When to plant irises?
- Botanical name
- Iris germanica
- Family
- Iridaceae
Irises are planted from August to September. They flower from May to June.
Irises are perennial plants.
Irises through the year
- planting
- flowering
In short
Growing conditions
Pests and diseases
Listed here is every problem for which the sources name this plant as a host. The problems are not listed in order of how common they are.
Aphids
pest- Signs
- Colonies of small aphids sit on the shoot tips and the underside of the leaves. The leaf curls and puckers, and sticky honeydew is left on everything below. The viruses they carry are more dangerous than the feeding itself.
- Prevention
- Go easy on nitrogen, because soft sappy growth is what aphids are looking for. Encourage the predators (ladybirds, lacewings, parasitic wasps). Use a reflective mulch, which puts them off settling, and a strong jet of water to knock the colony off the tips.
Gladiolus thrips
pest- Signs
- White blotches and streaks over the leaves and flowers. In a heavy attack the petals turn brown and the buds do not open at all. On stored corms and bulbs there are rough grey brown patches.
- Prevention
- The thrips overwinters on stored corms and bulbs, so at lifting cut off the top and remove it before they dry. It is most active from July to September. In a warm room it breeds all year, so keep the store cool.
- What to do
- The source suggests putting up with light damage, seeing to a clean lifting and encouraging the natural predators. It names no insecticide.
Iris leaf spot
disease- Signs
- Brown to greyish spots with a darker edge over the leaves, spreading and running together in wet weather. The leaf dies from the tip down, while the rhizome stays sound.
- Prevention
- In autumn clear every leaf and all plant debris off the bed, because the fungi and the insects overwinter on exactly that old foliage. Plant at an airy spacing and water at the base, not over the leaves.
- What to do
- Cut the affected leaves off as they appear and take them out of the garden, not onto the compost. For the home garden the source names no product.
Iris soft rot
disease- Signs
- The rhizome softens into a mushy mass and smells foul. The fan of leaves yellows from the outside in and pulls away from the rhizome at a tug.
- Prevention
- The rhizome has to lie shallow, with its upper side at the surface and not covered by mulch, because buried and wet is what the rot needs. Remove yellow leaves as they appear, clear all foliage and debris in autumn, and keep fertiliser off the rhizome and low in nitrogen.
- What to do
- Cut the affected part of the rhizome back to healthy tissue and take it out of the garden. Clean the knife between cuts. For the home garden there is no product.
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Related plants
The plants below are in the same botanical family (Iridaceae).
Sources about the plant: ASPCA Toxic and Non-Toxic Plants, Clemson Cooperative Extension, GBIF Backbone Taxonomy, NC State Extension Plant Toolbox, Penn State Extension, University of Georgia Extension, University of Illinois Extension, Wikidata. Checked between 14 and 28 August 2026. The problem descriptions also draw on: Royal Horticultural Society, University of Wisconsin-Madison Division of Extension, Utah State University Extension.