In our ongoing look at the health of plants and their surrounding medium, and for our ongoing fun in using dietary analogies, today we look at the detrimental effects of too much salt in the soil of potted plants. Overly high salinity leads to the burning of roots and leaves and inhibits a plant’s ability to absorb water. For this reason, we need to be careful not to add to many inputs i.e. fertilizers, vitamins and mineral supplements. Each of these will increase soil salinity. In addition, we need to take into account the salts from minerals that can be present in the water used for irrigation. The harder the water the higher the mineral content, and the higher the mineral content the higher the chance of increasing soil salinity. Be equally mindful of softened water as the agent for removing minerals is salt-based. This is the reason many gardeners choose to use filtered water that has gone through reverse osmosis or distilled water.
It is crucial to feed potted plants as they are completely dependent upon the gardener. But too frequent feedings can quickly lead to high soil salinity which can then lead to high acidity and nutrient lockout. High salinity can also result from too infrequent watering which does not allow the salts to percolate below the root zone. In time, all added inputs will infiltrate through the soil and ultimately be leached out but the salt is often left behind.
Now, how can you be sure that you’re dealing with high soil salinity? Well, short of sending it away for analysis, you could purchase a salt meter, though keep in mind that they can be pricey and prices can vary widely so please do your homework. Other than that all that can be done is to look out for any signs such as a white crust that can form at the surface or the burning of young leaves.
A method for treating soil salinity in potted plants is to flush with filtered water periodically. Flush anywhere from a couple of days to a couple of weeks depending on the severity of salt build up. The addition of a wetting agent can also be applied to expedite the process, but these should be used sparingly. If soil salinity becomes a persistent problem, it may be more efficient to repot. It may also be time to cut back on the use of fertilizers, manures and sludges and to incorporate more products that are not petroleum-based.
A customer recently shared their fertilizer recipe for their prized Hofstras which is completely petroleum-free. It consisted of Alaskan Fish fertilizer, liquid Hormex Growth Stimulant and a compost tea. Now that is a potent combo. The fish adds nitrogen to fuel cellular functions while the Hormex stimulates root growth and the compost tea adds beneficial bacteria to regulate the environment of the expanded root zone.
However, as with all recipes, it ultimately comes down to preference and finding what works for you on a consistent basis. Just hold the salt!