Optimum Planting Time: September – November
Flowers: February - March
Height: Up to 90cm for taller varieties, 10-15cm for dwarf varieties
Where to plant
Plant your iris rhizomes where the soil drains well and in full sun. There are two main type of irises -
the most well-known border iris is Iris germanica, sometimes known as bearded iris, as well as the
miniature iris varieties Iris histrioides and Iris reticulata.
How to plant in the ground
1. Dig a hole, large enough for the rhizome and roots.
2. If planting in heavy soil, mix in a bulb compost with added grit to add drainage in borders or
3. Plant 10cm in depth and 30cm apart, these look best when planted in groups.
4. If you mound the soil slightly in the centre of the hole, it can make placing the rhizomes
easier. Work the soil back between the roots so they’re covered but leave the top of the
rhizome exposed to the sun, to ensure flowering for next year.
5. Water in well after planting.
How to plant dwarf iris in containers
1. Use a mix of two parts bulb or potting compost and one part grit for sharp drainage
2. Space the bulbs over the surface so they don’t touch, approximately 7cm deep and 10cm
3. Cover the rhizomes with 5cm of compost and firm in lightly, then water.
4. Leave the top of the rhizome exposed to the sun to encourage flowering.
- Feed irises once every two weeks during watering using a low nitrogen fertiliser such as
- A decrease in blooms usually indicates that it’s time to divide, so consider dividing your iris
every few years. This is necessary, particularly for container irises because it keeps the plant
from overcrowding or suffocating itself.
- Cut back the foliage to a third before digging up the clumps.
- Separate healthy new rhizomes from the older ones toward the centre of the clump. Discard
any rhizomes with holes or disease.
Pests and Diseases
Irises can be prone to fungal diseases such as leaf spot (Cladosporium iridis), ink disease (Bipolaris
iridis), rust (Puccinia iridis) and rot (Pectobacterium carotovorum). To prevent these, it’s
recommended all leaf debris at the end of each year and plants affected by ink disease are best
disposed of. Plant rhizomes in well-drained soils to avoid bacterial rot. Fungicides with
tebuconazole and trifloxstrobin also carry a recommendation for use against leaf spots on
ornamentals plants and may have some effect against iris leaf spot or ink disease.