by Lia Andrews. Water quality is a big deal, especially when it comes to orchids. Barb and Gary Murza found this out the hard way when they moved from Miami to Sanibel a few years ago. Over a period of a few months they lost 90% of their orchid collection. Gary Murza, a water treatment expert, discovered that the main culprit were chloramines; cheaper, less effective, but longer lasting chlorine substitutes.
Chloramines have been used in U.S. drinking water for 90 years, but is being much more in the last decade. Like chlorine, chloramines kill bacteria and other microorganisms. The difference is chloramines remain active longer, and have a lasting effect on suppressing beneficial bacteria and adversely affecting the plants themselves. Chlorine and chloramines (as well as dissolved solids) can also interact with certain fertilizers and render them ineffective.
Certain plants are particularly sensitive to chlorine and chloramines: african violets, ferns, and of course orchids. Only carbon filters can remove these chemicals from treated water. Phragmipediums are so sensitive that they require rainwater to thrive. Murza, a phragmipedium expert, says that watering this species with filtered city water means certain death within 6 months.
Chlorine and its substitutes aren’t the only issue. Various dissolved solids can react with fertilizers to produce unknown results. High levels of chlorides (salts), always an issue in seaside communities, mean a faster build up of salts in orchid pots, forcing orchid growers to repot more frequently; often yearly instead of every 2-3 years. (This is one reason many Florida growers mount their orchids on wood. Be sure to choose an ironwood, such as cypress or mahogany, that will withstand the high humidity.) Water pH is also important, especially since fertilizers are meant to be used with water in the range of 7.0-7.2. (For example manganese and iron aren’t absorbed at a high pH).
TESTING YOUR WATER
When testing water, Murza looks at pH, total dissolved solids, and chlorides (salts). The table in the pdf linked below shows water tested from four Lee County water treatment plants and other areas in Florida for June 2016 on page 1, and May 2016 on page 2.
When analyzing water you look at Total Dissolved Solids and Chlorides (salts=salinity). The high number of dissolved solids and salts make Lee County has some of the worst water in the state, along with Danier in Broward County and Branden outside of Tampa (very high silicon). The government used to set the limit for safe drinking water at 500 ppb dissolved solids. The Gladiolus/41 area of Fort Myers has the best water in Lee County. Murza explains that in May all water in Florida tends to be worse because that is when Florida flushes its pipes with high quantities of chloramine.
TYPES OF WATER FILTERS
There are two main types of water filtration: reverse osmosis (RO) and carbon block filter. RO is very effective but it is expensive and wastes water. Only 30-40% of the water that passes through the filtration system is actually used. Carbon block filters are a little less effective, but they are cheaper and less wasteful. Most nurseries use well water and/or a RO system. They realize how important good water is for their business. This is one reason why plants don’t thrive when you take them home.
YOUR WATER SOURCE
There are 3 main sources of water: reclaimed water, well water, and rain water. Reclaimed water is the worst for your plants. It contains less chlorides (salts) and dissolved solids but much higher chlorines. (There are no regulations on chlorines). Reclaimed water contains suspended solids that clog up filters. Murza recommends using a 5 Micron filter in front of a carbon filter.
Well water is a blessing and a curse. Inland well water can be excessively high in iron or other metals. Wells close to the bay or beach contains excessive salts. Each well is different, but at least you do not need to worry about chlorines.
Rainwater is the best source of water. It allows you to get full use out of your fertilizer, there are virtually no dissolved solids, picks up free nitrogen, and a pH of 6.9. Rainwater does require extra work to collect and utilize.
WHAT TO BUY
Gary recommends the garden hose filter from Pure Water Products. Follow the link. If you use city or well water you will need a single garden hose filter (part# gh101) and a Matrikx CTO Plus cartridge (carbon filter). If you use reclaimed water you will need a double garden hose filter (Part # gh103), a 5 Micron String Wound Sediment cartridge, and a Matrikx CTO Plus cartridge. The water will need to go through micron filter first to remove the suspended solids and keep them from clogging the carbon filter.
Many garden groups offer classes in making a rain barrel. If you are in Fort Myers you can purchase a rain barrel at Edison Gardens for $50.