How (And When) To Divide Hostas In 5 Steps

PERENNIALS > HOSTA > DIVISION

Hostas are incredibly useful plants to grow in your garden and knowing how and when to split them makes it easier to keep them healthy and increase your collection.

They are a well-known ornamental shade plant, forming elegant clumps and sometimes reaching impressive sizes.

This plant is commonly grown for its attractive foliage, which can come in a range of different hues and with variegation.

If you have some shady or partially shaded spots in your garden, hostas can be an excellent choice.

However, Horticulturist Peter Lickorish warns: “As with many perennials, clumps of hostas can develop a bare centre and patchy growth if not divided regularly.

“If the clump is treated like a pie, slices of the pie can be lifted, each with only a small piece of the older, weaker central growth.”

Why Split Hostas?

“Most hostas, depending on the look you want, can live a long time without dividing,” says David Teager from the Delaware Valley Hosta Society.

“They look best as big, mature clumps. However, if you wish to maintain a tidy edging of hostas, it will be best to dig them up every 3-4 years and divide them.”

“Hostas generally grow to the space that you give them but you will have some varieties that will be stronger than others,” explains Ollie Walker from Sienna Hostas.

“These may need dividing in order to give the slower-spreading varieties space.”

Generally, hostas are split for two main reasons:

1) Preventing Overcrowding

The first is to prevent overcrowding in perennial planting schemes and keep mature plants healthy.

“If left undisturbed, giant hostas can reach a clump size of over 2m in diameter,” shares Sue, the Owner of Sue Proctor Plants.

As Sue explains, hostas spread to form large clumps over time, and may outgrow the position in which they were initially placed.

“Hostas can live with being overcrowded for quite a while but this can affect their mature dimensions,” says Melanie Collins, a Partner at Mickfield Hostas specialist nursery.

“Many varieties, even small ones, can have a decent spread if they’re allowed to develop outside of the confines of a container.”

When a hosta plant grows large, it can become crowded, and may reduce in vigour as it outstrips water and nutrient resources available.

Other plants in the vicinity may also suffer when perennial plants in mixed plantings are not divided, as Robert Barlow from North Staffordshire Hostas explains:

“Dividing hostas helps keep them more compact, allowing you to grow them in a specific garden space.”

“Hostas are like any other herbaceous perennial; they effectively grow in size around the outside of the crown,” says the owner of Rewela Hostas, John Plant. 

“Eventually, the centre of the crown dies off. It is important to re-invigorate by splitting your hostas, which will also create younger, healthier plants.”

2) Propagating New Plants

It allows you to propagate new plants – and is an incredibly easy and completely free way to do so.

When you split hostas, you get free new plants to place elsewhere in your own garden, or to give, perhaps, to family or friends says John from Rewela Hostas.

Dividing hostas and other existing perennial plants in your garden is also a more sustainable and eco-friendly solution when populating new beds or filling new garden areas.

Since you will not have to purchase any new plants in plastic pots, you can reduce your negative impact on the environment.

If you are new to plant propagation, then dividing perennial plants like hostas is a very simple, straightforward place to start.

When To Split Hostas

“If you want to divide Hostas, they can be divided at any time during the growing season, but it is usually best to do your dividing between the spring and early autumn, especially when dividing miniature hostas,” explains Barry Ankney from the American Hosta Society.

Summer-flowering plants more broadly, including hostas (even when flowers are not produced on all cultivars), are best divided in spring (March to May) or in the autumn (September to November) because water is generally more accessible in the soil, and cooler temperatures reduce plant stress. 

“Dividing your hostas is best done in spring when the pips are just emerging,” David suggests.

If the autumn is particularly wet, it may be better to delay division until the spring to reduce fungal problems and prevent plants from rotting.

You can also split hostas over the summer, but the strain on the plants will be increased during hot and dry weather, so consider thinning a third of the foliage.

How Often Should You Split Them?

You can split mature hostas to make new plants any time after an existing clump is well-established.

For health and to prevent overcrowding, you will usually split hostas every 4-5 years.

Hostas grown in containers may obviously outgrow their containers and need to be split more frequently as Robert shares:

“Hostas grown in pots should be divided every 3-5 years.

