Dividing Perennials — A Guide for the Propagation of Plants
In the realm of gardening, perennial plants are those wonderful garden inhabitants that keep on giving year after year. Perennials are the backbone of many of the most stunning gardens, with their enduring charm, structure and environmental benefits.
Dividing perennials is an easy and cost-effective method of propagation. Nature’s got an easy way of helping you grow a garden with minimal expense. Plus, it offers the perfect opportunity to swap your own garden plants with your friends, enabling you to diversify your plant collection and introduce new plants into your home garden.
But dividing perennial plants isn’t just about expanding your garden — it’s also a key strategy and common practice for maintaining the health and vitality of your perennials.
Over time, perennial plants can become overcrowded, leading to reduced flowering, stunted growth, and increased susceptibility to pests and diseases. By dividing them, you alleviate competition for resources, allowing each new plant division to thrive independently. This rejuvenation process helps your individual plants stay vigorous and blooming abundantly. It will also extend their lifespan, keeping your favourite perennials gracing your garden with their enduring beauty for years to come.
In this article, we delve into the essential and cost-saving practice of dividing and propagating perennial plants. Join us in uncovering the methods and merits of multiplying perennial plants, and discover how this simple yet effective technique can breathe new life into your garden.
How to Divide Perennials: Dividing and Propagating Perennials
Dividing herbaceous perennial plants is a common way to propagate and multiply the plants in your garden. It’s also a great way to maintain perennial health and vitality by preventing overcrowding, improving flowering, and prolonging their lifespan.
Overcrowding: Keeping Perennials Healthy with Plant Division
Perennials are known and loved for their longevity, but even the most fuss-free perennial will benefit from being lifted and separated eventually. Perennials tend to become overgrown and crowded, this can make them weak as they fight for nutrients and airflow.
If you notice a perennial plant is less floriferous (flower-producing), diseased or succumbing to pest pressure, then overcrowding could be the reason. The best time to divide a perennial is when it is looking it’s best but if you are noticing a lacklustre perennial in your garden, it is never too late to divide and revive.
When to Divide Perennials
Early spring is a great time to divide perennials as they wake up from their winter dormancy and begin to put on new growth. There is a good amount of rainfall during the spring season so the plant won’t dry out, and soil is warming which will encourage a new root system to form quickly. And the air temperature is still cool enough for the plant to put on top growth without wilting or getting scorched in the hot sun.
Dividing in spring is also ideal because the perennial will get the maximum period of growth during their growing season to establish a new root system before winter dormancy sets in again.
What is Plant Division?
Division involves separating parts of the plant that are located either at soil level or below the ground. When it comes to dividing perennials, you must firstly consider the type of stem and root system that the plant has. Each type of plant has a different growth habit that will influence the way in which you will tackle the division.
Methods of Propagation: Ways to Divide Perennials
DIVISION BY: Crown
The crown is the place on the plant where the root ball and stem join, and where new shoots will emerge. It sits at soil level and can be easily divided into pieces by lifting the clump and cutting into half or quarters with a sharp shade. Ensure each piece has both roots and new growth buds before replanting in the garden.
Examples of perennials that can be propagated by crown division include:
- Cranesbill (hardy Geranium)
- Sedum (Hylotelephium)
- Lady’s mantle (Alchemilla mollis)
- Ornamental grasses
DIVISION BY: Tuber and Tuberous Roots
A tuber is a swollen stem that is used by the plant for food storage. It is located underground and contains multiple buds per tuber.
If you wish to divide a potato tuber, you may cut it into pieces using a sharp knife. Ensure each new piece has at least one growth point (bud) before replanting into the soil.
Tuberous roots differ slightly in the way that they have a stem and buds at one end and roots at another. Buds are only formed where the previous year’s stem meets the swollen root. It is best to divide tuberous roots in the spring just as growth starts as this is when the ‘eyes’ or growth buds are most visible.
Cut them with sharp snips ensuring each section has a piece of neck and viable growth eye then leave them in a cool, dry place for a few days so that the wound heals over and there is less
chance of rotting once replanting.
Examples of perennials that can be propagated by tuber or tuberous root division include:
- Dahlia
- Daylily
- Potato
DIVISION BY: Rhizomes
A rhizome is a thick, fleshy stem that grows horizontally below the soil surface.
It can easily be divided by snapping off individual rhizomes from the clump with your hands or pruning shears if preferred. Look for rhizomes that are healthy and have strong, white roots. Discard all rhizomes that look soft or weak.
