8 Reliable Perennials To Divide In August For Long-Term Garden Health

While dividing is a very useful and productive technique in the garden, many new gardeners just don’t understand its purpose and aren’t able to take full advantage of it. 

In today’s article, not only will we discuss the importance of division in the garden, but also look through a list of reliable perennials that should be divided in August for long-term results.

This guide will work especially well for gardeners in Zones 5-9, where the August soil would still be warm enough for root recovery. In case you’re in a cooler zone, consider dividing your perennials in early spring instead.

First Of All, Some Signs Your Perennials Need Dividing

In most cases, your perennials will communicate with you when they need dividing. Of course, it won’t be a straightforward verbal conversation, but there will be signs you must look out for. These signs include: 

A Quick Guide On How To Divide These Perennials 

Optimal division always starts the day before.

While you’re dividing, it’s also a great time to tidy up nearby plants. Here’s a list of perennials you can safely cut back in August.

Perennials You Can (& Probably Should) Divide In August

1: Daylily (Hemerocallis)

Daylilies are hardy perennials with tough roots that will have to be separated using a spade or some sort of small saw. Give them plenty of sun throughout the day and divide them every 3-5 years for slowly but surely improving blooms. 

August is also the perfect time to divide them, since they’ve usually finished blooming by the end of the month and still have enough warm soil to recover before fall.

And if you’re growing a repeat-blooming variety, this guide can help you keep them flowering late into the season.

2: Bearded Iris (Iris Germanica)

Many experienced gardeners consider hollowness in the center of bearded irises a sign that division is needed.

You want to cut bearded iris rhizomes and replant the younger outer sections. After dividing, cut the leaves down to about 4–6 inches to help the rhizome recover and avoid excess moisture loss.

Unfortunately, this one is the kind of perennial that needs lots of sun and proper drainage 

3: Black-Eyed Susan (Rudbeckia)

Black-eyed Susans have a tendency to become overcrowded in tight areas, which sometimes results in floppy, weak growth overall. It’s best to divide them into chunks with strong and capable roots, ideally in ideally in well-draining soil that doesn’t stay soggy, but also isn’t bone-dry.

4: Coreopsis

If not divided properly every few years, coreopsis can spread fairly quick while having fewer blooms. I’d suggest you use some sort of sharp spade or garden fork to slice the clumps apart for division. This perennial can also tolerate hot conditions well and actually prefers to be planted in the heat. 

5: Shasta Daisy (Leucanthemum)

Shasta daisies are super quick and easy to divide. And, just like Bearded Iris, they can become leggy or hollow-centered if you don’t divide them.

Ideally, you should be dividing them every 2-3 years to keep the base soil safe and nutrient-dense. To no surprise, Shasta daisies love the heat and thrive in full sun. 

6: Yarrow (Achillea)

Dividing can help prevent that dreadful woody center in yarrow plants and give them the opportunity to spread more evenly through the garden (otherwise, it can become invasive). Because of their drought-tolerant nature, yarrows naturally need very little maintenance apart from some water, fertilization, and timely division. 

7: Garden Phlox (Phlox Paniculata)

Because garden phlox are super sensitive to mildew-related issues, dividing them from time to time ensures mildew problems won’t surface, and the air circulation around the perennial always promotes fresh, high-quality growth.

If you’re just getting started, here’s a broader list of easy-to-divide perennials that multiply fast and bring more blooms every year.

8: Sedum (Hylotelephium ‘Autumn Joy’)

The sedum is another reliable perennial that can benefit from a little dividing action. Clumps might slowly begin to flop or die out, that’s your cue to start considering division.

Separate the clumps using your hands and just give them full sun and occasional watering to achieve the best low-maintenance sedum growth. You can divide it now, just after flowering, or early spring.

Let’s Conclude

Not all plants enjoy being divided, though, this list covers the ones you should leave alone.

Plant division is a challenging subject to address, as many things can go wrong during the process, even when the rewards are clear and worthwhile. 

When you decide to divide your perennials, do it with intention and heart. In most cases, division isn’t “necessary”, but if you do it with knowledge, gentleness, and intention, flowering results, and your overall garden health can be significantly improved!