Water gardens are all the rage. However, if your water garden is coated with green pond scum this summer, it may be due to algae build-up. Small amounts of algae are good for ponds, providing food for fish. But when algae takes over, it can be unsightly and harmful, choking out other aquatic life. Chemical algicides are available to control algae blooms, but many gardeners are hesitant to use them.
In the 1990s researchers in England began experimenting with using barley straw as an organic control of algae growth in ponds and waterways. The theory is that as barley straw decomposes in water, it releases lignins. These are oxidized into humic acids when exposed to oxygen. If sunlight then shines on the humic substances, hydrogen peroxide is formed. Hydrogen peroxide inhibits the growth of algae, but has no effect on existing algae. Since it is released in small doses over time, it can be effective in keeping algae out of ponds for months.
When using barley to prevent algae growth in your home pond or water garden, keep in mind these suggestions.
* Chop up the barley and place it in plastic netting so it can float on the water. It's important the barley decomposes aerobically (with oxygen) to be effective.
* Place barley in shallow water (4 to 5 feet deep) where it's most effective.
* At water temperatures below 50° F, it takes 6 to 8 weeks for the barley to produce enough peroxide to inhibit algae growth. It takes only 1 to 2 weeks at water temperatures above 68° F.
* Once decomposing, barley straw is effective in controlling algae growth for 4 to 6 months.
For a summary of research in this country and abroad on barley straw controlling algae growth, check out this Web site: www.btny.purdue.edu/Pubs/APM/APM-1-W.pdf.