When replanting a rhizome, you may choose to cut the leaves down about to a third of their height, lay the rhizome horizontally with the shoots facing upwards and cover with no more than 5cm of soil. They will need water to help settle and produce roots however you should be careful not to overwater as they are susceptible to rot.
Examples of perennials that can be propagated by rhizomes include:
- Iris
- Persicaria amplexicaulis
- Bergenia (Bergenia cordifolia)
- Rhubarb (Rheum rhabarbarum)
DIVISION BY: Bulbs or Corms
Bulbs and corms are underground stems that function as food storage for the plants when they are in periods of dormancy. Over a season of growth, a bulb and corm will produce small offsets. When dormant, the bulbs or corm can be dug up and separated by gently pulling away the bulblets from the mother.
There are many summer flowering bulbs and corms that can be divided in spring before the new growth starts, this includes:
– Roselily (Lilium)
– Gladioli (Gladiolus)
– Drumstick allium (Allium sphaerocephalon)
DIVISION BY: Offsets
You may notice that some perennials grow baby plants at the base of the main stem. These are lateral side shoots that are called offsets or ‘pups’.
You can divide these types of perennials easily by gently tugging the offsets away from the main stem. Depending on the variety, you may not need to uplift the plant to do this. Sometimes the offset will have its own root system and sometimes it will grow one shortly after been divided from the mother plant.
Many succulents form offsets and can be propagated through this method. Other plants with offsets are:
- Echinacea (Coneflower)
- Hosta
- Achillea millefolium (yarrows)
DIVISION BY: Runners
Some perennials will send out something called a ‘runner’. This is a horizontal stem that is produced by the parent plant. It can creep along the surface of the soil or underneath it to form new roots and shoots until a young plant is grown.
To divide plants with runners, simply lift the young plant, including its roots and separate it from the mother by cutting the horizontal stem. You can replant in a separate area of the garden.
Some examples of plants that can be divided by runners include:
- Bog sage (Salvia uliginosa)
- Goldenrod (Solidago)
- Apple mint (Mentha suaveolens)
- Strawberries
- Japanese anemone
DIVISION BY: Suckers
A sucker is a basal shoot that grows upwards from the main plant’s root system. Suckers can be very vigorous and sometimes appear a distance away from the parent plant.
To divide and propagate using suckers firstly you must loosen the soil with a garden fork. Gently lift the sucker and along with the roots and make a cut with a sharp knife to detach from the mother.
It is important to note that suckers on a grafted tree or shrub should not be used to propagate. These suckers come from the rootstock and will not reproduce the known cultivar.
Perennials that can be divided by suckers include:
- Raspberry
- Lilac
- Rose
Plant Propagation: Step-by-Step Instructions
A step-by-step tutorial for perennial plant propagation by division:
- Take a sharp spade or garden fork and dig up the the whole plant. Allow a 20 cm perimeter around the plant to avoid the risk of root injury. You may need to cut back any dead or woody plant stems first to clear the area and allow better visibility.
- Once free, gently lift the plant and shake off any excess soil from around the roots.
- Divide the perennial using one of the following methods:
a. Use a sharp spade to separate the crown.
b. For tubers, divide into pieces with sharp snips.
c. Rhizomes, bulbs and corms can be gently broken up with your hands or an old knife.
d. Offsets can be teased apart using your hands.
e. Suckers and runners can be cut using scissors or snips. - To ensure success, allow at least three growth points and a set of healthy roots per division.
- Trim off any dead or diseased parts of the plant.
- Replant into the garden immediately, spacing out the division with adequate room to grow on and at the same depth as it originally grew. (Digging new planting holes before uplifting the plant for division is a good idea.)
- Water in well and frequently over the next week or so until it establishes.
AFTER CARE: Planting plant divisions
After you lift a perennial, it’s important to replant the division as quickly as possible. Work some compost into the soil before replanting. If an area of the garden is not yet ready to plant into, then you can wrap in newspaper or pot up the division in fresh potting soil. Keep it moist and in a shaded area until transfer into the garden is possible.
You may choose to soak the division in a bucket of seaweed tonic for 20 minutes prior to planting to give it a boost and help with transplant shock.
You may notice in the days following transplant, the top growth can appear limp and wilted. Don’t be alarmed as this is the plant’s normal reaction to root disruption. Wilting is caused by transpiration, and until the roots establish, more water is being lost than coming in. Take care during this period not to let the division dry out, keep it well watered until the new plant settles.
Perennials like to be divided at least every three to four years, they often respond with rapid growth and increased vigour. If you are noticing smaller than usual flowers or a plant that has died in the middle, then it is time to divide and revive.
Get dividing this spring and you will be rewarded with healthy perennials that bloom in the garden all summer long!
