberry (Callicarpa americana). The American beautyberry fruits from September to December. If you prune now, you'll miss out on a winter garden full of berries. These bushes don't necessarily need pruning, but you can do so to keep them neat and compact as well as help your fruit grow and produce faster. The best time to prune these plants is in late winter or very early spring.

From mid-summer to early fall, Russian sage (Salvia yangii) bursts with beautiful purple flowers you won't want to cut away. Pruning now can also leave new growth vulnerable to winter damage. You should prune Russian sage once a year after the last frost of the season, usually in early spring. You can also wait until later in the spring, when it will be easier to identify dead branches.

Hydrangeas don't need regular pruning, but gardeners often do so to remove dead foliage, manage size, rejuvenate old plants, and reduce disease severity. However, doing so in September is discouraged for some varieties. Hydrangeas that bloom on new wood, like panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens), should be pruned in late winter to early spring, before flower buds emerge later in the spring or summer.

When it comes to prune mock orange (Philadelphus), it's best to prune during dormancy in late winter to early fall rather than in September. Alternatively, you can prune in the summer just after flowering. Pruning at either of these times gives mock orange plenty of time to recover before winter or the next blooming season. Mock orange blooms on old wood, so pruning it in September will hurt its ability to produce flowers and their sweet citrusy scent.

Pruning camellia (Camellia japonica), a woody shrub, should be limited to dead or damaged branches and shoots that are way too long. Hard pruning is not usually recommended, though it can revive a dying camellia plant when done in early spring. Otherwise, camellias bloom on old growth, so prune them immediately after flowering to allow flower buds to grow in time for the dormant season. This usually occurs in the early summer, making pruning in September a bad idea.