When I moved into my house 12 years ago, the yard came with purple and white bearded irises that put on a gorgeous show every spring. While I busied myself with other garden projects, I didn’t touch the irises—honestly, I was a little scared to—and the blooms have dwindled to almost none because I’ve neglected a basic maintenance task: dividing the rhizomes every few years to revive plants and prevent overcrowding.
This year, no excuses: My irises need dividing, and now is the perfect time for it. Perhaps I can inspire other neglectful gardeners to make things right with their irises, too.
According to Country Living’s guide to growing irises, bearded irises are best divided and replanted from July to September in northern parts of the United States, and from July to early November in southern parts. The main thing is you want to give newly divided plants at least six weeks to get established before the ground freezes, which is why those of us in warmer areas have a little longer.
I have a tendency to procrastinate, so I’m trying to treat the early side of the time frame—late July—as a hard deadline. After all, this task is best done every few years, and I’m on year 12.
Ahead, here’s what the job of dividing my irises entails, according to the Country Living iris care guide by garden writer Arricca Elin SanSone, including how to replant the newly divided irises correctly. (Hint: Not too deep!)
If you have beardless iris, versus the bearded ones discussed here, refer to the full guide because the timing and steps are a little different for beardless varieties.
How to Divide and Replant Bearded Irises
Dividing:
- Use a fork or spade to get under and lift a clump of iris rhizomes out of the soil.
- Look for new baby rhizomes, which are called “increases,” all around the “mother” rhizome. (The mother rhizome will not bloom again, but the increases will.)
- Take chunks from the edges of the clump, keeping a leaf fan attached to each piece. Trim the leaf fans to 6 inches.
Replanting:
- Choose a sunny spot. I plan to plant in the same area, but I’ll also have more plants after dividing, so I need to make sure any new planting areas also get full sun.
- Work some compost into the soil.
- Place the rhizomes about 1 to 2 feet apart. This spacing will allow good air circulation, which will help prevent disease.
- Do not plant too deep, or you’ll stifle blooms. Plant the rhizomes just deep enough so that their tops still show above ground. Country Living’s iris guide refers to this as allowing the rhizomes to “sunbathe.” A gardening friend of mine gave me another helpful visual: When placed at the right soil depth, the rhizomes look a bit like ducks swimming in water.
- If mulching, do not cover the rhizome—just mulch up to it.
- Water newly planted irises well, and water again if you haven’t had rain in a week.
- The first winter, cover new plants with evergreen boughs or pine needles to protect rhizomes from the freeze-thaw cycle. After winter, uncover them again.
When it’s all said and done, I will likely end up with more iris plants, possibly even so many that I’ll have extras to share with friends and neighbors. Irises are a classic “passalong” plant for this very reason. But the biggest reward will come next spring when my iris blooms—hopefully—return in abundance. I’ll report back.
