Soluble Salts On Houseplants Still A Problem

When Spring arrives trucks begin moving plants north to local garden centers and nurseries. In about a month we begin to receive a lot of the same questions dealing with plant care and go something like this.

“I bought a plant about a month ago, brought it home, watered and fertilized it, once a week. It’s losing leaves like crazy or the leaves are turning brown. What’s wrong?”

So we’ll try to get a jump on the questions, and hopefully prevent some leaf drop, brown leaves and plant frustration.



This article is from Dr. Joe Cialone… a friend, grower, Doctor, member of the Foliage Hall of Fame, plant pioneer, former Nurserymen and Grower Association President, and a great guy.

Dr. Joe is well known throughout the interior plant industry. His company, Tropical Ornamentals (TO) pioneered growing Aglaonemas in large containers in the 1970’s (changing their use indoors). In the 1980’s TO introduced Aglaonema B.J. Freeman, and brought new Aglaonema varieties “Jewel of India” and “Emerald Star” to market. In the 1990’s Joe formed Tropical Computers.

Tropical Computers provides digital plant images for interiorscapers. These images allow interior designers to produce a “finished” interiorscape design for client approval before ordering one plant. They also produce some great reference material every nursery, garden center, and public library should have. I could go on and on but I’ll let Dr Joe take it from here.

One of the most common problems affecting a plant’s life-span in interiors is high soluble salts. High salts are probably the most common cause of plant replacement, second to over-watering. Different plant species have differing tolerances to high salts; some plants can live in or around salt water.

Soluble-Salt Injury Symptoms

The symptoms of soluble-salt injury are often similar to those of having a plant too dry. Some plant species will actually wilt, and careful examination will show that they have little or no root system left. Gray-green leaf color and tip and lateral- edge burn are also typical symptoms.

If plants decline rapidly in the time period following fertilizer application, it is a good bet that the plant is suffering from salt toxicity. The application of chemical fertilizer is the most common source of toxic salt levels in interiorscape plants.

Sometimes the fertilizer has come with the plant when it arrives from the grower. It is very important to remove any surface fertilizer when plant shipments are received from any grower. Most growers for the interior market are aware of the potential problems and use fertilization programs that avoid the high- salts problem. Slow-release fertilizers and the liquid application of nutrients are two methods growers use to control salt levels during the growing cycle.

Long-term, slow-release fertilizers incorporated into the soil usually do not cause problems, but short-term, quick-release fertilizers can pose a serious threat. Be alert to the difference in the looks of the various kinds of fertilizer that come with your plants. Nutricote (light-gray prills) and Osmocote (yellow-orange prills) are the most common forms of slow-release food.

Quick Release Foods

The quicker-release foods tend to be made with several different rock-like materials of differing sizes and colors, often containing white, red or blue materials. Remove any loose fertilizer material on the soil surface of your plants.

The problem of high salts is accentuated when plants are used indoors because water levels are usually reduced under low light conditions. Actual salt concentrations are a function of the amount of water present. A given amount of salts in a large amount of water will create a low salt concentration. The same amount of salt in a small amount of water will yield a high salt concentration.

Because the salts are soluble in water, they can be leached out of the pot by applying water and allowing it to drain out of the bottom.

The purchase a salt meter measuring soluble salts is one of the few things in plant care that we can measure objectively. The procedure for the objective measurement of salts is quick, and can be done out in the field. There are many salt meters available on the market that are battery-operated and portable.

There are critical salt levels that most plants do not like. In addition to detecting high salt levels, the meter can be invaluable in telling the status of your in-house nutrition programs. Spot-checking plants or planter beds can tell you whether your salt levels are trending up or down.

The purchase of a salt meter, combined with purchasing your plants from quality growers, will be one of the best plant investments you can make.

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