Divide and transplant Hostas
Spring may be the easiest time to divide hostas, before their foliage emerges. Spring is not a bad time to divide most hostas, especially those that multiply fast and are in the greatest need of division. But there are risks.
Hostas are dormant through the winter, and are less likely to develop new roots than many other perennials. Spring leaves emerge, expand and harden off in about three weeks, depending on the weather. New root growth starts after the first foliage hardens off. Cool spring soil temperatures may slow or delay this root formation even longer.
The danger of dividing hostas is a cool weather spring, when the soil is slow to warm. Newly divided hostas may have large mature leaves and no new roots for weeks. Beautiful spring days of bright sun, cool breezes and low humidity, are very stressful for recently divided hostas. On those days the desiccation rate is very high, and the new hosta divisions, with their reduced and possibly damaged root systems, will dry out rapidly. If the weather turns hot for even a day or two, the hosta leaves may burn. While this damage may not prove permanent, this yearâs growth will certainly be reduced.
If hostas are divided in the spring, do not over divide them. Avoid dividing H. sieboldianas and 'Tokudamas', or at most split slow growing clumps in half or quarters. Fast growing cultivars recover more quickly and can be divided a little more. Dig them with a garden fork, not a shovel, so their long roots are damaged as little as possible. Hosta roots only grow at the tip, cut roots rarely branch and get any longer. New roots will have to develop to take their place.
The best time to divide hostas may be in August or early September, at least 30 days before the first frost date. After their summer heat dormancy, many hostas begin to actively grow again and fall season conditions are good for root growth. The soil is warm and the air is usually more humid than in the spring.
The primary danger dividing hostas in August is excessive heat or extended drought. Do not let newly divided hostas dry out for the first two weeks. Removing some of the older, larger leaves or cutting the foliage back at the time of dividing will reduce water loss. Any leaves that suffer burned edges will be taken by the frost in a few weeks anyway.
Newly planted hostas need an inch of water a week.
1. Get the right tools for your soil. You will find it easiest and safer to use a garden fork with flat blades rather than a spade or shovel.
2. Dig around the hosta plant, starting 6 to 18 inches from the base, depending on the clump size. Once you have cut a circle around the clump, loosen some of the soil within the circle and gently lift the hosta out of the ground.
3. If you are new at dividing hostas or other perennials, washing the dirt off the clump can be helpful to see the individual plants and their rhizomes (from where the roots grow). Also wash the plant if you are unsure of how the individual plants are growing and you don't want to slice one in half (particularly if the hosta is a slow-growing expensive one). Do not worry about damaging the roots with the water, because hostas' roots are tough.
4. If possible, separate the individual plants by hand, by gently forcing your thumbs between the stems, and easing the stems apart. To remove a stem from the crown, use a back and forth pulling motion and not a side-wise motion (hold the core plant in one hand, and grab the stem in the other, rotate the stem-holding back and forth), work the stem back and forth until the rhizome comes loose or breaks from the crown. The rhizome will break at the appropriate point.
5. If the clump is very large or for some varieties, it may just be easier to use the serrated kitchen knife to cut through the clump. Cut the clump in various sizes, in half, into thirds, or quarters.
6. Start by spreading the roots so that you determine where you want to cut. Try to keep as many roots and stems as possible, by making cuts through the crown but not into the roots. Start by cutting the crown in half, if you are really careful you can navigate around the stems; if the clump is really large, sometimes it is just easier to cut in half, without much concern about losing a few stems.
7. If possible, make the cut about half way through the crown and then see if you can pull it apart by hand; use the same back and forth pulling motion. In this case, hold each half in one hand, and gently rotate the halves in opposite directions, then rotate back and forth each time applying a bit more pressure and simultaneously exerting pressure to move the halves away from each other. If you can't pull it apart then make the cut deeper.
8. Washing between cuts to remove soil can improve your insight into how the plantâs stems are growing, and to see where to cut or pull apart.
9. Remove some older, larger leaves or cutting the foliage back at the time of dividing will reduce water loss and help to minimize shock.
10. Plant the divided plants. Do not think that a small piece might not grow. It's amazing how resilient these plants are and you might as well plant the little pieces alongside a larger plant. 11. Do not let the roots dry out too much. If you cannot plant them right away, place some moist dirt or peat moss on the roots and store them away from sun light.
12. If the plants' roots dry some before you get a chance to replant, soak the plant in a bucket of water for two hours.
13. For stem divisions resulting from pulling plants apart and which have a nice balanced root distribution, plant these divisions at their original level, so that the white basal portions of the stems are just under the ground and you cannot see them. If you have washed the roots or the roots are not holding much soil, make a good size hole and spread the roots out in a fan. Replace the soil, pressing firmly with the heel of your hand around the plant, and water the plants well so no large air pockets in the soil exist.
14. If you had to use the knife to cut the clump, plant these smaller now-divided clumps at the same height as they were growing, or just slightly deeper and water in well.
15. Make sure newly divided hostas receive water every few days during first two weeks.