Not sure when to divide hostas? Discover tips for dividing these dependable perennials.
Tackle dividing hostas with confidence by learning a few basics tips on technique and timing. The most important question to ask before grabbing your spade is why you’re considering dividing hostas. If you simply want more of a given plant, you might be able to avoid digging the whole clump by splitting hosta starts, or young plants, from around the outer edges of an existing plant. If you have a plant that’s dying in the middle or is clearly suffering in some fashion, dividing may be the only option.
The general rule of thumb on dividing hostas is to avoid it all costs, at least with the larger to giant varieties, like Hosta ‘Sum and Substance’ or Hosta ‘Big Daddy.’ Providing growing conditions are ideal, larger hosta varieties only improve with age. Many of these larger types don’t even start to hit their stride until they’re five years old. Dividing hostas like these actually limits their growth potential, reducing their overall size. For miniature varieties like Hosta ‘Blue Mouse Ears,’ splitting hostas can actually help plants maintain a tidy, tiny size.
When to divide hostas is simple. Two times of year provide the best conditions for digging and transplanting hostas: early spring or early fall. Either timeframe yields roughly a four-week window that’s ideal for splitting hostas. Wait too long in spring, and your recently dug hostas will encounter hot summer temps, which reduce chances of survival. Wait too long in fall, and winter cold can kill plants.
To hit the timing right for dividing hostas in spring, aim to get plants dug between the time that hosta shoots first appear and before leaves start to unfurl. In fall, aim to dig hosta varieties starting one month before your region’s average first frost date. In more northern areas, that would likely be the month of September; for warmer zones, October.
Make sure soil is most before you start splitting hostas. If you haven’t had rain, water plants a day or two before you plan to dig. Before digging, it’s important to understand that hosta roots grow at the tip only. If you slice through many roots while dividing hostas, those roots won’t grow longer or branch at the cut. Using a digging fork to loosen and lift hosta plants from soil can help prevent cutting roots.
To lift an entire plant and separate it into several viable divisions, insert your digging fork or spade into soil outside the dripline of the leaves. Work your way around the plant, eventually prying the plant from soil. Lift the plant free from soil and shift it onto a tarp. Divide hostas into pieces with eyes or growing points. Some hostas pull easily into divisions, while others need cut with a sharp spade or knife.
Replant divisions in soil with plenty of organic matter. Set divisions at the same depth they were growing previously. Water thoroughly after planting to ensure that the roots have readily available moisture.