When the weather cools and the garden begins to wind down, fall offers a unique opportunity to refresh your perennial garden by dividing and transplanting plants. While many gardeners focus on planting new perennials in the spring, fall is the perfect time to divide some of your existing perennials to rejuvenate them, control their size, or simply propagate new plants. But not all perennials should be divided in the fall. Understanding which ones will thrive when divided at this time of year is crucial to maintaining a healthy garden.
Why Divide Perennials in the Fall?
Dividing perennials is an essential part of garden maintenance, ensuring that your plants remain healthy and productive. Over time, perennials can become overcrowded, leading to diminished blooms, smaller leaves, and a general decline in health. Dividing them allows for better air circulation, encourages more vigorous growth, and gives you more plants to fill in empty spaces in your garden.
Fall is an excellent time for dividing many perennial plants for several reasons:
- Cooler temperatures: The cooler weather reduces stress on newly divided plants, allowing their roots to establish before winter.
- Moisture: Fall often brings more consistent rainfall, which helps newly divided plants re-establish their roots more easily.
- Dormancy preparation: Dividing in the fall gives plants time to rest and recuperate through the winter months, encouraging stronger growth come spring.
However, not all perennials are suited for fall division. Let’s take a closer look at which ones you should divide in the fall and why.
Best Perennials to Divide in the Fall
1. Daylilies (Hemerocallis)
Daylilies are incredibly easy to divide, making them a favorite for many gardeners. Over time, daylilies form large, dense clumps, which can reduce blooming and result in a less-than-ideal appearance. Dividing them in the fall helps restore their vigor and ensures a fresh burst of flowers the following year.
How to Divide Daylilies in Fall:
- Step 1: Wait until after the first frost and when the foliage starts to yellow. At this point, daylilies are entering dormancy, which makes them more tolerant of being divided.
- Step 2: Dig up the entire clump of daylilies using a spade or garden fork. Gently separate the clump by hand or with a sharp knife. Each division should have healthy roots and a few shoots.
- Step 3: Replant the divisions immediately in well-prepared soil, making sure the crown of the plant (where the roots meet the shoots) is level with the soil surface. Water thoroughly after planting to help the plant establish itself.
2. Hostas (Hosta spp.)
Hostas are prized for their lush foliage and are often used to brighten shaded gardens. Over time, they can develop large, sprawling clumps, with the center of the plant dying out. Dividing hostas in the fall can help rejuvenate them, promote healthier growth, and keep the plants from becoming too large or congested.
How to Divide Hostas in Fall:
- Step 1: Wait until the hosta leaves begin to die back in late summer or early fall, signaling the plant’s entry into dormancy.
- Step 2: Dig up the entire clump carefully. Use a spade or sharp knife to divide the plant into smaller sections. Each division should have at least one healthy root and a portion of the crown.
- Step 3: Replant the divisions right away in a shady, moist area, as hostas thrive in these conditions. Water the plants well and keep the soil moist as the roots establish themselves over the next few weeks.
3. Iris (Iris spp.)
Irises are a robust and beautiful perennial, but as they grow, they can become overcrowded, resulting in fewer blooms. Dividing irises every 3-4 years helps to maintain their vigor and can give you more plants to share with others. Fall, after the blooming season, is the best time to divide irises, as they are entering a period of dormancy.
How to Divide Irises in Fall:
- Step 1: After the bloom period ends in late summer to early fall, dig up the iris clump carefully.
- Step 2: Gently separate the rhizomes (the thick, horizontal stems) by hand or with a sharp knife. Each section should have a healthy fan of leaves and a well-developed root system.
- Step 3: Trim the leaves back to 6-8 inches. Replant the divisions immediately, ensuring the rhizomes are planted just below the soil surface. Water well after planting to promote healthy root growth.
4. Peonies (Paeonia spp.)
Peonies are known for their spectacular, fragrant blooms, but they are slow to establish and don’t need frequent division. However, older peonies can benefit from division, which helps rejuvenate the plant and encourage stronger flowering. Fall, after the foliage has died back, is the best time to divide peonies.
How to Divide Peonies in Fall:
- Step 1: Wait until the peony has gone dormant, usually in late fall. Carefully dig up the plant, being mindful of its deep roots.
- Step 2: Using a sharp knife or spade, cut the rhizome into sections. Ensure each division has at least 2-3 “eyes” (buds) on it, as this is necessary for the plant to flower.
