If you grow perennials in your garden, you’ll soon encounter the need to divide and transplant them. Perhaps they’re overgrown, or crowded, or you’d like to spread them around your garden, or share them with a friend. If done correctly, most perennials can be divided quite easily without harming the plant. Here’s how to go about it.
When to Divide Perennials
The best seasons for dividing and transplanting perennials are spring and fall. Spring is the ideal time to transplant fall-blooming perennials and ornamental grasses, while fall is best for spring-blooming perennials.
Allow the plants several months to become established before their bloom time, in order not to miss a season of color. They also need at least six weeks of growing time before a hard frost. Some gardeners divide right after what seems like the “peak” year for that particular plant.
Look for these warning signs, and divide your plants while they’re still healthy:
- The plant is too large for the space or is crowding other plants.
- Thinning in the center of the clump to a donut shape.
- Fewer flowers, straggly-looking leaves, or weak growth.
Step 1: Get Ready
The day before you plan to divide your perennials, give them a good soaking with water to help them stock up and survive the shock of transplanting. If the plants are tall, you may want to cut them back a third to prevent breakage and help conserve energy.
Next, gather your tools. You will need:
- Work gloves
- Shovel or spade
- Two pitchforks, or a clean sharp knife
- Soil conditioner or compost
- Wheelbarrow or tarp for transporting
Step 2: Dig ‘Em Up
How you divide perennials depends on the growing habits of the particular plant:
Clumping Perennials: (daylilies, chrysanthemums, asters, hostas) These plants typically grow from one main crown. The crown gets larger and larger each year, and sometimes you’ll see offsets (baby plants) attached to it. These plants are easiest to divide if you dig them up completely, so you can separate and divide the crown.
Spreading Perennials: (bee balm, phlox, leadwort, perennial vinca, gooseneck loosestrife) These plants grow by surface or underground roots, or by dropping seed. They look more like a grouping of individual plants, each with its own crown and root system. You can divide these plants simply by digging up the ones you want to move while leaving the rest alone.
Woody Perennials: (lavender, rosemary, candytuft, euonymus) These plants tend to have just one main stem or trunk, but they often spread when a stem touches the ground and takes root. You can sever and dig up the new plant without disturbing the original plant.
Taproot Perennials: (oriental poppies, balloon flowers, butterfly weed) These plants have one main, deep root. To divide them, you must dig up the plant and cut it so that each division has a piece of the taproot along with some growth buds.
Here’s where you have to be fearless by following these steps:
- Using a shovel or sharp spade, slice deep into the earth in a circle, at least 6” from the crown of the plant to severs the roots.
- Work your shovel underneath the clump, and pry it out of the ground. The root ball will be almost as big as the plant itself, and try to dig up as much of it as you can. Use a combination of prying and pulling to work the entire root ball loose without breaking the stems.
- Pull or carry the plant onto your wheelbarrow or tarp, so you don’t trample your other garden plants.
Step 3: Divide
If your perennial is the clumping type, you now need to divide it. Pull or cut apart the crown into 3-4 chunks. Each chunk should have several stems and a nice clump of roots. Larger clumps will become established faster, and bloom sooner, than smaller ones. As a general guide, you can expect next year’s plant to be about as wide as the newly-divided root ball.
For large plants, you can put two pitchforks through the middle, and pry the plant apart. I like to use my hands and a sharp knife to divide the clump, so I can have more control over the amount of roots going with each division. But for large, tough plants, I’ve even used an ax to chop it in two!
Don’t be afraid to break some roots, but try to follow where the plant naturally seems to split—sometimes they’ll even fall into pieces on their own. Discard any diseased or broken pieces; only keep the healthiest parts of the plant.
Step 4: Replant
Now you’re ready to replant your perennials! After the trauma of digging and ripping apart your beloved plant, you can see how important it is to baby them in their new home. Follow these steps:
- Dig a hole as deep as, and a little wider than, the root ball.
- Mix in plenty of organic matter and sprinkle a source of phosphorus, such as bone meal or 0-19-0 fertilizer, in the hole to promote root growth.
- Place the division in the planting hole. Make sure the roots are spread out and down – you don’t want downward-growing roots to be turned upward in the hole, or sticking up out of the ground.
- Fill in around the plant with soil, tamping it gently down. Make sure the new plant is planted at the same depth as it was originally.
- Water the plant well, and feed regularly with a balanced organic fertilizer. Water about every other day for the first 2-3 weeks. I like to baby my transplants with a little extra water for the rest of the growing season, particularly if they’re planted in a spot that doesn’t receive regular water.
- Add mulch around the plants to insulate the roots and hold in moisture.
Newly divided perennials usually look pretty ugly until the next season, so focus on getting the roots properly settled and the crown nice and straight.