Divide and Conquer: Split Iris and Peonies

Back in late May I was looking at my small collection of bearded iris that were blooming, and my paltry collection was in desperate need of another color. There was plenty of the standard whites, and blues with variations and combinations, but something was missing. For whatever reason, I decided it was yellow.

Weeks went by until I fired off an email to Schreiner’s Iris Gardens (schreinersgardens.com) out in Oregon and asked them for suggestions. Why do hours and hours of research (my usual modus operandi) when I could simply ask the experts? They did and made two suggestions, Garden Time and Here Comes the Sun.

At about the same time I was getting upset with my peony collection. My database says I have over 20 varieties, but the garden has changed so much over the years that many are now hidden, boring varieties or in the trial garden waiting from who knows when to go into the gardens. I made some notes, tagged some of the plants, many of which need rejuvenation and moved on. I should have ordered new ones, but that would have entailed research when I was in the midst of the June drought followed by the summer deluge. The peonies were forgotten. Until now.

Two weeks ago I walked into the post office and my cheery postmistress says, “Andrew, you have a box of live plants!” What had I ordered and forgotten about or what breeder was sending me perennials to add to the trials? Neither. It’s shipping time for iris growers, and sure enough, my six, single fans of two varieties of yellow, tall, bearded iris had arrived.

This should be enough to give you a clue that it’s not only time for planting iris — and peonies, but they can wait a bit — but for dividing those that have ceased to bloom. Yes, you will hear from other gardeners and the less informed that iris and peony plantings can be left in place for years. In fact I did some pilfering from an iris garden that was probably planted 100 years ago and probably hadn’t flowered for the past 50 of them.

Both bearded iris and most peonies send up new shoot growth from their tubers and rhizomes as these sub-surface appendages continue to grow and elongate. But as they begin to crowd themselves the new growth and new bud eyes diminish, and over time they cease flowering. The plants will continue to throw up foliage every year but you’ll notice fewer and fewer flower stems until there are none.

The solution is remarkably simple but does take a little bit of work. If you’ve got an iris bed or just a few plants that aren’t thriving they simply need to be dug, inspected, and divided. Likely you’ll end up with more divisions than you have space for planting so the worst of the lot — the rotted or gnarly pieces — just get thrown away. The balance get replanted or given to friends and neighbors. But now is the time.

Bearded iris rhizomes are easy to dig and just as easy to plant. But first, they need to be trimmed. Remove the foliage so all that’s left is about 3 to 4 inches of leaves also known as the “fan.” This eliminates a lot of the transplant shock and stimulates new growth once replanted. Compost or trash the cut foliage and don’t leave it in the garden. Next, using a garden fork, push the fork tines into the ground trying to avoid the rhizomes. It’s not always possible. When the fork tines are about 6 to 8 inches into the ground ease back on the handle forcing the rhizomes to break and come to the surface. Repeat as necessary until the bed is empty or at least thinned.

When the rhizomes come out of the ground gather them, one variety at a time, and inspect them. Throw away rotted or suspect sections then decide how you’ll cut the rest. You can use a long knife with a 6-inch blade for this work, and the object it to end up with as many healthy two-to-three-fan divisions as you can (see photo). Let the fans air dry, out of the sun, for about a day then replant. A one-eye division may take two years to flower but a three-fan division may flower next spring. A mix of one-fan and three-fan divisions will give you a new Iris bed that won’t need attention again for four to six years. If you replant only three-fan divisions your next renovation may have to be sooner. Two-fan divisions? Go for it.

Now, there is one mistake you can make at planting time that will result in no blooms ever, and that’s planting the rhizome too deep. The top of the rhizome and even the white part of the fan where the green foliage meets the rhizome itself should not be buried with soil. The fan should be mostly vertical to the soil and the rhizome horizontal and ever so slightly peeking out.

Inexperienced gardeners freak out at this step, and their common fear is that the rhizome, being so close to the soil surface, will freeze and die in the winter. If you get this work done now, new roots will anchor the rhizome and freezing won’t ever be a problem.

In a few weeks you can start doing renovations to your peonies. In fact, growers like Peony’s Envy (peonysenvy.com) are shipping now, though the best choices are probably sold out. May and June are the best times to order for late-summer planting, but take a look anyway. Something still available may strike your fancy.

No fertilizer when planting either of these, but they can both be lightly fed in the spring just before they peak and bloom. Water them in at planting, lightly if the soil is wet and deeply if the soil is dry.

Peonies don’t do well is shade. If you are lucky enough to find the Japanese woodland peony this is the only one that is shade tolerant, but frustratingly slow to establish and put on a good show.

Remember that with both peonies and bearded iris you can get an extended season of bloom by carefully ordering early-, mid- and late-season bloomers. This is usually noted in the catalog listings as are the blooming heights. Also ask friends if they have any tubers or rhizomes that they need to pass along. For great displays pass up those boxed and bagged offerings at the big box stores. Most of these are Dutch imports and probably not the varieties or quality you’re looking for. I was told over the summer by an importer that the Dutch consider us to be horticultural idiots, “and the Americans will buy anything.”

Do not plant iris rhizomes or peony roots in the spring unless they have been potted and overwintered in large pots. You’ll see them for sale, but they’ve been in refrigerators all winter and are certainly not the top of last year’s crop. Spring is the wrong time to plant these two perennials, and the Dutch do not send us the best of their lots. In the spring these plants should be flowering and not desperately trying to grow their roots in warming soil. It’s the cooling soil that stimulates their root growth, and that’s why they’ve been traditionally late-summer and early-fall planted. Buying them in the spring is just a marketing ploy, and my experience is that iris and peonies planted from tubers and rhizomes in the spring rarely perform as well as those that are fall planted. Don’t be suckered. Be a wise plant buyer unless it’s something you just have to have. It happens. Keep growing

GARDEN NOTES

You know the drill. This is the best time of the year to overseed your lawn, renovate it and seed new areas. For those who are still willing to use herbicides late in September and into October is the best time to use broadleaf weed control for pests like dandelions, creeping Charlie and plantain. Plantain is probably best pulled out with the root as it’s going to seed now, but immature plants will succumb to an appropriate herbicide. Too late for crabgrass control; this should be done in the spring with a preemergent. Learn the difference between your annual weeds and the perennial ones. Most herbicides are specific to one or the other.

If ever there was a year to plant trees (including fruit trees), bushes and shrubs, this is the year. The ground is moist, and you don’t have to guess if the nurseries have been watering their stock. Mother Nature did plenty of that.

No it’s not you. It hasn’t been a good year for a number of garden vegetables including tomatoes, melons, cucumbers, peppers and eggplants. On the other hand it’s been a remarkable summer for leafy greens. Keep on planting the greens, and they’ll continue to grow into early November. Look for cut-and-come-again types like Johnny’s Cheap Thrills, Renee’s Asian Baby Leaf and her Baby Leaf Heirloom Cutting mix. Plant in small blocks, and as long as you cut they’ll come back. Don’t forget radishes for their spicy foliage as well as the roots.

Don’t forget to order your garlic bulbs. They don’t get planted for about six more weeks but many vendors sold out early last year.