When to Plant Iris Bulbs: Growing Irises from Bulbs and Rhizomes

Irises are lovely flowers that come in a variety of colors. They can be grown from bulbs or rhizomes, and the most common bulb irises are the Dutch iris and iris reticulata. When to plant iris bulbs to enjoy them in full bloom?
Mia Clark
When to Plant Iris Bulbs

When to Plant Iris Bulbs in the Ground? General Rules

Many gardeners enjoy planting irises, as they are easy to care for and add a splash of color to the garden. However, timing is key. When to plant iris bulbs, so that they get enough time in the ground to be ready to bloom in the spring (for iris reticulata) or summer (for the Dutch iris)?

In general, it’s best to plant iris bulbs in the late summer to early fall, before the first frost. That’s when the bulbs are typically available in stores, so we recommend planting them immediately after purchase. This gives the bulbs time to develop roots before the ground freezes over.

Nighttime temperatures should remain at least 40-50 degrees Fahrenheit when you plant your irises. Once the ground freezes, the bulbs will go into dormancy until spring, when they will begin to grow again.

If you live in an area with mild winters, you may be able to get away with planting the bulbs a bit later in the season. However, it is always better to err on the side of caution and plant them earlier.

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When to Plant Iris Bulbs: Specific Recommendations

Have you decided to buy a specific type of iris? When to plant iris bulbs of that type won’t stray from the general guidelines, but here’s more specific advice.

  • For Dutch iris bulbs, plant them in September, October or November, or at the same time you’re planting your tulips or daffodils. They’ll bloom in late spring to mid-summer.
  • Reticulata iris bulbs should be planted in September or October, and they’ll bloom during the spring – together with snowdrops and before tulips.
  • Both should be planted in well-drained soil and in full sun. Place the bulbs about 3 inches apart from one another.
  • Use fertilizer to help your irises in early spring, about 6-8 weeks before bloom, and after they’ve finished blooming.

If you follow these simple rules, you’ll have a lovely display of irises in no time! Just be sure to plant the bulbs at the right time of year. Irises are perennial plants, so your effort will be rewarded year after year.

How to Find Out the Best Time to Plant Iris Bulbs in Your Area?

The best way to find out when to plant iris bulbs in your area is by checking with your local Cooperative Extension Service office. They’ll be able to give you a more accurate answer for when to plant iris bulbs in your particular climate.

You can also check the Farmer’s Almanac or your local news station’s weather forecast. Many news stations will give you a general idea of when the first frost will be in your area.

When to Plant Iris Bulbs in the UK, Ireland, or Australia?

If you live in the UK, Ireland, or Australia, the answer to the question of when to plant iris bulbs is a bit different.

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In the UK and Ireland, it’s best to plant your Dutch iris bulbs in August and September. They’ll bloom in May. For reticulata iris bulbs, plant them in August, September, or October, and they’ll bloom in April.

As for Australia, the best time to plant Dutch iris bulbs is in July and August. They’ll bloom in November and December. Reticulata iris bulbs should be planted in July, August, or September, and they’ll bloom in October or November.

When to Plant Iris Bulbs in Pots?

You can also grow irises in pots! The answer to the question of when to plant iris bulbs in pots is the same as for planting them in the ground. Be sure to use a pot that is at least 12 inches wide and has drainage holes. Fill it with high-quality potting mix, and then plant the bulbs about 4 inches deep and 3 inches apart from each other. Water regularly, and when the foliage starts to yellow, stop watering as much. This will help the bulbs form a flower stalk.

Can You Force Iris Bulbs Indoors?

Yes, you can force iris bulbs indoors! This means you trick them into thinking it’s spring, so they’ll bloom indoors during the winter.

To do this, you’ll need to start with bulbs that are not yet blooming. Plant them in a pot using the same method as above. Then, place the pot in a cool, dark place for about 12-16 weeks. This simulates winter conditions.

After 12-16 weeks, bring the pot out of hiding and place it in a sunny spot. Water regularly, and soon you’ll have blooms.

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What About the Species of Iris That Grow from Rhizomes?

There are also irises that have rhizomes – thick, fleshy roots – instead of bulbs, and these include:

  • the Bearded iris,
  • the Siberian iris,
  • the Louisiana iris,
  • the Japanese iris.

These irises can be grown from seeds, but it’s generally easier to grow them from iris rhizomes, which are typically available for purchase in the fall. They can be planted from late August to September.

Some gardeners also plant them in the spring, but it’s known that fall-planted irises establish themselves more quickly and bloom more profusely than spring-planted irises. For this reason, the fall is generally considered the best time to grow irises from rhizomes – the same as when to plant iris bulbs.

When you’re ready to plant them, dig a hole that is about twice as wide as the rhizome and just barely covers it. Plant it in well-drained soil, and water regularly. The rhizomes should be 6-12 inches apart.

Iris Bulbs Are Easy to Grow – Plant Them in the Fall

Have you decided when to plant iris bulbs yet? Remember, the key is to plant them in the fall before the first frost in a soil with good drainage! This gives them time to develop roots before the ground freezes over. With a bit of planning, you’ll have a beautiful display of irises in no time.

Do you have any tips for growing irises? Share them with us in the comments below!

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