Divide perennials – and get more plants for free
In spring and autumn, you can divide perennial plants that have become too large. The plants will thrive better, and you'll get new young plants that look exactly like the parent plant. Here’s how to effectively divide plants.
When perennials (flowering plants) have grown large and start to become thin in the center, it’s time to divide them. This is mainly because nutrients and water can no longer reach all the root threads, but also to get more plants!
Most plants don’t need to be divided more often than every five years, but some perennials, such as rock garden plants, can be divided more often—about every three years. Some plants take extra long to develop and should only be divided about every ten years; examples include umbrella plant, peonies, ash tree roots, hostas, large help, daylilies, astilbe, gillenia, and bishop's hat.
Which perennials cannot be divided?
Plants with a taproot should not be divided; instead, they can be propagated from seeds. This applies to plants such as columbine, mullein, oriental poppy, and bridal veil. Taproot plants are easy to recognize in spring when they form a single rosette of leaves above the soil surface—they only have one growth point.
When is the best time to divide perennials?
A general rule of thumb is that plants that bloom in the spring should ideally be divided in the fall, while plants that bloom in late summer and fall should be divided in the spring.
Examples of plants that should be divided in the fall
- Myosotis
- Rock cress
- Silverweed
- Bishop's hat
- Spring spurge
- Tiarella 'Sugar and Spice'
- Virginia creeper
- Spring violet
- Globe flower
- Catnip
- Yarrow
- Geranium
- Daylily
- Siberian iris
Examples of plants that should be divided in the spring
- Astilbe
- Autumn phlox
- Autumn asters
- Crown jewel
- Autumn anemone
- Chrysanthemum
- Helenium
- Hosta (plantain lily)
- Japanese anemone
- Goldenrod
- Coneflower
- Monkshood
- Garden buttercup
- Great masterwort
How to divide perennials – step by step
- Water the plant and soil thoroughly, preferably the day before.
- Dig up the entire plant and root system, trying to get as much of the roots as possible.
- Divide the root ball with a sharp spade or knife, as this creates clean wound edges and reduces the risk of diseases. Make sure each division has new shoots/growth points. If the center of the clump looks thinner, divide it there to minimize damage to the roots and shoots. Depending on the size of the root, you can divide the plant into more than two sections.
- Keep the divided plants moist and replant them as soon as possible. Choose a location for the transplant where the plant gets what it needs in terms of soil, water, and sunlight. Don’t plant too closely together, as it may take a couple of seasons for the new plants to grow large, but they will need more space over time. If the area around the plants looks empty, you can temporarily fill the gap with annual summer flowers.
- Remove any weeds that may steal energy from the new plants.
- Remember to water thoroughly at the beginning, as newly divided roots have a slightly reduced ability to absorb water.
A true copy
By digging up and dividing large plants, you get exact copies of the parent plant, which isn’t always the case with seeds. This can be useful if, for example, you want to maintain a specific color in the bed or have a favorite flower.
Take the opportunity to give away small plants when dividing, this way you not only spread joy but also important flowers for pollinators, such as bees and butterflies.
Propagate plants with cuttings
You can also create more plants through vegetative propagation, which means propagating the plants using plant parts, such as pieces of a stem, stalk, leaves, or roots. These can be planted or grafted, depending on the variety.
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