Determine when to plant iris bulbs and you can enjoy these sensational blooms from early spring through summer. With distinctive, elegant petals and exquisite markings, they never cease to impress.
Choose from early flowering varieties with their delicate flowers and delicate fragrance or opt for one of the many taller European types such as Dutch, English and Spanish which come into their own midsummer. These tend to come in a wider range of colors and have taller, longer blooms on dark green, sword-shaped foliage.
You can grow irises happily in free-draining soil and like to bloom in a sunny location, but some will tolerate partial shade as well. Long-lived and fairly hardy – thriving in USDA hardiness zones 3-9 – they will last for several years with very little care and attention. Not to be confused with rhizomatous irises, bulbous types need an annual cold dormancy period to build up energy reserves ready to bloom again the following year.
When to plant iris bulbs
Depending on whether you want small, early blooms or bigger mid-summer blooms, this spring bulb guide is packed with expert advice, helping you know when to plant iris bulbs with confidence.
When to Plant Spring-Blooming Irises
“Iris bulbs should be planted in the fall because they need a long period of cold temperatures to set their flower buds,” advises Venelin Dimitrov, product manager at Burpee. (opens in a new tab). Plant bulbs in the fall as soon as possible after you receive or purchase your bulbs.
Dimitrov also says, “Choose a site in full sun or light shade with good drainage where water does not sit on the surface after a rainfall event. Bulbs thrive in well-drained, moist soils. Mulch the soil to protect the bulbs from the heat of the strong summer sun.
Smaller spring-flowering irises such as Iris reticulata and Iris danfordiae will fill your garden with color and fragrance in February and March, when very few others are in bloom. Great planted in clumps and naturalized in grass, under hardwoods, they can create carpets of blue, white and yellow with very little effort. Their open, graceful flowers – with a trio of upright petals among three drooping “falls” or longer petals – are a very valuable and popular food source for early emergent pollinators.
When is the best time to plant summer flowering iris bulbs?
Irises are also some of the best summer bulbs. Again, it is important to plant the bulbs in the fall well before the first frosts.
“Dutch irises, like bearded irises, grow from bulbs and need a cold period to bloom,” says Annette Coppess at Breck’s. (opens in a new tab). “Try planting these smaller bulbs in early fall, after the weather has cooled, but before the ground gets extremely cold. These bulbs will need cooler, but not freezing, temperatures to settle into their new home before winter.
Reaching about 20 to 23 inches (50 to 60 cm) tall, these large, showy flowers are fantastic outdoors in borders and pots and also make brilliant cut flowers. With colorful blooms in a huge range of striking and unusual shades – including azure blue, lime-tinged white and copper blush pink, each flashed with a golden eye – they are surprisingly cheerful and very demanding. little attention.
When to plant irises in pots and planters?
As with all bulbous irises, they are best planted in the fall, as they need a cold period to encourage them to grow. If you fancy growing these reliable garden beauties in pots and planters, keep in mind that some types of irises are more suitable than others.
Paul Blom from the Bloms Bulbs specialists (opens in a new tab) says, ‘The adorable dwarf irises are among the earliest spring bulbs and provide the richest colors and are particularly suited to the rock garden or pots and small containers. While the Dutch, English and grassy types feel more comfortable on the border.
Thanks to their early bloom time and small bulb size, dwarf irises are ideal candidates for layering with other spring-flowering bulbs. Known as “bulb lasagna”, it’s a popular and easy way to plant a single container and ensure a succession of blooms that will last for weeks.