Bearded iris
Four irises with four sets of rules. Bearded irises grow from a rhizome that must bake in the sun at the soil surface; water-loving ones (sibirica, ensata, pseudacorus) want the opposite, a damp or boggy spot; reticulata are small early bulbs for pots and gravel; dutch irises are cut-flower bulbs.
The single commonest mistake is burying a bearded iris rhizome or mulching over it. Covered, it does not flower and eventually rots — it needs its back in the sun the way a lizard does.
Bearded
Bearded
Plant with the rhizome top exposed and facing the sun — burying it too deep is the most common first-year mistake.
Care
Essential; the rhizome genuinely needs to 'bake' to flower well.
Drought-tolerant once established.
Free-draining, neutral to alkaline soil; the rhizome must sit proud on the soil surface, never buried.
Trim foliage into a fan shape after flowering if tidying; divide congested clumps every 3-4 years.
A low-nitrogen feed — bone meal or a rose fertiliser — as growth starts, and again after flowering. Never mulch or feed over the rhizome itself: it needs to bake in the sun, and anything piled on it invites rot.
Lift and divide about six weeks after flowering: cut the rhizome into pieces each with one fan of leaves and healthy roots, trim the leaves back by half, and replant with the top of the rhizome above the soil.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- MarchLight feed, low in nitrogen — too much reduces flowering and encourages rot. how ›
- MayDeadhead spent flower spikes. how ›
- JulyDivide congested clumps after flowering, replanting with rhizome tops exposed to the sun. how ›
Months based on climate: UK. Your choice stays on this device.
- MarchLight feed, low in nitrogen — too much reduces flowering and encourages rot. how ›
- MayDeadhead spent flower spikes. how ›
- JulyDivide congested clumps after flowering, replanting with rhizome tops exposed to the sun. how ›
Months based on climate: Northern Italy. Your choice stays on this device.
- FebruaryLight feed, low in nitrogen — too much reduces flowering and encourages rot. how ›
- AprilDeadhead spent flower spikes. how ›
- JulyDivide congested clumps after flowering, replanting with rhizome tops exposed to the sun. how ›
Months based on climate: Central Italy. Your choice stays on this device.
- FebruaryLight feed, low in nitrogen — too much reduces flowering and encourages rot. how ›
- AprilDeadhead spent flower spikes. how ›
- JulyDivide congested clumps after flowering, replanting with rhizome tops exposed to the sun. how ›
Months based on climate: Southern Italy and islands. Your choice stays on this device.
Common problems
How to spot it. Soft, foul-smelling rhizome.
What to do. Lift, cut out the rot, replant shallow.
How to spot it. Caterpillar-like larvae stripping leaves.
What to do. Remove by hand.
How to spot it. Brown spots in wet weather.
What to do. Remove affected leaves.
Siberian irisJapanese iris
Siberian iris
Keep consistently moist from planting; never let this group dry out the way a bearded iris can tolerate.
Care
Standard for this group.
Genuinely wants consistently moist to boggy soil, ideal at a pond margin.
Moisture-retentive to boggy soil; tolerates shallow water for part of the year. Ensata dislikes lime and standing water in winter more than sibirica does — worth noting when choosing between the two.
Cut back dead foliage in late autumn, or leave over winter for structure and cut back in early spring instead.
One balanced feed as growth begins is plenty; in a pond basket use only an aquatic-specific slow-release feed, since ordinary fertiliser leaching into the water triggers algae.
Divide established clumps after flowering, cutting through the rhizome mass with a spade and replanting vigorous outer pieces. The tired centre of an old clump is worth discarding rather than replanting.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- MarchCut back last year's dead foliage before new growth starts. how ›
- AprilFeed as growth resumes, especially in pond-margin planting baskets. how ›
- OctoberDivide congested clumps. how ›
Months based on climate: UK. Your choice stays on this device.
- MarchCut back last year's dead foliage before new growth starts. how ›
- AprilFeed as growth resumes, especially in pond-margin planting baskets. how ›
- OctoberDivide congested clumps. how ›
Months based on climate: Northern Italy. Your choice stays on this device.
Common problems
How to spot it. Larvae stripping leaves.
What to do. Remove by hand.
How to spot it. Browning, stunted growth if soil dries.
What to do. Keep consistently wet, unlike bearded iris.
Iris reticulataDwarf iris
Iris reticulata
Plant in autumn at a shallow depth; can flower as early as January in a sheltered spot.
Care
Full sun.
Standard bulb watering.
Free-draining; shallow planting depth suits a pot or trough as well as open ground.
Not applicable — deadhead and leave foliage to die back naturally.
Feed with a high-potash fertiliser while the leaves are still green after flowering — these bulbs often flower brilliantly the first year and then split into non-flowering offsets, and feeding is what limits that.
