CHALLENGE: Just this week two southern California gardeners reported success with a new series of peonies, called Itoh Hybrids. (Ron Vanderhoff, Daily Pilot / April 22, 2011)

Serious gardeners love a challenge, especially when it comes to zones, frost, temperatures and all that boring technical stuff.

Tell a serious plant lover that you can't grow one, and they'll buy two. Tell them it's too tropical or too temperate, and they'll test it. Tell them it's too difficult to grow, and they'll dream about it all night long. Gardeners love to push the envelope.

Peonies growing and blooming in Southern California is precisely one of these local challenges. Just this week I received reports from Kathleen and Katharine, two women who accepted the peony challenge. To my surprise, both reported success with a series of peonies called Itoh Hybrids.

Kathleen moved to north San Diego County several years ago from colder climates. She missed peonies terribly.

"On a whim last year I decided that I really wanted to have one of the new Itoh Peonies, just to enjoy its beautiful blooms," Kathleen said.

Getting a newly acquired peony to bloom the first year isn't all that surprising, since they are brought here from colder climates, where they've already been exposed to a cold winter.

But Kathleen's peony didn't behave as expected. Once it was out of bloom, Kathleen forgot about it and stuck it under the shade of a tree fern.

"I completely neglected it by letting it sit in water," Kathleen continued. "I finally remembered the poor plant a few weeks ago when I noticed some new growth. Quickly I moved it into a little sunshine and last week … buds!"

A reblooming peony only a mile and a half from the ocean, with no winter chill and no special care, just lots of water? Hmmm, that's not supposed to be possible.

Then I heard from Katharine, who has been growing peonies for five years in her garden in Glendora. During that time she has amassed quite a collection, probably more than 25 plants, enjoying their blooms all the way into mid-June.

"I have discovered that the Itoh peonies are very vigorous early blooming varieties," Katharine said.

She babies her peonies with mulch, fertilizer and weed control. She reports no pest or snail problems on any of her plants.

Katharine said that, after this spring, she learned that she probably doesn't need to coddle her peonies quite so much. Katharine explained her reasons.

"One day, I asked my gardener to plant a Camellia and I forgot that the Itoh peony was sleeping underneath the location we were going to spruce up," she said. "The dormant plant was dug up by accident. He didn't know what it was, and the cheese curd-looking root ball laid out on the grass for a couple of weeks. Finally, I picked up the mass, planted it in a plastic container and sat it on my driveway. It loved the warmth of the concrete and is blooming even earlier than last year."

Katharine grows her Itoh peonies in full sun with some morning shade on the north side of her house.

"The plants really like my heavy clay soil, but seemingly like the richly fragrant potting soil as well," she said.

Perhaps not coincidentally, these peony success stories both involve a particular series known as Itoh peonies.

Named for Toichi Itoh, the first hybridizer to successfully cross a tree peony with an herbaceous peony, these peonies are prized for their huge, beautiful blooms and lush green foliage.

Itoh peonies grow with a domed, vigorous habit and produce large double flowers with disease-resistant, lacy, dark green foliage. They grow to about three feet tall and wide and, like all peonies, get even better with age. Itoh peonies also have an extended blooming period due to their ability to produce both primary and secondary buds.

A peony connoisseur, Katharine said that with traditional peonies the flowers are top heavy and flop, but with Itoh peonies their stems are much stronger.