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    Save the Date: Perennial Plant Society’s 30th Plant Sale is April 4, 2020, 9 a.m. – 1 p.m. at the new Expo 3 Building at The Fairgrounds Nashville. Here’s where you can find the newest varieties of perennials, shrubs, vines and annuals from local growers, along with long-time, never-fail favorites, ready for spring planting. Learn more at the PPS website.

     

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Grow Siberian iris from seed

I have several Siberian iris pods that have dried and split and produced seeds. Can I plant them to grow new irises? When is the best time to plant?

Siberian iris croppedAfter the irises bloom in the spring, they may form seed pods, and those ripe seeds (which should be dark and shiny) can be saved and planted to grow new irises. But they require specific conditions to germinate successfully, including a period of cold weather, so the best time to plant iris seeds is in late fall and winter.

Iris experts suggest two ways of germinating iris seeds. This information comes from Margie Valenzuela of the Tucson Area Iris Society and Sally G. Miller at the Dave’s Garden online community of gardeners:

Soak the seeds in water for at least 48 hours, or for several days, changing the water every day. This causes the seeds to plump up and allows them to germinate faster. Plant the seeds about a half-inch deep, about a half-inch apart in a planter box filled with seed-starting potting mix, and keep the soil moist (but not wet) at all times. You may want to cover the container with wire mesh to keep squirrels from digging in the pot. You can also plant the seeds directly in the ground this winter, in a prepared bed. When they begin to germinate, iris seedlings look a bit like grass, but the leaves soon acquire their typical flattened growth pattern.

Other experts provide information about growing seedlings indoors, under lights. They still need a period of chilling – about 12 weeks in the refrigerator, after soaking the seeds in a sterilizing solution of one part bleach and ten parts water. After they’ve had their chill, plant the seeds in seedling mix and grow them under fluorescent lights indoors, moving the seedlings to the prepared garden bed as weather permits, and keep them well-watered during the first year.

Irises grown from seed may not bloom the first year. And when they do bloom, you may find they don’t emerge as the exact plant that grew them – they likely will be interesting hybrids, fertilized nature’s way by bees and other pollinators.

Divide irises after they bloom

Our bearded irises are coming up and they’re pretty crowded this year, and need to be dug up and divided. If we divide them now, before they bloom, will we still have flowers this year?

Purple irisIf your iris bed is crowded but still producing blooms, it is best to wait until later to dig up the iris bed and divide the rhizomes. The experts at the American Iris Society and other sources say iris beds should be divided every three to five years, and suggest mid- to late-summer as the best time for this task.

When the time comes this summer, here is the method suggested by author Judy Lowe in Month-by-Month Gardening in Tennessee & Kentucky:

Cut the leaves in a fan shape about 6 inches tall, then lift the clump with a spading fork, wash off the dirt, and inspect the rhizome for soft spots, damage or disease.

Cut the rhizome into smaller pieces with a sharp knife, making sure each piece includes an eye or a bud. Cut away any older growth. Lowe notes that iris rhizomes are susceptible to fungal problems, and suggests dipping the rhizome briefly into a solution of one part liquid bleach to nine parts water.

Replant the sections: Dig a hole and make a mound of soil in the center, then place the rhizome on top so that its roots spread over the mound. Cover the roots, but maintain the rhizome at soil level or just below it. Bearded iris rhizomes that are planted too deep may rot, she says. Water the bed well.

Dividing in summer allows the rhizomes to become established before the end of the growing season, and more likely to bloom well next spring.

Color Garden book giveaway

Thanks to readers who left comments this week for a chance to win The Nonstop Color Garden by Nellie Neal. Constance is the winner of the random drawing.

Nellie, her book, and information from Doris Weakley of the Perennial Plant Society of Middle Tennessee were featured in a story in last Saturday’s Tennessean. You can read it here.

And watch for another book giveaway soon.