- Step 3: Replant the divisions, ensuring the eyes are just below the soil surface. Peonies won’t bloom if planted too deep, so be mindful of their planting depth. Water well after replanting.
5. Shasta Daisy (Leucanthemum x superbum)
Shasta daisies are hardy and produce cheerful white blooms throughout the summer. Over time, the plants can become leggy and the center may die out, which reduces their overall appearance and flowering potential. Dividing Shasta daisies in the fall helps to restore their compact shape and encourages fresh blooms come spring.
How to Divide Shasta Daisies in Fall:
- Step 1: Wait until after the blooms have faded and the plant is entering dormancy, usually in late summer or early fall.
- Step 2: Dig up the entire plant and carefully separate the root clump. Use a spade or your hands to divide it into smaller sections.
- Step 3: Replant the divisions right away, spacing them about 18-24 inches apart to give the plants room to grow. Water the divisions well to help them settle into their new locations.
6. Lavender (Lavandula spp.)
Lavender is a drought-tolerant perennial with a pleasant fragrance that thrives in full sun and well-drained soil. While lavender doesn’t need frequent division, older plants can become woody and less productive. Dividing lavender in the fall, after the growing season has ended, can help revitalize the plant and improve its flowering potential.
How to Divide Lavender in Fall:
- Step 1: Wait until the plant has finished blooming and the weather has cooled down, but be sure to divide before the first frost arrives.
- Step 2: Carefully dig up the lavender plant, using a spade or fork to loosen the soil around the roots. Cut the plant into smaller sections, ensuring each section has enough roots to establish itself.
- Step 3: Replant each section in a sunny, well-drained location. Lavender thrives in dry, slightly alkaline soil, so choose a location with these conditions. Water well after planting and prune back the foliage to help the plant establish roots.
7. Coral Bells (Heuchera spp.)
Coral Bells are known for their colorful foliage, ranging from rich purple and red to vibrant green and silver. These plants can become congested over time, leading to decreased vigor and fewer blooms. Fall is an excellent time to divide coral bells, as it helps rejuvenate the plant and spread color throughout your garden.
How to Divide Coral Bells in Fall:
- Step 1: Wait until the flowering period has ended and the foliage starts to die back in late summer or early fall.
- Step 2: Dig up the plant carefully and divide the root ball into smaller sections. Each section should have some healthy leaves and a portion of the root system.
- Step 3: Replant the divisions immediately, spacing them according to the plant’s growth habits. Water the divisions thoroughly to help them establish roots.
Tips for Dividing Perennials in the Fall
While dividing perennials in the fall can be highly beneficial for many plants, there are some important tips to keep in mind to ensure success:
1. Time It Right
Timing is perhaps the most important factor in the success of dividing perennials. If you divide your plants too late in the fall, they won’t have enough time to re-establish their roots before the ground freezes, which could lead to poor growth in the spring or even death. Conversely, dividing too early may expose the plants to early frosts, stressing them out and hindering their ability to thrive.
How to Time it Right:
- Ideal Timing: Most gardeners recommend dividing perennials at least 4-6 weeks before the first expected frost in your area. This gives the plants enough time to acclimate and root before the cold sets in.
- Watch for Dormancy: Perennials should be divided once they’ve started to wind down their growing season and enter dormancy. This usually happens after blooming has ended and foliage starts to yellow or die back. You can check with local gardening resources or your climate’s average first frost date to estimate the best time to divide.
- The Importance of Early Fall: Early fall, after the last bloom but well before freezing temperatures, is typically the best time for division. In this window, the plant is still actively developing roots, which allows it to establish itself and get ready for the winter months.
2. Use Sharp Tools
Using the right tools is essential to ensure that the division process goes smoothly and that your plants are not damaged. Dull or improper tools can cause ragged cuts or stress the plant, potentially making it more susceptible to diseases or pests.
Choosing the Right Tools:
- Sharp Spade or Garden Fork: For digging up clumps of perennials, a sharp spade or garden fork works best. A fork is particularly useful for getting beneath the roots without causing too much disturbance to the surrounding soil.
- Sharp Knife or Pruners: Once the plant is out of the ground, you’ll need a sharp knife or pruning shears to divide the clump into sections. A clean, sharp cut helps the plant heal quickly and reduces the risk of introducing disease to the cut areas.
