Q: This year my iris did not bloom. What should I do to get flowers next year?
A: There are at least three reasons why your iris stopped blooming: lack of sun, incorrect planting depth or overcrowding.
Irises are hardy plants and relatively trouble free. In order to bloom they must be planted in a sunny location that receives a minimum of six hours of sun a day. Perhaps a nearby tree or shrub has grown over the years and now casts a shadow over your iris. A once- sunny area may now be too shady for it to bloom.
Iris grows from a rhizome, a potato-like growth, which should be planted just slightly below the soil surface. Plant it too deep and it will not bloom well. As the iris grows the rhizome comes to the soil surface, a desirable thing.
Irises multiply each year and eventually will crowd themselves out. As the iris clump becomes more and more crowded its blooms will decrease until they stop blooming altogether. A good rule is to divide your irises every three to five years. Do this after it has finished blooming, from July to September.
Irises prefer a soil pH in the neutral range. One to 2 inches of mulch between clumps will suppress weeds. Do not cover the rhizomes with mulch; grass or weeds growing between the rhizomes as well as any debris (dried leaves, etc.) should be removed by hand. The iris bed should not be covered except in very severe winters. Use pine boughs or other loose material — and then remove it in the spring.
The most common pest is the iris borer, which lays its eggs in debris around the iris. It then enters the iris leaves and makes tunnels down to the rhizome, eventually destroying it. The borer looks like a little pink worm. Remove any affected parts of the iris to prevent further damage.
Meet the needs of your iris and it will reward you with beauty and color — after all, Iris is the name of the Greek goddess of the rainbow.
Celia Juris, Bardonia, master gardener with Cornell Cooperative Extension of Rockland