How to Divide Plants
Published: September 21, 2012
Make the most of your perennials by dividing and transplanting favorites that have outgrown their homes.
Why divide and transplant?
Plants need space to thrive. When they become too big for their garden spots, powdery mildew coats leaves, insects chow down on blooms and stems, and centers become brown.
When you divide and transplant, each perennial — the new and old — blooms more. Plus, divided plants are cheap plants — they fill in garden gaps and are a hit at neighborhood plant swaps.
When’s the best time to transplant?
Transplanting rule of thumb: If it flowers in spring, transplant in fall; if it flowers in fall, transplant when the blossoms fade.
But really, anytime is an OK time to move perennials if you can dig the ground and water the transplants. If you transplant in warm weather, avoid hot afternoons.
Early fall is particularly good because rain is more plentiful in most regions, and roots have an entire winter to grow and anchor themselves into the ground. Some happy fall transplants include:
- Bleeding heart
- Spring bulbs such as tulips and iris
Plants that would rather be transplanted in spring are:
- Black-eyed Susans
Dividing without tears
You don’t need a surgeon’s touch to divide perennials, which are hardier than they look.
“Just dig or pull it out; you won’t hurt it,” says Sheri Ann Richerson, author of The Complete Idiot’s Guide To Year-Round Gardening.
5 essential steps for dividing plants
- Prune the plant by about a third, which reduces its water requirements after transplanting.
- Place a shovel or spade where you want to divide the plant, push the tool down through the plant and roots, and pull up the divided plant.
- When dividing bulbs, dig up the mature plants and gently pull bulbs apart with your fingers.
- To divide hostas, cut roots with a sharp knife or shears.
- Trim the roots of divided plants, which makes them stronger and healthier (just like trimming split ends makes hair healthier).
6 essential steps for transplanting
- Give plants a nice long drink before transplanting. Immerse their roots in a bucket of water with a small amount of fertilizer for at least 30 minutes and no longer than overnight. Place the bucket in a shady place. This will decrease plant stress.
- Amend soil with compost from your pile or a slow-release fertilizer. Bulbs will appreciate a handful of bone meal.
- Dig a hole about twice the diameter of the plant.
- If you’ve got clay garden soil, place crushed gravel or terra-cotta pot shards in the bottom of the hole to increase drainage.
- Place plant in hole and cover with soil.
- Water thoroughly and check every day or two to make sure the soil is moist, not sopping.
- Divide and transplant perennials every 3-5 years.
- Dividing and transplanting temporarily stresses plants, so pick a day that’s not too hot or cold. A mild, overcast day about a month before the first hard frost is best.
- Let plants rest for a couple of weeks after blooming, which is stressful. Then transplant.
- If a heat wave suddenly appears, shade transplants with a beach umbrella and water daily.