How to Divide Overgrown Perennials

Three Parts:Deciding When to Divide PerennialsDividing Perennial RootsUsing Alternative Division Methods

Perennials are plants that live for longer than two years. Despite their relatively long-lives, perennial plants can appear lackluster after several years of growth. Dividing these plants is a good way to refresh them. It’s also good way to control the size of some spreading plants, or even to multiply them. Common garden perennials include foxglove, peony, hosta, carnation, iris and many herbs and ornamental grasses.

Part 1
Deciding When to Divide Perennials

  1. Image titled Divide Overgrown Perennials Step 1
    Divide perennials every three to five years. Many perennials will benefit from being divided every three to five years or so. One sign that your perennial plant is in need of division is a bare patch in the center of the plant. This indicates the plant is dead in the center of its root mass, but has fresh growth around the edges of it.
  2. Image titled Divide Overgrown Perennials Step 2
    Separate the plants in the fall or spring, when they are dormant. The best time to divide perennials is the fall or spring, or whenever the plants are dormant. For example, perennials which flower in spring or in summer are best divided after they bloom — in late summer or early fall. Those that bloom in the fall can be divided in spring. Peonies in particular prefer to be divided in the fall.
    • However, plants can be divided at any time of the year provided they aren’t allowed to dry out afterwards. Too little watering is the most common reason for plants to fail.
  3. Image titled Divide Overgrown Perennials Step 3
    Consider dividing the perennials once new shoots emerge. Some gardeners prefer to divide their plants in spring, when the new shoots emerge. This is because the fresh growth is a good indication of which are the healthier parts of the plant. Parts which do not produce fresh shoots can be discarded when the plant is divided.
  4. Image titled Divide Overgrown Perennials Step 4
    Choose a cool or cloudy day to avoid drying the roots. Division exposes the roots of the plant to the air. It is best to divide perennial plants in cooler temperatures and on cloudy rather than sunny days, as this will prevent the roots from becoming too dried out while they are above ground.

Part 2
Dividing Perennial Roots

  1. Image titled Divide Overgrown Perennials Step 5
    Prepare the soil at the plants' new location. Start by preparing the soil in the new location for your divided new plants. In most cases it will be sufficient to incorporate some compost or well-rotten manure into the new planting spots.
  2. Image titled Divide Overgrown Perennials Step 6
    Give your plants a good watering the day day before you divide it. The day before you divide your plants, give them a good water. This ensures the plants are well hydrated before you begin.
    • Being short of water is a source of stress to perennial plants and division is only going to stress them further. This is why it’s best to make it easier on the plants by ensuring they are well hydrated.
    • You might like to trim the plants above ground if this will make it easier to handle when dividing.
  3. Image titled Divide Overgrown Perennials Step 7
    Carefully dig out the root mass of the plant you are dividing. Observe the depth to which the plant is located in the ground, as you will need to replant the separated root sections to the same depth in the new location later.
    • Try to keep as much root intact as possible and avoid damaging the roots. Gently shake or hose off excess soil.
    • Remove any dead, damaged or diseased roots and stems. If the plant roots are mushy or show signs of rot, try to cut this away to leave any healthy root.
  4. Image titled Divide Overgrown Perennials Step 8
    Choose a division method based on the type of plant. With some plants, it may be possible to gently pull apart the root mass with your fingers. This method is suitable for fibrous rooted plants or ones not joined at the crown such as bulbs or rhizomes. These include hostas and day lilies.
    • Plants such as bearded iris will be made up of joined rhizomes - a knife is required to separate these.
    • With tough or woody root masses you may need to insert two garden forks to prize it apart, or cut it with a spade or knife.
    • Some very tough and woody perennials may require an ax or saw.
  5. Image titled Divide Overgrown Perennials Step 9
    Make sure each new plant section has three to five healthy shoots. Generally it’s best to divide the perennial so each new section of plant has between three and five healthy shoots. Some larger plants may require division into many sections. Other plants may only need to be halved or quartered.
  6. Image titled Divide Overgrown Perennials Step 10
    Replant the divided perennials immediately. You should plant the divided parts immediately, to the same depth as the original plant. Either replant outdoors straight away, or plant into pots to nurture in a greenhouse or indoors until the new young plants are established.
    • You should keep the new plants watered until they are established. The best way is to water every two or three days for the first few months.
      Image titled Divide Overgrown Perennials Step 10Bullet1
    • Many perennials don’t flower their first year so be prepared to wait longer for newly divided plants to bloom.
  7. Image titled Divide Overgrown Perennials Step 11
    Add some compost to the soil if you are replanting in the original location. If you are replanting one divided plant back into the original location, remember that the local soil will probably benefit from some improvement.
    • The presence of the plant over the last few years will have taken some of the nutrients from the soil.
    • Therefore, you might like to dig in some compost or well-rotted manure before you replant in that same spot.

Part 3
Using Alternative Division Methods

  1. Image titled Divide Overgrown Perennials Step 12
    Divide perennial bulbs. After several years, perennial bulbs may form smaller ‘bulblets’ or ‘corms’ around the original bulb. In terms of appearance, this is not unlike a head of garlic with the separate cloves within. In plants such as daffodils this can eventually cause perennials to become overcrowded and impair the flowering. That’s a sign that it’s time to divide the corms from the parent bulb.
    • Wait until the above-ground foliage has withered away. In most cases this will be in the fall. Dig up the bulb and gently separate the corms using your fingers. Discard smaller ones or any affected by damage, disease or mushy with rot.
    • It’s best to replant these separated bulbs immediately, but if you can’t you should store them as for overwintered bulbs — in a paper bag in a cool, dark and dry place.
  2. Image titled Divide Overgrown Perennials Step 13
    Separate perennial plants with the need for digging. A small number of perennials can be divided without needing to dig the original plant up. It’s better if you can avoid digging the entire plant up, as this places it under immense stress.
    • Instead, you can cut root sections from the side edges of perennials such as geranium or Jacob’s ladder and replant them, without needing to remove the entire root mass.

Article Info

Categories: Home and Garden