“You can tell when this needs to be done from all the new shoots that appear to be growing around the edge of the pot.”

How To Divide Hostas

“Dividing hostas is easy but can require some strength,” says Melanie.

To uproot and divide a mature clump of hosta:

1) Pry Your Hosta From The Ground

“Our main tip for division is to disinfect tools between each plant, as this is a prime opportunity for diseases to be spread,” warns Ollie.

Remembering this, use a clean garden fork or other implement to gently pry the clump up from the ground or its container.

Try to retain as much of its root system as possible and avoid dividing plants in the middle of the day, when soil is often drier.

Gently shake off excess soil so that you can see the root system more clearly.

2) Tease The Roots Apart

Carefully tease the roots apart with your hands to separate them into sections.

This is usually rather easy with a plant that has fibrous root systems like hostas.

“The natural breaks made by pulling, rather than slicing, plants apart often heal better,” advises Horticulturist Peter Lickorish.

You should not need to use a spade or other sharp implement as you will do when dividing more woody-rooted perennials (though you can use one).

However, John Plant suggests that there is no strict method for this:

“Don’t be afraid to tackle splitting with whatever it takes. This may be done by using a spade, or by simply pulling it apart.”

You may simply wish to split the clump in two, replanting one section and finding space elsewhere for the other.

Alternatively, you can opt for a slightly different method of division:

“Personally, I like to divide the plant by removing a portion of the plant from the ground, as this requires minimal disturbance of the entire plant,” says Barry Ankney.

“I like to tie back the foliage with bungee cords to open up the centre of the plant. I can then take a garden spade and cut directly down through the centre of the clump. 

“Then, using a garden fork, I dig a portion of the plant. One section then can remain in the ground, with less disturbance to its root system. 

“The portion I remove can be replanted in a new location as a clump or can be further divided into smaller clumps before relocating.”

3) Create Smaller Divisions

If you are interested in making new plants, you might separate the clump that is not to be replanted into a series of smaller divisions.

“It is often suitable to dig each clump, divide into thirds and plant only one piece back in the original hole (amended with some nice compost),” says David Teager.

“Then you have two pieces to share, making hostas live up to their nickname as the friendship plant.”

If you do this, make sure each section has some roots (as much root system as possible) and a minimum of 1-3 good buds in the above-ground portion of the plant.

4) Place Back The Parent Plant

Replant the division that will remain in place, carefully placing it back into the soil and firming the soil around it, ensuring it is planted at its original depth.

Mulch around it with organic matter.

“Some spreading (rhizomatous) hostas can simply be tidied up by digging around the edges if they get too big for their space,” says David Teager.

“Newly planted divisions could be mulched with wool pellets, which can help to deter slugs, especially early in the spring when soft new shoots are simply irresistible,” says Peter.

5) Plant Out New Divisions

Plant out or pot up the portions you have split from the parent plant as soon as possible, taking care to make sure they do not dry out.

“Hostas that are divided often take several years to recover to their mature size,” warns Barry.

Once you have replanted the parent, or settled it back in place, you can turn your attention to the new plants you have made.

You can replant hosta divisions in pots or containers, or replant them right away into another part of your garden, but make sure you choose the right sized location, says Melanie:

“Often people put large varieties in too small a container and wonder why their plant seems to get smaller every year when they simply need more root room.”

Be sure to keep your hostas well-watered, especially until they become established.

Choosing a deeper pot can help keep the large, fibrous roots keep moist and gives them better space to grow, according to Peter.

And remember that they will require more water when grown in containers, or when placed in full sun.

Siting Hostas

Remember that while some hostas can be placed in full sun, most will prefer a moist and somewhat shady site.

They can work very well in the dappled shade below fruit trees, and are an interesting edible ground cover option to think about for a fruit tree guild or forest garden.

Hostas can work well when grown in mixed planting schemes beneath an apple tree, for example.

Peter Lickorish advises contrasting their large leaves with plants with slender stems or longer, thinner foliage.

You might also grow hostas in a shady perennial border.

It can work well both in ornamental schemes and in beds or borders with other perennial vegetables and herbs.

Learning how to split hostas does not take a lot of effort.

As you can see from the above, it is an easy process, which will allow you to keep existing plants happy and healthy, and get more of these useful plants for your garden.