Irises are celebrated garden flowers, known for their elaborate blooms and wide spectrum of colors. Finding the right plant stock is crucial for success, but irises grow from two different types of underground storage structures. Knowing where to look depends entirely on understanding the difference between a true iris bulb and a fleshy iris rhizome.
Understanding Iris Types: Bulbs vs. Rhizomes
The physical form of the iris stock determines its growing requirements and purchasing season. Bearded Irises (Iris germanica) grow from thick, fleshy, horizontal structures called rhizomes, which are modified stems. These rhizomes typically sit right at or slightly above the soil surface to absorb warmth from the sun. In contrast, many smaller iris varieties, such as Dutch Irises (Iris hollandica), grow from true bulbs. A true bulb is a compact, globe-shaped modified bud, similar to those of tulips, and is planted fully underground. This distinction is important because rhizomes and bulbs are often sold at different times of the year and at different retail locations.
Where to Purchase Iris Stock
The best source for iris material depends on the variety desired and the level of selection needed.
Specialty Nurseries
For the widest selection of Bearded Iris rhizomes, especially new or rare cultivars, mail-order specialty iris nurseries are the premier source. These companies offer hundreds of varieties and provide stock that is freshly dug and true to name, often including bonuses with larger orders. Specialized growers usually only ship during the peak late summer planting window.
Local Garden Centers
Local garden centers and nurseries are reliable sources for common and regionally-adapted iris varieties. These businesses often sell potted rhizomes and bulbs, which allows for planting outside the ideal seasonal window. While the selection is smaller than mail-order, local experts can offer immediate advice on varieties suited to a specific climate.
Mass Retailers and Clubs
True iris bulbs, like Dutch Irises, are commonly found at big box stores and mass retailers, typically packaged in mesh bags with other fall-planted flower bulbs. This option offers convenience and affordability, but the quality control can be less consistent, and the variety selection is limited. Locally-adapted rhizomes can also be found through iris societies or garden clubs, which frequently host local sales and swaps, often providing healthy, divided stock directly from local gardens.
The Best Time to Buy and Plant
The success of a new iris plant is heavily dependent on purchasing and planting it during its optimal season. Rhizome irises, such as the Bearded varieties, are best bought and planted during the late summer months, spanning from July through September. This timing allows the rhizomes to establish a robust root system before the onset of winter dormancy and the ground freezes. Planting during this period ensures the plant has sufficient time to anchor itself before its spring bloom cycle.
True iris bulbs require a cold period to initiate spring growth and are typically purchased and planted in the fall. This timing is similar to other spring-flowering bulbs, requiring them to be in the ground after the intense heat of summer has passed but before the soil freezes solid. If true bulbs are purchased in the spring, they are usually sold already potted and actively growing.
Checking for Quality and Health
Regardless of the source, a close inspection of the plant material is necessary to ensure a healthy start in the garden. A healthy iris rhizome should be firm to the touch, with no signs of softness, mushy spots, or a foul odor, which indicates rot. Look for a clean, cream-colored appearance on the attached roots, indicating vigorous growth.
Iris bulbs must also be firm and free of any visible mold, dark spots, or deep cuts. A larger, heavier rhizome or bulb is preferable, as it contains more stored energy and is more likely to produce a strong bloom in the first year. If purchasing online, unpack the order immediately upon arrival to check for proper dryness and healthy appearance, and contact the vendor if damage is apparent.