The common Bearded Iris grows from a rhizome, a thickened, horizontal stem that stores food and water. Successful storage requires maintaining the viability of these rhizomes until replanting, primarily by keeping them dry and preventing rot. These instructions are tailored specifically for storing bearded iris rhizomes.
Initial Steps: Cleaning and Curing Irises
After lifting the rhizomes, gently brush off excess dirt. Do not wash them, as adding moisture increases the risk of rot. Trim the foliage back to a fan shape of four to six inches, and shorten the long, fibrous roots. This trimming minimizes moisture loss and makes the rhizomes easier to handle.
Inspect each rhizome for damage, such as soft spots, discoloration, or signs of insect activity. Cut away and discard any diseased or mushy sections immediately to prevent the spread of pathogens. Only firm, healthy sections should be kept for storage.
The next step is curing, which allows cut surfaces to dry and form a protective callus. Spread the rhizomes in a single layer in a warm, dry area with good ventilation, away from direct sunlight. Curing for one to two weeks at temperatures around 70°F (21°C) seals wounds and reduces the chance of rot during long-term storage. Some gardeners dust cured rhizomes with powdered garden sulfur for added protection against disease.
Optimal Conditions for Dormant Storage
Selecting the proper environment and materials for storage is important for maintaining rhizome health over several months. The ideal storage temperature range is cool, consistently held between 40°F and 50°F (4°C and 10°C). This range encourages dormancy and minimizes moisture loss. Temperatures below 35°F may cause damage, while temperatures above 50°F can lead to excessive dehydration.
The storage area must be dry and dark, requiring excellent air circulation. Airflow prevents the buildup of humidity around the rhizomes, which is the primary cause of mold and mildew. Basements, garages, or unheated closets that maintain the correct temperature range are suitable locations for this dormant period.
Rhizomes should be stored in breathable containers, such as shallow cardboard boxes with holes punched in the sides, wooden crates, or loose paper bags. Airtight plastic containers must be avoided completely, as they trap moisture and create an environment conducive to rot. For additional protection against drying out, the rhizomes can be individually wrapped in newspaper or placed on a layer of dry peat moss or wood shavings. Labeling each container clearly with the iris variety and the date of storage prevents confusion later on.
Mid-Storage Maintenance and Inspection
Rhizomes require periodic attention while in storage to ensure they remain healthy and viable. A full inspection should be conducted at least monthly, checking for fungal rot and excessive dehydration. A healthy rhizome should feel firm to the touch.
If a rhizome begins to rot, it will develop soft, mushy spots and may show signs of mold growth. Remove and discard any affected rhizome immediately to prevent fungal spores from spreading to the rest of the stock. If the storage medium or surrounding air feels damp, increase ventilation or slightly lower the humidity in the storage area.
If the air is too dry, the rhizomes may begin to shrivel or wrinkle as they lose internal moisture. For minor shriveling, a slight increase in ambient humidity can help. Consistent monthly monitoring allows for quick intervention before minor issues compromise the entire storage effort.
Transitioning Irises Back to the Garden
The storage phase concludes when conditions are favorable for replanting, typically in late summer or early fall. This timing allows the rhizomes to establish a robust root system before winter dormancy. Replanting should occur at least four to six weeks before the first anticipated hard frost in the region.
Before replanting, conduct a final, thorough inspection to confirm viability. Discard any rhizomes that have become significantly dehydrated, soft, or damaged. If the rhizomes appear overly dry, a brief soak in water can help re-hydrate the tissue.
When planting, set the rhizome shallowly into the prepared soil, with the top of the fleshy part exposed or just barely covered. Planting the rhizome too deeply is a common error that can encourage rot once they are back in the ground. This final step ensures the stored rhizomes transition successfully to active growth.