Lift the clump when dormant in summer and separate the small offsets; grown on in a gritty, well-drained spot they reach flowering size in a couple of years.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- FebruaryDeadhead as flowers fade. how ›
- AprilLeave foliage to die back fully before removing.
- OctoberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: UK. Your choice stays on this device.
- FebruaryDeadhead as flowers fade. how ›
- AprilLeave foliage to die back fully before removing.
- OctoberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Northern Italy. Your choice stays on this device.
- JanuaryDeadhead as flowers fade. how ›
- MarchLeave foliage to die back fully before removing.
- OctoberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Central Italy. Your choice stays on this device.
- JanuaryDeadhead as flowers fade. how ›
- MarchLeave foliage to die back fully before removing.
- NovemberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Southern Italy and islands. Your choice stays on this device.
Common problems
How to spot it. In waterlogged soil.
What to do. Improve drainage.
How to spot it. On young shoots.
What to do. Protect emerging growth.
How to spot it. Occasionally affecting stored bulbs.
What to do. Check stored bulbs periodically.
Dutch iris
Dutch iris
Plant in autumn at typical bulb depth; taller and later-flowering than reticulata types, and a good source of cut flowers.
Care
Full sun.
Standard bulb watering.
Free-draining; typical bulb planting depth and conditions.
Not applicable — deadhead and leave foliage to die back naturally.
A high-potash feed from flowering until the leaves yellow builds the bulb for next year. On heavy, damp soil these are often treated as a one-season bulb, in which case skip it.
Lift when dormant and detach the offsets from the base of each bulb. Replant the largest immediately and grow the small ones on for a year or two.
Month by month
Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.
- MayDeadhead as flowers fade. how ›
- JulyLeave foliage to die back fully before removing.
- NovemberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: UK. Your choice stays on this device.
- MayDeadhead as flowers fade. how ›
- JulyLeave foliage to die back fully before removing.
- NovemberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Northern Italy. Your choice stays on this device.
- AprilDeadhead as flowers fade. how ›
- JulyLeave foliage to die back fully before removing.
- NovemberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Central Italy. Your choice stays on this device.
- AprilDeadhead as flowers fade. how ›
- JulyLeave foliage to die back fully before removing.
- DecemberPlant bulbs this month, alongside other autumn bulbs.
Months based on climate: Southern Italy and islands. Your choice stays on this device.
Common problems
How to spot it. In waterlogged soil.
What to do. Improve drainage.
How to spot it. On young shoots.
What to do. Protect emerging growth.
How to spot it. Occasionally affecting stored bulbs.
What to do. Check stored bulbs periodically.
Popular varieties
Questions
Bearded iris: is it hardy?
Bearded: H6: Hardy in the vast majority of UK gardens. It survives down to −20 °C. Siberian iris: H7: Fully hardy anywhere in the UK. It survives below −20 °C. Iris reticulata: H7: Fully hardy anywhere in the UK. It survives below −20 °C. Dutch iris: H5: Hardy in most of the UK, but can struggle in the coldest inland or upland spots. It survives down to −15 °C.
Can it grow in a pot?
Bearded: Shallow, wide pot with very free-draining compost. Siberian iris: Ideal in a planting basket for pond margins. Iris reticulata: One of the best bulbs for a very early spring pot or trough display by the front door. Dutch iris: Grows well in a pot, though more commonly used in a border or cutting garden.
Bearded iris: when do you prune it?
Bearded: Trim foliage into a fan shape after flowering if tidying; divide congested clumps every 3-4 years. Siberian iris: Cut back dead foliage in late autumn, or leave over winter for structure and cut back in early spring instead. Iris reticulata: Not applicable — deadhead and leave foliage to die back naturally. Dutch iris: Not applicable — deadhead and leave foliage to die back naturally.
Bearded iris: when does it flower?
Bearded: In the climate of UK it flowers in May–June. Siberian iris: In the climate of UK it flowers in June–July. Iris reticulata: In the climate of UK it flowers in January–March. Dutch iris: In the climate of UK it flowers in May–June.
When do you feed it?
Bearded: A low-nitrogen feed — bone meal or a rose fertiliser — as growth starts, and again after flowering. Never mulch or feed over the rhizome itself: it needs to bake in the sun, and anything piled on it invites rot. Feeding months, UK: March, July. Siberian iris: One balanced feed as growth begins is plenty; in a pond basket use only an aquatic-specific slow-release feed, since ordinary fertiliser leaching into the water triggers algae. Feeding months, UK: April. Iris reticulata: Feed with a high-potash fertiliser while the leaves are still green after flowering — these bulbs often flower brilliantly the first year and then split into non-flowering offsets, and feeding is what limits that. Feeding months, UK: March–April. Dutch iris: A high-potash feed from flowering until the leaves yellow builds the bulb for next year. On heavy, damp soil these are often treated as a one-season bulb, in which case skip it. Feeding months, UK: April–May.