Irises have been my favorite flowers since I was about eight years old. I adored a cluster of brightly colored bearded irises that grew in a ditch near my house. As I grew older and began to understand botony more clearly, I realized that these irises were serving an important ecological purpose– they were helping to purify water that flowed through the ditch.
Water pollution from runoff is a serious problem in urban, rural and suburban environments. One of the most significant water pollution concerns is nutrient pollution, which contributes to a river-killing process known as cultural eutrophication. When nutrients from sewage, pet waste, food scraps and fertilizer run into our rivers, they contribute to the overgrowth of algae and the subsequent die-off of benthic plants, fish and invertebrates.
A responsible gardener can help to minimize his ecological impact by cultivating plants that purify your runoff water. Common species of ornamental iris, including bearded, Dutch, English, rabbit-ear an yellow iris, are particularly useful plants for purifying water.
To use irises to purify water, select a strain that you want to grow. There nearly 300 species of iris, as well as hundreds of thousands of sub-species, cultivars, hybrids and varieties. Fortunately, all irises accomplish the important task of purifying runoff water by removing carbon dioxide, acids and nutrients from it. Choose a variety that is easy to cultivate in your area, and purchase at least a few dozen bulbs of that strain. Choose highly water-tolerant varieties, such as yellow iris, if your target planting area is frequently submerged.
Plant your irises in a part of your lawn or garden that collects runoff water– a ditch is ideal.
Because I live on a hill, I chose to plant my irises in the ditch that naturally collects water at the foot of my lawn. Choose the most low-lying area of your property to plant irises for runoff water purification, or simply line the perimeter of your garden with them to collect any of your excess fertilizer.
All varieties are iris are best planted in autumn. Depending on your climate and USDA zone, you may need to plant irises relatively early or late in the year to see next-year blooms. As soon as the growing season begins again, your iris plants will be at work eliminating runoff pollution. Plant irises at a depth, spacing, soil-type and sunlight range appropriate to the variety; understand that iris needs vary tremendously between species and varieties.
As a gardener– or anyone who engages in the universal act of nutrient pollution– you can minimize your water runoff footprint by cultivating plants that eliminate this waste. Visit your local home-and-garden store or nursery to get started cultivating irises in your area.