10 Perennials to Prune During Summer for an Even Better Showing Next Year

Catmint

Catmint (Nepeta) offers pretty upright blooms in an elegant lavender color. Like other members of the mint family, catmint is super easy to grow and spreads rapidly, so plant with caution.

As far as summer perennials go, catmint is at the top of horticulturist Christine Froehlich’s list for pruning. "The number one to prune back is nepeta. Once it flowers and starts looking sloppy, cut it back to the center. In about two weeks, you’ll have a fresh-looking plant that will re-flower,” she says.

• Zones: 3 to 8
• Size: 24 inches tall x 24 inches wide
• Care requirements: Full to partial sun; well-drained soil

Lilac

Given the chance, wonderfully fragrant and delightful lilac (Syringa) will start to grow too tall and too wide. Luckily, you can control this by cutting the plant back. “I like to prune lilacs right after flowering. Remove most of the basal growth and cut top growth back to size if overgrown,” says Froehlich. You can also remove any damaged wood. If your lilacs get too tall, consider cutting back the tallest limbs.

• Zones: 3 to 7
• Size: 8 to 16 feet tall x 6 to 12 feet wide
• Care requirements: Full sun to partial shade; moist, well-draining soil

Iris

When it comes to iris, there are so many choices of colors and types which can dictate the trimming you do throughout the summer. “Siberian iris get pretty floppy as summer wears on,” says Froehlich. “Cut them in half or prune judiciously away from other plants.” She recommends cutting German iris in half, forming a fan shape. Also, go ahead and prune away any dead foliage.

• Zones: 3 to 9
• Size: 12 to 36 inches tall x 24 inches wide
• Care requirements: Full sun; well-drained soil

Phlox

Phlox is one of those gorgeous plants in which many tiny blossoms grow in tandem to create the effect of a single giant bloom. “Phlox should be cut in half no later than the first week in June,” says Froehlich. Be sure to deadhead, too.

• Zones: 3 to 8
• Size: 24 to 48 inches tall x 24 to 36 inches wide
• Care requirements: Full to partial sun; moist soil

Hydrangea

Some hydrangeas need to be cut back during summer, but it depends on the variety you're growing. “Pruning hydrangeas is totally dependent on what kind you have,” says Lorraine Ballato, a garden and hydrangea expert. Depending on the variety, you may have blossom buds that form on new growth from the current season or on older woody growth from the year before. It’s critical to know the difference so that you don’t accidentally wipe out a year’s worth of blossoms. 

• Zones: 3 to 9
• Mature size: 2 to 6 feet tall x 3 to 12 feet wide
• Care requirements: Partial sun; well-drained, damp soil

Daisy

Daisies (Bellis perennis) have strong stems with attractive foliage, but they’re not super substantial or woody, so you’re not “pruning” here to achieve shape. “Daisies should be deadheaded as soon as those flowers fade to keep the garden neat and tidy,” says Ballato, noting that not all daisies will put on more flowers after pruning. “There are some varieties that are rebloomers. That's where it really counts.”

• Zones: depends greatly on variety; 3 to 9
• Mature size: 18 to 36 inches tall x 12 to 24 inches wide
• Care requirements: Full sun, well-drained, fertile soil.

Sedum

Sedum is a splendid landscaping plant—it has an interesting shape that provides texture and drama to the garden throughout the year. Pruning early can help shape and adjust the height of the plant. “You can cut back sedum in early summer to keep the plant lower if it is a tall one,” says Ballato. “But this depends on the variety of sedum you have. They are usually later season bloomers, so cutting them too late can possibly prevent that flowering cycle.”

• Zones: 3 to 9
• Size: 24 inches tall x 24 inches wide 
• Care requirements: Full sun to partial sun (depends on variety); well-drained soil

Daylily

As with sedum, daylilies (Hemerocallis) provide the garden with visual interest even when they aren’t blooming. The thick, wide leaves flourish in sun or shade, and the bell-shaped blossoms are well worth the wait. The flowers may not last long—they live up to their name, so to speak—but you may be able to coax additional blooms throughout the year with pruning. “Deadhead daylilies to neaten up the plant and encourage rebloom on those varieties that have that genetic capability,” says Ballato.

• Zones: 3 to 9
• Size: 24 to 48 inches tall x 24 to 36 inches wide
• Care requirements: Full to partial sun, well-drained soil

Azalea

When you prune your azaleas (Rhododendron) depends on the type you're growing. “Azalea is a shrub that flowers in spring to early summer,” says Ballato. Generally, the best time to cut back this plant is right after it flowers. If you wait too long, you will cut off next year's buds. Also, some varieties are fall rebloomers so summer cutting isn't an option, says Ballato.  

• Zones: 5 to 9
• Size: 24 to 48 inches tall x 24 to 48 inches wide
• Care requirements: Partial shade; damp well-drained soil, slightly acidic

Beebalm

Beebalm (Monarda) grows tall and flowers brilliantly during the year, then the stalks fade away and die off during winter. Once spring arrives, bee balm regrows from the base of the soil. You can let the plant go without any pruning, but pinching off a few early leaf stems when the plant is about 1-foot-tall will encourage it to become more bush-like. You can also gradually deadhead the blossoms as they fade to help promote new flowers.

• Zones: 3 to 9
• Size: 36 inches tall x 8 inches wide
• Care requirements: Full sun; well-drained soil