When Can You Divide Hostas?

Shade-loving hostas provide an attractive option in areas where few other plants thrive. Perennials in United States Department of Agriculture hardiness zones 3 through 9, hosta types vary widely, from those with solid-colored blue-gray leaves to yellow variegated varieties. Dividing hostas is a simple task that requires no more than a shovel and a sharp knife.

Hostas grow on a rhizome -- an underground stem that multiplies. The leaves emerge from this rhizome from a bud. Digging up a hosta that is several years old will produce a large clump of rhizomes, which are split to produce multiple plants. There are several reasons to split hostas.

Plants are overgrown: When hostas are too big for a space, they should be divided. Although it takes a long time for hostas to become root-bound, it is always better to give a plant plenty of room so it does not become stressed.

Plants are damaged: Hosta rhizomes can become damaged from digging dogs or wayward walkers. Removing the damaged section of rhizome will prevent disease from taking over and spreading to the rest of the plant.

Sharing plants: You can also divide hostas to share plants with a friend or to add to another garden.

As hostas break dormancy in the early spring, the tips of leaves emerge through the surface of the soil. This is the best time to split hostas. Because leaves have not fully emerged from the rhizome yet, they cannot be damaged during the splitting process. Dividing rhizomes requires some force, so cuts and tears and damage will be visible on the leaves.

Although early spring is the ideal time to divide hostas, they can be divided any time after they break dormancy in the spring until early summer. Avoid splitting hostas during the hottest part of summer, July and August, as it can be too hot and dry for plant roots to recover from being divided. Fall is not an ideal time to split hostas because they must have plenty of time to recover from plant division before they go dormant in the winter. For best results, make all hosta divisions before July.

Use a shovel to loosen the soil around the base of the hosta about 8 inches deep. Work in a circle around the plant, 6 inches away from the outside leaf spikes, at the start of the season, or leaves if they've opened already. The soil should be loose all the way around the plant before pulling up the rhizomes.

Wearing gloves to protect from insects or sharp items, feel for the outside of the rhizome ball in the loose soil. Then place one hand on each side and lift it out of the soil. There may be some resistance from roots when pulling up the plant. Give it a gentle pull to remove the rhizome ball from those roots; this will not hurt the plant. Gently knock the excess soil off the clump.

Determine where cuts will be made. Each division needs two to three leaf buds to ensure growth after it is transplanted.

Sterilize a sharp knife or trowel with an alcohol wipe to prevent the spread of disease. Cut each section at the predetermined spot by firmly moving the knife over the rhizomes. Although they are firm, they are quite easy to cut.