- Division should be done when shoots have quit growing at the center of a mature clump. This will greatly improve the plant’s appearance. Lift the entire clump and rinse excess soil from the roots. This will make it easier to see where each cut should be made. Use a sharp knife to make the divisions. Each division should have at least 2-3 eyes.
- Spring is the easiest time to divide Hostas because new shoots are only a few inches high and the leaves have not expanded. Varieties in the Sieboldiana or Tokudama families should not be divided in spring as new roots will not grow until the foliage has fully expanded and hardened off. During this period, the leaves may desiccate quickly on warm days, since the roots have been reduced in size or were injured during division.
- Though spring division is easiest, summer division is preferred and can be done in August, at least 30 days before the first fall frost date. Warm soil and higher humidity at this time promotes better root growth, and plants may put on a little growth spurt at this time.
- Keep newly divided plants well-watered the first two weeks, especially during periods of drought. Some of the larger leaves on a division may be cut back to reduce water loss. Frequent division of a clump will restrict plant and leaf size, and keep it from developing to its desirable mature features.
