What a cold and wet Memorial Day weekend! I am not sure if it broke any records but it was 37 degrees F Friday night and I was pretty glad that my tomatoes and peppers were still in pots so I could bring them inside! Sometimes being a bit behind in gardening activities may be for the best!
While finishing planting of the vegetable garden has been momentarily put on hold, that actually gave me a bit of time to observe and absorb what is happening in my flower beds and this weekend, irises are beginning to strut their stuff. I think I fell in love with irises when I was about 4 years old and visiting by grandmother in Buffalo. She had the most amazing purple iris in her garden that that smelled just like grape Kool-Aid. Although that was more than a half century ago, I have always planted or nurtured irises everywhere I have lived.
I am not alone in my iris obsession! Irises have played a prominent part in lore, legend and religion for over four thousand years. According to the ancient Greeks, they were the personification of the goddess, Iris, who was the messenger of the gods and the rainbow which linked earth to other worlds. Iris would escort souls to another life along her iridescent bridge. Iris flowers were placed on the tombs of women and later Muslims planted white irises on the graves of fallen soldiers.
Of the 200 plus species, those most commonly grown in New England gardens are the tall bearded, Siberian, Japanese, netted and crested irises. I have had reasonable success with the bulbous Dutch iris and I. bucharica, native to Afghanistan, as well.
Iris blossoms vary greatly in shape, color and size but their overall structure is similar. Each flower consists of three upper petals called standards and three lower or outer sepals referred to as falls. Irises are divided into two major groups; those arising from rhizomes, which are horizontal stems growing at or slightly below the soil surface, and those growing from bulbs.
Some gardeners lament the relatively brief annual flowering period of irises. And it is true that even in good years weather-wise you cannot expect more than two or three weeks of a spectacular show. These folks can be comforted to some extent by choosing early, mid-season and late species and varieties of irises so the blooming period is prolonged. I like to think about it more like a special holiday one looks forward to each year. It just wouldn’t be appreciated as much if it occurred more often. And irises are just too magnificent to be taken for granted.
Taller irises make a nice backdrop for lower growing perennials. Shorter species, like the miniature bearded iris, or the crested iris (Iris cristata) look best planted in drifts in the front of the garden.
As far as the tall bearded irises go, your color choice is virtually unlimited. Lovelier shades become available each year. Also known as, German bearded irises, they prefer a sunny, well-drained site with adequate moisture. They reach two to three feet in height (although the stand at our local bank is at least 4 feet tall!) and come into bloom from mid-May through early June.
Siberian irises bloom slightly later than the bearded irises. They also grow from rhizomes but the rhizomes are quite small and they readily form a fibrous root system. Colors of Siberian irises are somewhat limited compared to their bearded cousins. They range from white to blue, purple, violet and wine red. Their foliage is slender, almost grass-like.
Japanese irises flower in early to mid-summer and can grow up to four feet tall. A fallacy concerning Japanese irises is that they need wet conditions to do well. In truth, they will grow in almost any well-drained, organic, slightly acidic soil as long as adequate moisture is supplied.
Another fallacy is that irises should not be fertilized. Mine seem quite appreciative of nutrients both during early spring growth and about a month after flowering. The bearded irises go into a resting stage after they bloom which lasts about a month. Then they begin to produce new roots and leaf buds. Each rhizome only produced flowers once and then it retires to function solely as a food reservoir.
Division of bearded irises is best done in late summer. Use a sharp knife to divide the rhizomes making sure each mature rhizome has one or more new leaf buds attached. Fans of leaves should be pointing in the direction you want the plants to grow. I generally cut back the leaves to six inches or so when dividing to make handling the plants easier. Position the plants so the top of the rhizomes are at or slightly below the soil surface.
While Siberian and Japanese irises are rarely bothered by pests, iris borers can be a problem with the bearded iris. Larvae hatching from eggs laid the previous fall will feed on leaves then burrow into the rhizome creating wounds that can then be colonized by bacterial rot. Infected rhizomes will be mushy and foul smelling. Control consists of removal of dead leaves in the fall or early spring. If borer damage is noticed, usually because of zigzag feeding injury on leaves, dig up the clump, find the larvae and dispose of them. It is a good idea to dig and divide bearded irises at least every third year to scout for these pests.
Few perennials are as hardy as irises and provide you with a rainbow of color in late spring and early summer.
Happy Gardening to You!