Repotting guide

When & how to repot Iris (Iris germanica)

Also called bearded iris, German iris, flag iris.

About Iris

Iris germanica · also called bearded iris, German iris · flowering

Bearded iris is a rhizomatous perennial grown for showy late-spring flowers in every colour. Plant rhizomes with the tops at soil level in full sun. Divide every 3-4 years. Toxic to pets — rhizomes are the most dangerous part.

Iris is a large Northern Hemisphere genus split into two structural groups: rhizomatous types (bearded/German, Siberian) that grow from thick surface rhizomes, and bulbous types (Dutch, reticulata) that grow from true bulbs — a distinction that drives all planting and care decisions.

Plant bearded rhizomes horizontally with the top one-third to one-half exposed at the soil surface; plant bulbous iris in fall about 3 in deep, like small daffodils.

Mature size: 60-100 cm tall in flower

Watch for — Soft rotting rhizomes: Iris borer or wet rot; dig and discard, replant in dry sunny spot.

Sources: missouribotanicalgarden.org, aspca.org, rhs.org.uk

How to tell iris needs repotting

Repotting on a calendar is less reliable than reading the plant. For iris, watch for these signs:

Flowering has tailed off year on year and the clump has become congested and overcrowded.
Lots of leaf and few flowers — a classic sign that iris bulbs or tubers need lifting and dividing.
Bulbs visibly bursting the pot or pushing each other to the surface.
It is the natural dormancy window (foliage yellowed and died back) — the only safe time to lift and split.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot iris

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, iris is lifted and divided once the clump congests and flowering drops off. Rhizomatous perennial.

What size pot to step iris up to

Pot size matters less than depth and spacing here. When you replant iris, set the bulbs or tubers at the correct depth (a rough guide: two to three times their own height of soil over the top) and space them so they are not touching. A wide, shallow pot suits a clump better than a tall narrow one.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot iris

The only safe window is dormancy: wait until the foliage has yellowed and died back naturally, lift and divide then, and replant before or at the start of the next growing season. Disturbing iris in full growth or flower sets it back badly.

Step-by-step: repotting iris

Wait for dormancy. Let iris foliage yellow and die back completely. Lifting while it is in growth wastes the energy it is storing for next year.
Lift carefully. Loosen the soil well away from the bulbs/tubers with a fork and ease the whole clump out without spearing them.
Separate the offsets. Gently pull the clump apart into individual bulbs or tubers. Keep only firm, healthy, blemish-free ones.
Replant at the right depth. Reset them in fresh free-draining alkaline loam at the correct depth and spacing — not touching — so each has room to bulk up.
Water in and rest. Water once to settle them, then keep on the dry side until growth resumes. Do not feed until leaves are actively growing.

Aftercare

After replanting iris, keep the soil barely moist — not wet — until shoots appear; bulbs and tubers rot in cold, saturated soil. Once leaves are growing strongly, resume normal watering. Hold off feeding until the plant is in active growth again.

The right soil mix for iris

Iris wants free-draining alkaline loam. pH 6.5-7.5; hates wet feet. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting iris — frequently asked questions

How often should you repot iris?

Lift and divide every 3–4 years once clumps congest for iris. Iris is lifted and divided, not "repotted". Every 3–4 years, once the foliage has died back and it is dormant, lift the clump, separate the offsets, and replant at the correct depth in free-draining alkaline loam. Crowding, not pot size, is what reduces flowering over time.

What size pot does iris need?

When is the best time of year to repot iris?

Do you "repot" iris, or lift and divide it?

You lift and divide it. Iris grows from bulbs or tubers, so instead of repotting you wait for dormancy, lift the congested clump, separate the healthy offsets, and replant them at the right depth and spacing. Doing this every 3–4 years restores flowering.

Should you fertilise iris after repotting?

Hold off feeding iris until it is in active growth again. Fresh soil already carries enough nutrients to get it re-established, and feeding disturbed roots too soon does more harm than good.