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Siberian irises are garden treasures

This Siberian iris named Roaring Jelly shows the richness of color and beauty of form these irises possess.
This Siberian iris named Roaring Jelly shows the richness of color and beauty of form these irises possess. Observer file photo

After the wonderland of bloom by flowers in March and April, we now approach late spring, which often seems too green. With the trees in full leaf, the bulbs mostly finished and the azaleas on their ebb, the landscape looks distinctly different than just two weeks ago.

Yet, some treasures await in late spring, and one of them ranks among my favorite perennials of the entire year. It is an iris, but not just any iris – it’s the Siberian iris.

Now, a plant with Siberia in its name might seem an unlikely winner for the Piedmont Carolinas with its bright sun and heat, but it has proven to be a wonderful choice.

Like all irises, it bears beautiful flowers, typically for a few weeks starting in early May. But unlike some irises, it is trouble-free and the foliage looks good well into autumn. Its major merit is as a great perennial to fill the gap between the big burst of spring bloom in April and the wonderful summer flowers that open in early June.

Siberian irises are herbaceous perennials, meaning they produce fresh foliage every spring. These are tallish, narrow, vertical leaves that rise about 3 feet and are accompanied by tall stems bearing buds of the new flowers. Because the foliage is good looking, this iris deserves a prominent spot in a flower bed near the center or as a background.

This iris will tolerate moist soil but not a soggy place. It is, however, less susceptible to borers and rot than some other kinds of irises, which is why I think Siberians rank among the top perennials.

How to plant

Set plants about 2 feet apart to allow good development of the clumps. They grow from rhizomes which should be set 1 inch or so deep. Sun, or at least lightly dappled shade, is important for growth. Avoid planting them in the hottest areas of afternoon sun. You can expect to dig and divide clumps every three to five years, depending on the amount of growth.

Organic mulch such as compost will help the plants in the heat of summer by conserving moisture in the soil and keeping the roots cooler in hot weather, which help growth. The mulch also suppresses weeds.

Trim off spent flowers and the stalks for the sake of appearances, but leave the foliage alone through the summer and early autumn. It will begin to turn brown and wither in the autumn, and you can cut off the spent foliage about an inch or so above the ground.

Choosing Siberian irises for your flowerbed is a delight because the colors are so beautiful. Colors range from white, pink and pale yellow through many shades of light to dark blue and violet. Don’t hesitate to buy and plant now when you see them for sale.

Ask Nancy

Q. I want to get started with my eggplant and peppers. But the soil still seems cool after the weather earlier this week. Is it time for them?

A. I suggest waiting another week or so. Those plants demand warm soil for best growth and can easily wait until a stretch of warm weather raises the garden’s temperature, probably next week.