Division

Correct overcrowded roots with division. Not the chalkboard variety, but by digging plants up, cutting them apart, and replanting.

Do my plants need dividing?

If production is down among your perennial plants, it may be that the roots have become too crowded. You can fix that with division. Division is a form of asexual propagation used on perennial plants. Annuals and biennial plants do not live long enough to make this method worthwhile. Signs that your perennials need dividing:

• flowers are smaller and fewer in number
• overall loss of vigor
• the center of the plant is dying
• plants have outgrown an area

Why divide plants?

There are many perennial plants that benefit from dividing every few years. Plants that grow from rhizomes, such as bunch grasses, asparagus, and ginger, can be divided simply by digging up a section of the underground stem and cutting between the established plant and new growth, and planting the cut end someplace else. Many other perennial plants grow from corms and bulbs. These plants reproduce underground by creating offsets and bulbils, respectively. In either case, over time, it gets crowded down there!

Which plants need dividing?

Some plants, peonies and hostas, for example, never need dividing. Others, such as iris, Shasta daisies, and coreopsis should be divided every 2 or 3 years. Daylilies, evening primrose, and bergenia generally need dividing every 5 years or so. Many other garden plants vary in their need for division, depending on soil health, plant age, climate, and more. It’s generally a case of being observant and noticing when plants look like they need some breathing room. Artichokes commonly need dividing, as do many flowers, including chrysanthemum, delphinium, germander, lamb’s ears, penstemon, scabiosa, and yarrow.

When should plants be divided?

Autumn is generally the best time to divide plants. Autumn-blooming plants, such as saffron crocus, should be divided in spring. In both cases, temperatures are neither too hot not too cold, and plants will have time to recover before winter’s chill slows growth to a halt, or the summer sun bakes everything to a crisp.

Overcrowded Shasta daisies

Shasta daisy clusters

Dividing roots of Shasta daisy

Division converts one plant into many

How to divide perennial plants

Don’t be afraid to try dividing your plants. They will be far healthier and more productive once they reestablish themselves. Follow these steps to divide the perennials in your landscape:

1. Prepare plants for their ordeal with a light watering and some gentle pruning the day before you plan on dividing them. Remove any less than healthy twigs and stems and then reduce the plant’s overall size by one-half. By making the plant smaller, you will help it recover from transplant shock. The supporting roots will still be the same size, but the above ground portion that must be maintained will be that much less.
2. Dig carefully around the plant being divided. Try to get as much of the root ball as possible and keep it intact. Gently lift the root ball onto a tarp or a patch of lawn.
3. Using your hands, tickle and tease the roots apart, making sure that each section has both roots and shoots. If the roots are too terribly tangled, you may have to pry them apart with spading forks, or cut them apart with a knife. For monster root balls, place the blade of a shovel over the center of the root ball and give it a good stomp, slicing right through the middle of the root ball. I know, it sounds mean-spirited, but your plant will thank you in the long run. Note: these giant root balls will grow really fast, so they will need to be divided again the next year.
4. Toss any older, withered roots into the compost pile. They are spent. The younger, healthier material should look firm and white.
5. Before returning the divided roots to the same bed, add some aged compost or other organic material to provide a nutrient boost and improve soil structure. Extras can be planted elsewhere in the landscape or in containers to be shared with family, friends, and neighbors. If plants will be out of the ground for very long, they should be placed in a covered bucket (or under the tarp) to reduce drying.
6. After planting, mulch around plants and water well. These traumatized plants will benefit from a little protection from excessive sunlight, wind, or temperature extremes, until they have reestablished themselves.
7. One week later, feed with fish emulsion or some other light fertilizer.

Help your perennial plants reach their full potential by periodically dividing them. By dividing, I transformed my overcrowded, unhealthy, and unhappy Shasta daisy into 15 separate plants that now have room to grow and thrive and bloom!