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Home & garden.

14 Jan 2022

How to grow irises

Irises are easy to grow and brighten up borders and pots. Discover our best iris varieties and tips on how to grow them.
CT
Ceri Thomas
Dwarf iris

Irises come in many shapes and sizes. The beautiful flowers often have delicate markings and sometimes a lovely scent, too.

Which? Gardening magazine grew a range of popular varieties to see which would give us the best display.


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Key facts

Plant type Bulbous perennial

Position Full sun

Soil Free-draining

How to grow iris: month by month

JanuaryFebruaryMarchAprilMayJune
FloweringFlowering


Flowering
Flowering
JulyAugustSeptemberOctoberNovemberDecember



Plant

Best iris varieties

Which members can log in now to see the full results and which are our Best Buy varieties. If you're not a member, join Which? to get instant access.

Best Buy dwarf irises
What it looks likeVariety nameHeight x spread
10 x 5cm
With pale sky-blue standards and a yellow streak on the darker falls, this previous Best Buy put on a superb show. It gave two weeks of peak flowering in both years, with most plants in flower at the same time. The neat, upright blooms were held well above the leaves and were untroubled by frost, wind and rain. By the second year our bulbs had multiplied, and reached their peak display a couple of weeks earlier. Peak flowering: February
What it looks likeVariety nameHeight x spread
12 x 6cm
This variety gave us three weeks of peak flowering in the first year of our trial and two in the second. Its bright blue falls, marked with a yellow streak and white speckling, were topped with paler standards with a slightly serrated edge, giving them the look of bushy eyebrows. In the second year the bulbs had clearly multiplied. They didn’t all bloom at once, but while around half were in flower, putting on a decent display, the remainder were forming buds that opened soon after and prolonged the overall flowering period. This variety flowered earlier in the second year, most likely as a result of the especially mild, wet winter. Peak flowering: February
What it looks likeVariety nameHeight x spread

How we test dwarf irises

In autumn, we bought bulbs of 18 varieties of miniature iris and planted them in shallow pots of peat-free compost, making a note of the number of bulbs planted. Each pot was covered with a layer of horticultural grit to keep weeds down and prevent the flowers being splashed with soil. The pots were positioned in a sunny, sheltered spot in the Which? Gardening magazine trial grounds. During January and February, we recorded how many bulbs emerged, the development of leaves and flowers, the impact of the blooms and the display, weather resistance and flowering duration. We also compared our flowers with pictures and descriptions to check they were the correct varieties. After flowering in the first year, the pots were given a liquid feed and the leaves allowed to die down naturally before being moved to a sunny spot where they wouldn’t be disturbed. We weeded them when necessary and waited until they began to shoot the following year so we could start assessing them again.

Caring for your plants

Planting

Plant bulbs in October in well-drained soil, positioned in full sun. If you’re planting in a pot, which is the best way to appreciate these small flowers, use a Best Buy compost for containers. Plant at a depth of twice the height of the bulb. They can be planted closely, but not touching. Cover the surface with a layer of horticultural grit to deter weeds and prevent soil splashing up and spoiling the flowers.

Pick a frost-proof terracotta container, either plain or glazed; a shallow dish shape works well for small bulbs. 

Watering

Dwarf irises are largely trouble-free and need little maintenance. Check they don’t dry out in warm weather. After your plants have flowered, give them a liquid feed and allow the leaves to die down naturally.

Common growing problems

Slugs and snails

Slugs and snails could be a problem; use slug pellets sparingly if you see signs of damage and pick off any slugs and snails you find.

Read more about slugs and snails

Squirrels

You might need to cover the pots with chicken wire to prevent squirrels and other rodents digging up the bulbs.

Read more about squirrels