- Avoid Rusty or Dull Tools: Rusty or dull tools can leave jagged edges, which invite infection and slow the plant’s recovery process. Make sure your tools are sharp, clean, and disinfected before you begin dividing.
- Safety First: When using knives or pruning shears, take care to avoid injury. Always use tools that are comfortable and allow for good control.
3. Water Well
After dividing perennials, it’s important to help the newly divided plants re-establish their root systems. Since the plant has just undergone a stressful process, watering properly is crucial for minimizing transplant shock and encouraging root growth.
Watering Tips for Divided Perennials:
- Thorough Watering: Once you have divided and replanted the perennials, water them deeply. This helps to settle the soil around the roots and ensures the plant has enough moisture to begin growing new roots.
- Moist, Not Soaked: While it’s important to keep the soil moist, be careful not to overwater, as this can lead to waterlogging and root rot. Ensure that the soil has good drainage to prevent standing water around the roots.
- Check Regularly: Continue to monitor the moisture level of the soil as the plant settles in. In drier conditions, you may need to water a bit more often, especially during the first few weeks after division.
- Watering Frequency: Once the plant has re-established roots, you can start watering less frequently, allowing the soil to dry out a little between waterings. This mimics natural rainfall patterns and encourages deeper root growth.
4. Mulch After Planting
One of the best ways to protect newly divided plants through the fall and winter months is to add a layer of mulch around their base. Mulching helps maintain consistent soil moisture, insulates the roots against temperature fluctuations, and can even protect the plant from potential frost damage.
Benefits of Mulching:
- Moisture Retention: Mulch helps to retain moisture in the soil, reducing the frequency of watering during dry spells. As temperatures drop, the moisture in the soil is less likely to evaporate, keeping the roots hydrated.
- Temperature Regulation: Mulch acts as an insulating blanket, helping to regulate the temperature around the plant’s roots. In regions where the ground can freeze, mulch can help protect the roots from freezing by creating a barrier between the soil and the colder air.
- Weed Prevention: A thick layer of mulch can also help prevent weed growth by blocking sunlight from reaching weed seeds. Weeds can stress plants by competing for water and nutrients, so keeping them at bay will give your divided perennials the best chance to thrive.
- What to Use: Organic mulches, such as shredded leaves, bark, straw, or compost, work best. They break down over time and add nutrients to the soil as they decompose. Aim for a 2-3 inch layer of mulch around the plant, but be careful not to pile it directly against the stems, as this can encourage rot.
5. Avoid Dividing Too Often
While dividing perennials is a great way to refresh and propagate plants, it’s important not to divide them too frequently. Some plants are better left to grow undisturbed for a few years, while others may require division more regularly. Dividing too often can cause stress to the plants and affect their ability to thrive.
Guidelines for Division Frequency:
- Hostas and Daylilies: These plants can generally be divided every 3-4 years. Dividing them too often can cause them to become weak, with reduced flower production and smaller leaves. Dividing at the right time ensures that they remain vigorous and continue to grow beautifully.
- Peonies: Peonies, on the other hand, should only be divided every 6-7 years. They take time to establish and may not bloom as well if divided too frequently.
- Overcrowded Plants: While most perennials benefit from occasional division, they shouldn’t be divided if they’re not overcrowded or suffering from issues like disease or poor growth. Only divide when you notice that the plant has become crowded or is showing signs of declining health.
Signs That Division Is Necessary:
- Reduced Blooms: If your plants are producing fewer flowers than usual, it may be time to divide them. Overcrowded roots can limit the plant’s ability to produce blooms.
- Dead or Sparse Centers: For clumping perennials like daylilies or irises, if the center of the plant starts to die out while the outer edges remain healthy, it’s a clear sign that division is needed.
- Slow Growth: Plants that have stopped growing or are putting out fewer leaves or flowers than usual could benefit from division to revitalize them.
Final Words
Dividing perennials in the fall is a fantastic way to rejuvenate your garden, create more plants, and ensure that your flowers continue to thrive for years to come. From daylilies and hostas to peonies and lavender, many perennials benefit from division in the fall, helping them stay healthy and vigorous. Remember, timing is key—make sure to divide before the first frost, and use sharp tools for a clean cut. With proper care and attention, your garden will flourish next spring with fresh, healthy perennials. Happy gardening!