The Why, When and How of Dividing Perennials
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Spring time is the best time to divide many perennials. Here's some quick advice on dividing some of your garden favorites.
Why
Dividing perennials helps the plants in many ways:
- Stimulates new growth
- Controls the size of the plant
- Reduces chances of disease
- Reduces competition for resources
- Give you free plants!
When
Timing varies, but most plants are divided in the spring or fall, when they are just waking up or headed toward dormancy. Choose an overcast day to reduce stress on the plants and water them well a day or so before digging them up. If you divide in fall, make sure plants have at least 4 - 6 weeks to acclimate before frost sets in.
Benefits of Dividing in the Spring
- It's easier to see what you're doing when leaves are just emerging, especially for plants like hostas with large leaves.
- You do less damage to the plant in the spring.
- Spring rains help plants recover more quickly.
- Plants grow rapidly in the spring, which will help them recover quickly.
Benefits of Dividing in the Fall
- The plants are easier to find!
- Fall is a little less hectic in the garden. You may have more time and energy to focus on dividing plants.
How
- Dig up the plant, being careful to minimize damage to the root system. This is a traumatic experience for plants and too much damage can kill them. (Tip: Plants in pots are easier to unearth and divide. Think about keeping some of your favorites in pots permanently so that you have an easy-to-access stock of plants to multiply year after year.)
- Shake off or wash off any loose dirt.
- Divide the plants, being as gentle with the root system as possible. Depending on the type of plant, this may mean cutting the plants apart with garden shears, pulling the root systems apart by hand, or for larger root systems, dividing them with a shovel or garden fork. Plants with fine, delicate roots should be separated by hand. Plants that tend to clump should be separated with a knife or shears. Large, woody stems may have to be separated with a shovel or set of garden forks. Start small until you get used to the process and work your way up to more complicated plants!
- After they are divided, get them planted ASAP. Get them back in the ground or in pots as quickly as possible so that they can recover from being uprooted. Make sure they get plenty of water while they get acclimated.
Cheat Sheet for Some of Your Favs
|
Allium |
Divide annually as needed if the clusters are overcrowded. Replant immediately. |
|
Astilbe |
Divide every 1 - 3 years. Astilbe will bloom best if it is divided regularly. Have a sharp knife on hand; these can be tough to cut through if they are very large! |
|
Daylily |
Daylilies can get overcrowded quickly. Divide every 3 - 5 years to promote more blooms. |
|
Delphinium |
Divide every 1 - 3 years. Avoid dividing these in the fall; they will often die over winter in harsher climates. |
|
Coneflower |
Divide every 4 - 5 years to promote healthy plants. Again, you'll need a sharp knife to divide these if they are very large. |
|
Hosta |
Separate these in spring before the leaves unfurl. As you get to the center, cut out any bare or dying areas so your plants have a fresh start. |
|
Bearded Iris |
Divide every 1 - 3 years. You'll know these need dividing when you see fewer blooms on the plants. Cut the rhizome into 3 - 4" section, making sure each section has a fan of leaves. Discard any older sections. |
|
Stonecrop |
Divide every 4 - 5 years. These can be fragile, so divide by hand. |
Keep in mind that you can divide plants more frequently if you want to add to your garden stock without buying new plants. Just make sure they have enough eyes/shoots/roots at the time you divide to survive!
Happy Gardening!