Bearded Iris (Iris x germanica)

There is a point each year where my garden looks a little like Monet’s famous garden, and I am clearly quite okay with that!  Each spring I am graced with a spectacular and long lasting display of some of the most beautiful and diverse blooms I have.

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*A handy growing summary chart is at the end of the article.*

I became a fan of bearded iris decades ago. There’s a home in town that I would regularly drive by that had this lovely spread of them growing (complete with name tags!). They were planted amongst an equally lovely array of roses. As the bearded irises would slow down in bloom, the roses picked up where they left off. I sometimes take a detour by that house even though my commute has changed, just so I can see this lovely garden.

Bearded irises are ridiculously easy to grow, but as always, as long as you make sure you give it the right conditions.  Bearded irises will not bloom if they are too shaded throughout the day.  They really do prefer full sun locations, even in hot zones.  The purple irises pictured didn’t bloom for years due to the shade of a tree that they had been planted under by a previous owner of our home.  We had the tree removed due to it being too close to the roof, and voila!  The next year they bloomed like crazy.

Being very drought tolerant plants also means that they will need well draining soil to avoid rotting of the rhizomes that they grow from.  If they are planted in heavy clay, you will likely see slow growth, so it is best to amend the soil first to loosen it and increase drainage.  You should also not plant them very deep for the same reasons.  Rhizomes (fleshy, specialized stems) are usually placed no more than 1 – 2 inches deep.

Bearded irises are typically planted in late summer to early fall.  This is long after flowering is done and the stress of summer heat is over, but still gives time for growth of the rhizome before winter.  However, the reality is that you can plant them at any time.  You just shouldn’t expect to see blooming right away.  The plants need the chill time of winter to signal the production of flowers.  They also need time to store energy in the rhizomes to be able to support their growth.  So even if you plant in fall, you may not see anything happen for a year or so, depending on how large the rhizomes were that you started with.

Most bearded irises bloom only once during the year in early spring, but the bloom can last for several weeks.  Some varieties will bloom again in the fall, though it may not be as much or last as long.  To help ensure a good display, be sure to remove spent blooms and flower stalks to prevent the production of seeds.  This saves energy for more blooms to form during that season, as well as to save energy throughout the year for next year’s flower formation.

The fact that your irises will be without flowers through much of the year means you will want to plant them amongst other plants for visual interest.  Bearded irises can be of varying height, so make sure they will not be lost behind taller plants, or dominate shorter ones.  Resist the urge to trim back any green leaves as the plant uses them for producing food that will be stored in the rhizome which will fuel the following year’s bloom.

Bearded irises are also notable for how well they self-propagate from the rhizomes.  Like other types of bulb-type plants, they will grow into a larger and larger patch of plants over time.  Eventually you will want to divide the cluster, usually after every 3 to 5 years.  This will reduce crowding which helps improve growth and flowering, and reduces the risk of pests and diseases from becoming too prevalent.  The best time to do this would be in the late summer to early fall, which is also their ideal planting time.

To divide the clumps, use a shovel to dig down into the ground at least 6-8 inches away from the outer edge of the cluster and several inches down and lift up the rhizomes.  You’ll want to be careful to avoid doing too much damage to the rhizomes, but they are pretty hardy as long as they aren’t diseased or rotted.  Continue lifting rhizomes out of the ground from the outside moving inward, until you have reduced the cluster to the size and location you want.  You can plant the removed rhizomes elsewhere in your yard, or pass them on to fellow gardeners.

Pests include aphids, iris borer, and slugs/snails.  Mostly the usual suspects.  The best method of preventing these organisms from becoming a serious problem is to ensure that you clear out old foliage each fall.  This keeps hiding places and egg-laying spots to a minimum, as well as prevent the buildup of debris that can trap excessive moisture that allows bacterial diseases and rot of the rhizomes.

Plant Summary:

• Perennial: Plants will live for several years, but should be divided at least every 5 years
• Deciduous: Leaves may stay green in mild winter areas
• Height: depends on variety, 1 – 4 feet
• Width: individual plants have only a few inches spread, but clusters can spread endlessly if not divided (spread is slow)
• Sun: full sun, will not bloom if regularly shaded
• Water: very light, drought tolerant
• Soil pH: neutral to slightly acidic
• Soil type: amend heavy clay or loose sandy soil
• Key nutrients: fertilize as you would for other flowers
• Planting time: best to start in late summer to early fall as temperatures drop
• Zones: 3 – 10