October is an ideal time to divide these 7 popular perennials – here's how to reinvigorate plants for better blooms and get new ones for free

If you want to expand the collection of your best-performing perennials, fall is a great time to do it. Dividing perennials is a quick and easy way to get multiple new plants from one clump, and for free. And there is a fantastic choice for perennials to divide in October – great news if you have any of the following in your yard.

The flowering of older, congested clumps of perennials declines over time. Dividing plants every few years rejuvenates them, and the reward is better displays. As splitting and transplanting perennials can stress them, the warm, moist soil in the fall is ideal for them to settle and put down roots before the cold winter weather arrives.

If you want to add dividing plants to your fall gardening checklist, we reveal some of the best perennials you can choose in October. These spring and summer-flowering plants are ideal for the task this month, and we take a close look at how to divide plants so you have new clumps to add to your garden and stunning flowering displays for years to come.

Perennials to divide in October

Knowing when to divide plants makes sure you don't risk the health of your perennials by doing so at the wrong time of year. The best times for division are fall and spring, and you don't want to do the task during the coldest or warmest seasons. As mentioned, the soil is warm and moist in the fall. However, if you have particularly cold or wet falls, or you want to split more tender plants, it is advisable to wait until spring.

1. Hostas

You can divide hostas in the spring or fall, but the moist soils and regular rains of fall often mean that newly-divided clumps will need little watering. It is recommended that you divide hostas every four to five years. Whether in the ground or hostas in pots, the method remains the same.

Carefully dig up the clumps and remove as much soil as possible. You can divide the clumps by cutting downwards through the crown with a sharp knife or garden knife, or by separating smaller sections by hand. Your choice of tool will likely depend on the size of the clump.

Any new section needs to have at least one eye and roots, but the larger the section, the more likely it will be successful and grow quickly. Remove any damaged sections and dead leaves, then replant the new clumps quickly at their original depth and water deeply.

2. Daylilies

Daylilies, also known as Hemerocallis, grow in tightly-packed clumps and are best divided every three to five years. This ensures a great display of vibrant blooms, while not dividing daylilies will mean diminishing displays year after year as the clump fights amongst itself for water and nutrients in the soil.

Gently lever the clump out of the soil, and remove as much soil as possible so you can get a good look at the fibrous root system. Use a sharp spade, gardening knife, or two forks back-to-back to separate the clump into smaller divisions, each of which needs three fans (or stems) and a good set of roots.

Store the divided sections in a bucket of water until ready to plant. When you do put them in the ground, which is best done quickly, plant the daylilies so the crown is an inch or two under the surface. Cut back the daylily foliage to around six inches in height, and keep the new transplants well-watered.

3. Crocosmia

The fiery displays of crocosmia can ignite a summer bed, but overly congested clumps will disappoint. If your crocosmia is not blooming to its former glory, it may be that it needs to be divided. Not only will you have new clumps for free, but your favorite crocosmia varieties will be back to their best.

To keep the plants performing well, you should divide crocosmia at least every three years. In the fall, after flowering, is an ideal time to do this.

Gently dig up the clump and shake off as much soil as possible. You can pull apart crocosmia corms by hand, without the need for a sharp spade or knife, as with other perennials.

Separate and replant the top two corns attached to the stem, which are the most vigorous. Plant them two or three inches deep, with the pointed end upwards, in a sunny spot. Crocosmia can grow in shade, but plants perform best in full sun.

4. Peonies

Peonies have a short yet spectacular flowering season. While they don't require regular splitting, like many other perennials, dividing can be a way of propagating peonies if you want more of any particular variety, or if a plant has gotten too large for its space.

Fall is the best time to divide and transplant peonies, provided they can get four weeks of growing in their new home before you get any hard frosts. Peonies divided in the fall are capable of flowering in spring, but it will be a small-scale show, and it can take a few years to get to full strength.

Cut back the peony foliage in fall, before carefully digging up the clump and removing the soil from around the roots. Using a sharp spade or knife, cut the peony into sections, ensuring each one has at least three healthy eyes. To be safe, aim for each to have 5-8 eyes.

Plant the sections quickly with the eyes no more than an inch deep in the soil. Planting peonies too deeply is usually the cause of a plant not flowering.

5. Astilbe

Astilbe is a great full or part-shade perennial, able to bring some height, drama, and pops of color to darker spaces in the garden. The plants prefer shade and can scorch when growing in too much sun.

When you grow astilbe, they are low-maintenance but do benefit from being divided every three or four years. The clump can get large and overcrowded, which affects blooming and also leaves the plant more susceptible to powdery mildew.

Divide the plant after it has finished flowering. Start by giving it a good watering, unless it has rained in the day or two prior, and then dig around the plant to lift it from the soil. Shake off the excess soil and separate it into new sections, either by hand or with a spade or knife, aiming to get between three and five sections from one clump.

6. Black-eyed Susan

Black-eyed Susans, also known as rudbeckias, are reliable flowers and produce bright swaths of yellow, orange, or bronze blooms that attract birds, hummingbirds, and butterflies.

An issue that comes with their profuseness is that they are also prolific self-seeding flowers. As a result, things can get very crowded, and the flower bed can become a battleground for soil and nutrients.

Digging up and separating sections in the fall after flowering gives plants room to breathe, plus you get more clumps to plant in other areas of the garden.

Firstly, cut back the Black-eyed Susan in the fall. Then lift the clump carefully, remove the soil, and cut it into sections with your sharp spade or knife. Plant the new clumps as soon as possible in a sunny spot, ideally one that receives at least six hours of sunlight a day.

7. Hardy Geranium

When you grow and care for hardy geraniums, they are prolific plants that spread quickly.

This fast-spreading nature can leave them overcrowded. Often, the center of the clump is left looking bare compared to the edges, which remain covered in flowers. This scenario isn't ideal for any hardy geranium varieties, so you can avoid this happening by dividing the plants every 3-5 years to control their size, keep your geraniums blooming at their best, and get new plants to add to your garden.

After flowering and before the first hard frosts is the ideal time to divide hardy geraniums; otherwise, it is a job to add to your spring gardening checklist. Dig up the clump and separate it into pieces with a sharp tool.

You can get several divisions from one large clump, and each must have healthy shoots and roots to be successful. Each of these sections is best replanted straight away, planted with the crown sitting at soil level.

A good watering is essential, and a feed with a handful of bone meal will help promote strong root development. You can get organic bone meal at Burpee to use when replanting divided perennials.

Shop the tools professional gardeners use to divide perennials

Not all plants are suitable for dividing, so take care and do some research before choosing perennials to divide in October. Check this guide to plants you should never divide, which features some popular perennials you risk losing altogether if you attempt to lift, divide, and transplant them.