The Ultimate Guide to Growing Iris Flowers

Irises are gorgeous flowers and a great addition to any outdoor garden. The iris family is enormous, but most people grow just a few of the most common domestic irises.

These gorgeous flowers come in a variety of colors – that’s probably why they’re named after the Greek goddess of rainbows. These perennial flowers will come back as showy displays every year, making them a favorite of gardeners.

Many irises prefer wetter soil, but there’s a wide variety of conditions in which they grow best. Of course, one of the first steps to proper iris care is understanding which species or breed of iris you have! Understanding the needs of your plant and how those needs interact with your local climate is absolutely imperative.

Common species of garden iris include:

• Bearded iris. This species is very popular, and as such there are several sub-varieties. Bearded irises love having their personal space and don’t require mulch. These gorgeous flowers come in any color except for fire-engine red. These irises are tall (often 28 inches or so) and have slightly hairy petals – thus the “bearded” moniker.
• Dutch iris. This iris grows readily from bulbs spaced just 3 inches apart or so. They’re gorgeous cut flowers that love growing in sunny locations.
• Iris laevigata. These flowers grow well along the edges of ponds but aren’t quite as tough as the pseudacorus below.
• Iris pseudacorus. This yellow iris is so tough that it’s not often grown in gardens. It readily survives on its own in semi-wild, wet areas.
• Iris reticulata. These delicate flowers grow best in well-drained and sunny soil. Their blooms are generally purple or purplish blue.
• Siberian iris. This species of iris needs to grow in wet areas when it’s young but can survive in drier areas as it matures.

There are over 300 different iris species within the genus. As such, it’s difficult to give you an exact how-to guide for iris flowers. Each species will do better in slightly different environments from the next.

Where You Can Grow Irises

The best way to ensure that you’re growing your plants in the correct climate, be sure that you know what USDA Plant Hardiness Zone you live in. If you’re outside of the United States, check out the Hardiness Zone Map of Europe, Asia, Africa, Oceana, or Central and South America.

• Bearded Irises grow well in zones 3 to 9
• Dutch Irises grow well in zones 5 to 9
• Iris laevigata grows well in zones 5 to 9
• Iris pseudacorus grows well in zones 5 to 8
• Iris reticulata grows well in zones 4 to 9
• Siberian Irises grow well in zones 3 to 9

If you’re planning on growing a different species or other variety of iris, just make sure that you’ve double-checked its hardiness zone compared to where you live!

13 Tips to Growing Your First Bearded Irises

We’ll mostly focus on bearded irises here because those are the most common iris species. While these tips may be true for other iris species, it’s important to double-check the needs of your species!

1. Most irises prefer at least a half day of sun. Some species will wither even with light shade.
2. Bearded irises prefer well-drained soil.
3. Fertile soil is generally best; it should be slightly acidic. You can use a bit of lime to add to the acidity of your soil if needed.
4. Iris bulbs or rhizomes should be planted in mid-summer to early fall.
5. Bearded irises need about 1 to 2 feet apart. They’re generally either planted alone or in trios.
6. Bearded irises should be thoroughly watered.
7. Some fertilizer is good, but too much can lead to rhizome rot.
8. Bearded irises have rhizomes, which should be exposed or lightly covered in hot climates. Bulbs, in contrast, thrive deep underground.
9. Don’t trim back the leaves after the flowers have died off. You can trim brown tips and cut the flower stalk to the root, but don’t remove the green leaves!
10. Heavy frost can lead to borer eggs that may kill your iris.
11. After a few years, you may need to divide and replant your rhizomes just after they finish blooming. Cut the leaves back until they’re just 2 or 3 inches long to help encourage growth.
12. Check the rhizomes for holes every year and discard any that have holes, as they might be infected with borers.
13. Irises are generally drought-tolerant and deer-resistant.
14. Good luck!!