How to Store Iris Rhizomes for Success Next Season

Iris are treasured for their elegant orchid-like blooms that add a touch of splendor to the garden in late spring. While you can find iris bulbs to plant each year, perennial garden irises are grown from rhizomes. Proper storage of these rhizomes between growing seasons is crucial for the best flowering results.

With a little knowledge of iris biology and some simple storage methods, you can easily keep extra iris rhizomes viable from one year to the next

Why Iris Rhizome Storage is Important

Iris consist of thick, fleshy underground stems called rhizomes, which store food reserves and energy to fuel growth. In summer, rhizomes expand, sending up leafy fans and upright bloom stalks. After flowering finishes, the greenery dies back as the rhizome goes dormant for winter.

The following spring, completely new growth emerges from the rhizome. This makes iris one of the “reblooming” perennials. However, the rhizome must remain healthy over the winter rest period to reflower the next year.

Iris rhizomes you dig up in late summer or fall while dividing old clumps have an abundance of stored energy. But without proper storage, they will gradually desiccate and lose viability. Proper handling keeps rhizomes plump and vigorous until you can get them planted.

When to Dig and Store Iris Rhizomes

In areas with cold winters, the best time to divide and dig iris rhizomes is late summer after bloom season finishes. Rhizomes can also be dug in early autumn up until the ground freezes.

In warm winter climates, dig and divide iris in late fall or early winter while they are still semi-dormant. Avoid disturbing them during active growth periods.

Getting Rhizomes Ready for Storage

Here are the steps for preparing freshly dug iris rhizomes for storage:

• Trim foliage – Cut leaves back to about 2-3 inches from the rhizome. Don’t remove them completely.

• Clean gently – Use a brush to lightly clean off soil clinging to the rhizome. Avoid washing as moisture encourages rot.

• Let dry – Place rhizomes in a single layer and allow to dry for 1-2 days. Drying enhances dormancy.

• Cure – Further dry rhizomes for 1-2 weeks in a dark, dry, well-ventilated area around 70°F.

• Treat – Dust with sulfur powder to prevent fungal issues.

The curing period enhances dormancy hormones within the rhizome so it is primed for storage. Proper drying and curing prevents rot and desiccation during storage.

Selecting the Best Rhizomes for Storage

As you divide clumps and handle the rhizomes, evaluate each one and discard any that show:

• Soft, mushy spots indicating rot
• Extremely tiny size with no vigor
• Damage from iris borers or other pests
• Evidence of disease

Focus on storing the largest, healthiest rhizomes with good firmness. Small bits or pieces with minimal roots often fail to establish well when replanted.

Ideal Storage Conditions for Iris Rhizomes

Iris rhizomes require cool, dry conditions with excellent air circulation during storage. Avoid storing them in:

• Direct sunlight
• Temperatures below 36°F or above 50°F
• Humid environments

The ideal temperature range is 40-45°F. Storing rhizomes at warmer temperatures around 70°F accelerates loss of dormancy and premature sprouting. Extended storage in cold below 35°F damages rhizomes.

Good air flow around the rhizomes is crucial to prevent rot. Enclosing them in plastic encourages harmful moisture accumulation and fungi.

How to Store Iris Rhizomes for the Winter Months

Here are two effective methods for storing iris rhizomes:

The Box Method

• Find a shallow, sturdy cardboard box or make one by cutting down a larger box.

• Punch numerous holes in all sides for ventilation.

• Place a thin layer of peat moss in the bottom to absorb moisture.

• Arrange prepared rhizomes in a single layer without crowding.

• Store box in a sheltered spot like a garage or enclosed porch around 40°F.

The Stocking Method

• Place individual rhizomes or small bundles into old nylon stockings.

• Tie a knot between each rhizome to keep them separated.

• Hang the stockings in a cold, dry basement or unheated room.

• Maintain temperatures between 40-50°F and avoid direct light.

Either approach allows air to freely circulate around rhizomes. Check them periodically over winter and remove any that show signs of rotting. Relocate any sprouting rhizomes to a refrigerator.

What to Do with Rhizomes After Winter Storage

Once spring arrives, stored rhizomes can be planted or gifted to gardening friends. Follow these tips:

• Inspect overwintered rhizomes and discard any that are damaged or dried out. Keep only the most vigorous ones.

• Soak rhizomes in room temperature water for 1-2 hours before planting to rehydrate.

• Trim back old foliage to 1 inch above the rhizome before planting.

• Cultivate soil and add organic matter like compost before planting.

• Space rhizomes 12-24 inches apart in full sun to partial shade.

• Plant the top of the rhizome just at or slightly above soil level.

With attention to proper harvesting, curing, storage conditions, and spring planting, your stored iris rhizomes will thrive and flower beautifully the following season. Dividing and sharing rhizomes allows you to expand your iris collection at no cost too!

Storing Other Flower Bulbs Alongside Iris Rhizomes

The techniques for storing iris rhizomes also work for other spring-blooming flower bulbs, including:

• Tulips
• Daffodils
• Crocus
• Hyacinths
• Snowdrops

Prepare bulbs by gently brushing off any clinging soil after digging. Allow to dry and cure just like iris rhizomes before placing in ventilated boxes or stockings.

Aim for cooler temperatures around 40°F to prolong viability of tulip and hyacinth bulbs. Take stored bulbs out of temperature-controlled conditions in early spring so they thaw and break dormancy on schedule for planting.

With a little effort, you can successfully hold onto extra bulbs and rhizomes from season to season. Proper storage keeps them alive and blooming beautifully when you finally find their perfect spot!