Dividing Perennials To Make New Plants

Propagating plants at home is something that all gardeners should consider. Propagating plants is not only about growing new plants from seeds. It is also about using other methods to increase plant stocks in your garden. In this article, we will discuss dividing perennials to make new plants. This is one of the very easiest ways to propagate perennial plants. It is something that any gardener can easily learn how to do.

What Does ‘Dividing Perennials’ Mean?

When we talk about ‘dividing perennials’ we are just talking about the process of separating a mature perennial plant to create two or more plants. It is as simple as that. Usually, this is a case of dividing the root ball or root system by hand, or with a garden spade.

Why Divide Perennials?

You may divide perennials simply to produce new plants to place elsewhere in your garden, to give away to friends or family, or even to sell. But another reason to divide perennials is to keep your garden healthy and productive. Perennial plants will often spread as they mature. These spreading perennials can become overcrowded over time, and their health and vigour can suffer. Dividing these plants and thinning out the growing area can help to keep them in tip top condition.

When Should You Be Dividing Perennials?

As long as moisture levels are maintained, many perennials can be successfully divided at almost any time. However, the best time to divide plants is during the dormant period in winter, when they are not in active growth. Summer-flowering plants are best divided in early spring or autumn. If the autumn is a particularly wet one, it is a good idea to delay division until the spring. Waiting until the spring may also be a better choice for plants that are on the tender side.

One of the exceptions to this general advice are spring flowering plants like irises. These are best divided in the summer (June-August) after flowering. This is because this is the period during which these plants will be focussed on root growth.

Which Perennials are Suitable for Division?

Generally, any perennials that throw up more than one stem from a crown, or root ball, will be suitable for division. These clump-forming herbaceous perennials can be split into two or more sections which retain some root system. Examples of the perennials that can be suitable for this gardening practice include:

• Anemone
• Aster
• Bergenia
• Comfrey
• Convallaria
• Crocosmia
• Delphinium
• Euphorbia
• Geranium
• Helianthus
• Hemerocallis
• Hosta
• Iris
• Ornamental grasses
• Primula
• Ranunculus
• Salvia
• Sedum
• Verbena
• Zantedeschia

When thinking about division, you may also wish to consider separating suckers, plantlets or runners from the parent plant. A number of different perennial plants, including fruit canes like raspberries and blackberries, and strawberries, are suitable for this treatment. The ajuga (bugle) is one example of a plant that produces small individual plantlets around the parent plant that can also be divided from it and planted elsewhere.

Methods for Dividing Perennials

While this is an extremely simply gardening practice, it is important to understand that there are several different ways to go about dividing perennial plants. The method that you choose will depend on the type of plant you are dealing with, and what sort of root system it has.

Dividing Perennials With Smaller, Fibrous Roots

If the perennial that you have to divide has smaller, fibrous roots, this first method can be used for division:

• Begin by cutting into the ground around your plant to loosen the root system, trying to retain as much of the root system as possible.
• Lift/ease the plant gently from the ground, taking care to keep the roots as intact as possible.
• Shake excess soil from the roots, so that you can see their structure more clearly.
• Take note of sections that can be divided, while retaining some roots and some above ground growth.
• Gently pull the root system apart with your hands in order to create these sections.
• Replant your divisions in containers or elsewhere in the ground as quickly as possible. Then be sure to water them in well. Try to reduce stress upon transplantation by taking care to provide conditions that are as similar to the original growing position as possible.

Dividing Perennials With Thicker Roots and Crowns

For fibrous-rooted perennials with larger root sections (like Day Lily or Hemerocallis, for example) you might need to use tools to separate your divisions. Where the crown can not be pulled apart by hand, you can often pry the plant apart using two garden forks, back to back, and applying pressure to pull the sections away from one another. 

In certain cases, you may even need a sharp knife or cleaving tool to divide the clump. Woody crowned plants (like Helleborus) or fleshy rooted plants (like Delphinium) will usually need to be cut with a sharp knife or a garden spade, depending on the size and maturity of the plant. 

However you divide the clump, you should aim to create new plants which have at least 3-5 healthy shoots and as much root system as possible. The more roots remain on each new plant, the quicker the plants will be to reestablish themselves once replanted. The larger the sections that you form, the easier it will be for these to become reestablished elsewhere in your garden.

Dividing Perennials Without Uprooting the Whole Parent Plant

This method is suitable for many larger and more established perennial clump-forming perennials. Comfrey is one good example to illustrate this method of division. With just one division of this useful plant, it is possible to obtain a number of crown offsets and root offsets, which can be used to make plenty more plants. 

Rather than lifting the whole plant, in this case, you will simply take divisions from the edges of the parent plant. This means that the parent plant will usually be relatively unaffected and its growth will generally be able to continue unchecked. 

• Select a strong, healthy, mature plant.
• Identify a section on the edge of the clump to remove from the parent. Clear the area around it so you can more easily see what you are dealing with.
• Cut straight downwards into the ground with a spade to separate this section from the clump.
• Ease the divided section of the plant from the ground and put it to one side.
• Refill the hole that has been made with soil/compost and firm it back down gently around the parent plant.
• Shake, brush or rinse excess soil from the roots of the division so you can see what you have to work with more clearly.
• Cut off any large leaves that remain on the tops of the plant. 
• If you wish, you can simply replant this division right away.

Creating Crown and Root Offsets from Divisions

However, with comfrey and other such plants, you can also choose to make further divisions of the section that you have removed from the parent plant. Using your fingers or a sharp knife, divide the crown to create crown offsets. Leave a few centimetres of root on these crown sections. 

If you wish, you can remove longer root sections and cut these into root offcuts that can also be used to make new plants. Root offcuts should be around 5cm in length. Crown offsets which have both root and growing tip will get going more quickly in spring, but root offsets, while they do so more slowly, can also effectively grow into new plants. 

Dividing Plantlets, Suckers or Runners From the Parent Plants

Plantlets and suckers that have taken root close to parent plants can often simply be carefully dug up (retaining as much of the root system as possible) and replanted elsewhere in the garden. Runners (such as those on a strawberry plant, for example), can be guided to take root in the soil of your patch, or positioned to root into containers that will allow them to take root, and later be cut away from the parent plant. 

Dividing perennial plants will help you to continue to fill gaps in growing areas and to enhance your garden over the years. Divisions will always grow into plants that are identical to the parent plant, so this is an extremely reliable means of propagation. Of course, dividing perennial plants that have become too large can help to reduce overcrowding and keep plants healthy too. 

Do you divide perennials in your garden? Share your tips, tricks and suggestions in the comments below.