The best time to divide hostas is generally in the spring after the shoots have emerged from the soil but before the plants have fully leafed out. At this point, the stems should be several inches high and still tightly formed, often with a purple tone to them. Choose an overcast, damp day if possible.
Hostas are also sometimes divided in summer, although the leaves are usually cut back prior to dividing them. Hostas can also be divided in the fall or winter, provided the soil is not frozen, but the crown and roots may become damaged by freeze-thaw cycles if not yet established in the surrounding soil.
When to divide hostas
Hostas can be divided any time of year, provided the soil is not frozen. That said, results tend to be best when the hostas are divided in the spring or summer. Dividing and replanting the pieces before fall arrives gives the roots at least six to eight weeks to grow and become established in the soil around the planting hole. It also gives the soil a chance to settle and lessens the impact of freeze-thaw cycles on the roots.
Dividing hostas is best done on a rainy or overcast day while the air is somewhat moist. You can certainly divide them on a hot and dry day, but the pieces may experience transplant shock and likely will not root in as quickly as if the roots had been kept consistently moist and cool. If dividing during hot weather, try to do the division and replanting early in the morning before the heat of the day truly arrives.
Dividing hostas in spring
Hostas can be divided in the spring as soon as the soil has thawed and can be worked. Hostas are slower to emerge from the soil than some other hardy perennials (like peonies), so you may wish to wait for the shoots to poke through the soil prior to digging up the plant if you don’t know exactly where it is. Waiting until the shoots have emerged several inches is optimal in terms of timing division. You can also wait until right after the hosta has leafed out to transplant it.
Try to recall how large the particular hosta is while fully leafed out in the summertime. This can be tricky if you’re in a new location and haven’t seen this hosta (or can’t remember what it looks like in midsummer). Miniature hostas usually have very slender, pencil-thin shoots, while giant hostas have thick carrot-like stems.
Dig in a circle around the hosta, at least as wide as the foliage grows, if possible. Pry the clump up from the ground and slice it into half and then into halves again. You can keep dividing it as long as each piece has at least one bud stem. Replant the pieces immediately and water well after planting.
Dividing hostas in summer
Hostas can also be divided in the summer. This is usually after the plant has leafed out and has sent up a flower stalk. At this point, some of the leaves may have become damaged by slugs and other pests, and the plant may not be quite as attractive as it had been earlier in the spring.
Start by marking the size of the plant on the soil to note how wide the foliage grows. This will be helpful when deciding how large of a soil clump to dig out of the ground. Then, cut the entire plant down to about a half-inch (1 cm) above the crown at the base of the plant (where the leaf stems meet the roots). Dig up the clump, slice it into pieces, replant, and water very well. Keep watering the replanted pieces very regularly, especially if the weather is hot and dry.
Dividing hostas in fall
Hostas can be divided in the fall, but they do best when divided in the early fall. Try to get the pieces replanted into the soil at least four to six weeks before the first frost. The pattern of freezing ground at night followed by thawing soil in the daytime can be hard on the roots of newly planted hostas because the roots are very shallow and are not yet anchored into the surrounding soil.
Hostas can be divided in mid or late fall, but beware that they may be damaged by freezing soil conditions as the roots haven’t grown out into the surrounding soil yet. Still, sometimes this is the only time available to divide them. If dividing in fall, replant into the ground and cover with mulch. Alternatively, pot them up into containers and place them in a sheltered cool location to allow them to go dormant without subjecting them to numerous freeze-thaw cycles.
Dividing hostas in winter
Hostas can be divided in winter into regions where the ground does not freeze. The risks of winter division are the same as in the fall. Try to wait until late winter or even early spring to divide the plants if possible. That said, you can certainly divide hostas in winter if the soil is not frozen as long as the plants are replanted carefully, and conditions don’t get too cold in the soil.
