How to Divide and Transplant Native Perennial Plants
A few weeks ago, I had the privilege of attending an informative workshop on dividing perennials at the Native Gardens of Blue Hill. Led by Daksha Baumann, an experienced, local, professional gardener, the workshop covered the fundamentals of dividing and transplanting perennials in the garden and allowed attendees to get their hands dirty with hands-on instruction on plant division.
It’s always wonderful having fellow gardeners and plant enthusiasts attend the NGBH workshops, and we hope that you can stop by our upcoming events this summer. But if you missed out on learning about plant division, no fear! Using Daksha’s gardening tips, we’ll walk you through the basics of dividing native perennials right here.
How do you know if perennials need to be divided?
Not all perennials necessarily need to be divided, but dividing plants can rejuvenate their growth and make more space for other plants in a garden bed.
Some of the key signs it’s time to divide native perennial plants are that your plants may look overgrown, bushy or tangled. Different perennial plants may also be growing into each other, or they may be swamped with weeds that are sprouting in between the plant’s roots and leaves. Perennials can also flower less and appear less vigorous or develop bald or open centers in the clump, which are all clear signs it’s time to divide!
Why divide perennials?
Dividing perennials can take a bit of work and elbow grease, but it’s worth it! Some of the key benefits of dividing native perennials include:
Perennials come back year after year, and they often spread over garden beds as they grow. But when this occurs, the growth of nearby plants can be impacted as they compete with each other for space, moisture and nutrients. This can slow their overall growth or cause other issues, like reduced bloom size and number. When perennials are divided, however, it eliminates competition between plants and enhances their growth too!
Some perennials can develop bald spots at their center as they spread outward when they need to be divided, such as Joe Pye Weed. Dividing perennials can improve the vigor of your plants, and the act of division makes it easier to remove weeds at the same time.
Control plant size
As they age, some native perennials can get quite large and they can overwhelm a smaller garden bed. Dividing your plants reduces the clump size and and can stop vigorous growers from spreading into other nearby plants.
When you divide perennials and replant them in your garden, you’ll naturally improve the air flow around your plants. Since many plant diseases, like powdery mildew, thrive in areas with poor air flow, dividing perennials is one easy way to reduce the spread of plant diseases in your garden.
One of the main perks of dividing perennials is that it provides you with even more plants for your garden. When you’ve divided your irises, coneflowers or ferns, you can plant the divisions around your garden or share them with friends. And, if you love to garden, what’s better than free plants!
When to divide perennials
Different perennials need to be divided at different times of the year, so it’s important to research the particular plant you’re working with to determine when it should be divided. Some perennials also need to be divided more often than others, although most perennials benefit from being divided every 3 to 5 years.
If you’re in doubt about a particular plant, there are many online resources for suggestions on when to divide particular perennial plants, or you can browse the shelves of your local library or bookstore for a quality gardening book that contains that information as well. However, as a general guideline, the following tips can help you pick the right time of the year to divide your native plants:
Plants that flower in spring to early summer should be divided in autumn. Dividing plants when they aren’t flowering will channel more of your plant’s energy toward its root system. Examples of native plants that should be divided in autumn include blue flag iris and golden groundsel.
Divide plants in fall no later than 4 weeks before your first frost date. Dividing plants weeks before frost helps plants get established before the cold weather arrives.
Plants that flower in late summer to autumn should be divided in spring. This includes plants like bee balm and blue lobelia.
Divide plants on overcast days. Plants are less likely to be stressed when they’re divided on cool, overcast days.
Divide plants before rain. Performing plant division right before rain will help your plants settle into your garden more quickly and it will also reduce planting stress. Not to mention, you won’t need to water your new plants as much!
Don’t divide plants during hot, sunny weather. Dividing plants during hot weather and bright sun is more likely to cause wilted leaves and other signs of plant stress.
Of course, as gardeners, we know that sometimes our gardening schedules and the weather won’t cooperate, and you may need to divide your perennials at other times of the year. While this isn’t ideal, most plants are adaptable and will still be able to bounce back after they’re divided and transplanted. Just make sure your plants are watered well after transplanting and don’t divide plants in very hot weather to reduce the likelihood of transplant shock. Cutting them back after division can prevent them from wilting.
How to divide perennials
Different perennials may require slightly different techniques to divide them but, in general, the steps below should work for most native plants. Even better, plant division is incredibly simple to do, and it doesn’t require any “fancy” tools beyond a shovel, pair of digging forks, gardening knife or pruners and maybe some spare pots and a tarp.
1. Choose the right time to divide. As mentioned above, different perennials will need to be divided at different times of the year, but spring or fall tend to be the best times for plant division. If possible, divide your plants on an overcast day before rain is expected. This will help your transplants transition into your garden more readily.
2. Water your garden well. The day before you plan on dividing perennials, water your plants well. This will soften the soil and make it easier to dig up your plants. Additionally, well-watered and hydrated plants are less likely to suffer transplant shock after they’re divided!
3. Dig up your perennials. Using a shovel or gardening fork, dig up the entire root ball of the parent plant, taking care not to damage the root system. Gently lift the plants out of their planting hole, and shake away as much soil as you can if you intend to divide your plants right away. If you aren’t able to replant your perennials immediately, you can repot them in garden pots or lay them out on a tarp in a shady section of your garden and water them as needed until you’re ready to divide and replant them.
4. Divide the root balls. When you’re ready to divide your perennials, there are several different techniques to use, and some techniques may work better than others for particular plants. Plants with roots that aren’t tightly woven together can often be teased apart with just your fingers; however, plants with tough root balls may need to be cut apart with gardening knives, a spade or two garden forks. Garden forks can be particularly useful for tough perennials, like daylilies. All you need to do is dig your plant and lay it on its side, place the two forks back to back in your plant’s root ball, and then pry the forks in opposite directions, which will break the root system in two. If you need smaller sections of perennials, this process can be repeated several times to break up large clumps of plants. When dividing plant roots, be as gentle as possible to minimize damage. Also, make sure that each plant division has a good supply of roots and at least 3 healthy shoots or stems.
5. Remove debris and diseased plant material. As you work, pick or cut out any old or diseased plant matter, and pull out any weeds that may have woven themselves into your perennials’ root systems. If you’re dividing tall plants with long leaves, such as irises and daylilies, you may want to cut the leaves down by about ½. This focuses the plant’s energy toward root development and reduces the likelihood of transplant shock.
6. Replant your perennials. Once you’ve divided your new perennials, they can be planted throughout your garden or potted up to share with friends. When replanting perennials, be sure to follow the recommended planting depth and spacing requirements for the plant you’re working with.
7. Water your plants in. After transplanting your divided perennials, water your plants well and then water them as needed to help them settle into your garden. Some plants may droop slightly after transplanting, but this is normal and usually isn’t cause for concern. For even happier plants, consider spreading a 1 to 3” layer of organic mulch over your garden beds to lock in the soil moisture levels, smother weeds and prevent your new perennials from drying out as quickly, or set up a burlap screen to shade your transplants for a couple of days.
Which native perennials should be divided?
Many native perennials will benefit from being divided every few years. The best way to decide if a particular plant needs to be divided is to research the plant a bit and keep a look out for signs of stress, such as reduced blooms or bald plant centers. Some perennials that often benefit from division include:
Ferns, such as maidenhair ferns and cinnamon ferns
Blue flag iris
Joe Pye weed
Dividing perennials can seem intimidating at first, but with a few simple garden tools in hand and a bit of confidence, you can master the art of plant division in no time! For more gardening tips, check out our articles on native plants or attend one of our upcoming workshops to learn more.