If some perennial plants multiply in the garden by sowing, others are more easily propagated by dividing clumps, such as perennial geraniums. This method is the easiest, quickest and most economical way to obtain new young plants and expand flower beds. This technique also allows you to renew an old plant, exhausted after several years of cultivation or too cramped in its location. This way, you get new young plants, identical to the mother plant. Discover, in our illustrated tutorial, our advice and technique for successfully dividing a perennial in the garden.

When to divide a perennial?

Your plant should be several years old, at least 2 to 3 years, but also large enough to withstand division. Indeed, the stronger its root ball, the more its numerous roots will ensure good recovery.

The best time to divide your perennials depends on its variety. Generally, this is done after flowering, so as not to damage it and allow flowers to appear the following year. On the other hand, it is better to act during the plant's dormant period, before the resumption of growth, around early spring or late autumn. In any case, avoid periods of extreme heat, drought or frost.

Here are the most favourable times for division:

  • Perennial with spring or summer flowering: in autumn
  • Perennial with autumn or winter flowering: in spring
  • Aromatic and condiment perennial: in spring

Which plants can be divided?

Most herbaceous perennials or bulbous plants (asters, perennial geranium, campanula, iris...) can be divided, as well as ornamental grasses, aromatic plants, some perennial vegetables and a few aquatic perennials.

How to divide a perennial?

Required equipment:

Steps for dividing a perennial stump in the ground:

Before starting: Always remember to disinfect your tools to avoid transmitting diseases between your plants. Also take advantage of this division to carry out the annual pruning of your perennials, such as ornamental grasses, Asters or hostas.

1) Prepare in advance the future planting holes that will accommodate your perennials. At the bottom of the hole, mix your garden soil with potting soil, compost or well-rotted manure.

2) Carefully remove your perennial from the ground using a spade, a digging fork or a biofork. Proceed gently, preserving as much of its roots as possible.

3) Separate your clump into two, or more depending on its size. Some small perennials can be easily separated by hand, while others, more bushy and stubborn, will require cutting with a spade. You can also use shears, a knife or a small machete, but be careful with your fingers!

4) Cleanly cut damaged roots with pruners. Don't hesitate to trim unsightly or dry stems and remove faded flowers.

5) Take advantage of the fact that the root ball of your mother plant has been removed from its hole to add nutrients to your soil. Well-rotted compost, manure or potting soil will help enrich the soil again and promote vigorous recovery of your plant after this ordeal.

6) Place your root balls in the holes. The top of the root ball should be level with the ground.

7) Fill the hole with a mixture of garden soil and potting soil. Tamp gently by hand. Add some organic mulch at the base of your perennial.

8) Water generously with rainwater.

What if I want to pot my perennials?

You can also place your new young plants in pots. In this case:

1) Choose a pot with a drainage hole at the bottom.

2) Pour a layer of clay pebbles at the bottom of the pot.

3) Add some light potting soil, for example for sowing, then moisten the potting soil.

4) Place the new shoot in the pot. The top of the root ball should be 2 cm below the rim of the pot.

5) Fill the pot with potting soil, then tamp gently.

6) Water generously and place it in a saucer if necessary.

7) Place your pots in the shade and keep the substrate always moist, but without excess. Do not place your plant in full sun, as the substrate will tend to dry out too quickly, which could weaken it.

8) After a few weeks, new foliage will begin to appear. This is a sign that your perennial has recovered well. You can then plant it in the ground if you wish.

And afterwards?

  • Remember to spread an organic mulch at the base of your plants, to protect them from the cold, but also to keep them cool during the summer heatwaves.
  • As with a young plant, you will need to increase watering during heatwaves or in the absence of rain during the first year, or even the second year depending on the variety.

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