The Huntsville Item, Huntsville, TX


June 1, 2014

Master Gardeners: High salt levels not good for most plants

HUNTSVILLE — “Water, water everywhere!  And not a drop to drink!”

Paraphrased from “The Rime of the Ancient Mariner,” Samuel Taylor Coleridge, 1834. The setting? A sailor surrounded by salt water that he cannot drink.

We know that people die of thirst in boats adrift in an ocean of salt water.  We know that plants not adapted to living in salt water — or soil with a high salt content — can die from too much salt.  We know that land animals and birds generally won’t fare better than humans in those environs.

But how do many seabirds do it?  Birds such as albatrosses, petrels, shearwaters, pelicans, and those dear high-flyers who drop stuff on you from the sky at the coast – seagulls.  Some spend months and even years at sea soaring over the world’s oceans without ever approaching any land mass. 

So the question arises, “What do seabirds drink?” The answer? Seawater. The next question naturally is, “How then do they survive?”

Seawater has a much higher concentration of salt than that found in the body fluids of most animals including mammals and birds. Therefore, when seawater is ingested, the osmotic balance of these animals is upset. Mammalian kidneys, in order to flush the body of excess salt, must use one and a half times as much fresh water as the amount of ingested seawater.

Without fresh water, dehydration of body tissues ensues and, in most cases, death follows. Avian kidneys, being much less efficient than mammalian kidneys, must use an even greater amount of fresh water to rid the body of seawater. Thus, seabirds would encounter the same fate if they had to rely solely on their kidneys to maintain their body’s osmotic balance.

But seabirds have their own desalinization systems to deal with excess salt taken in by drinking seawater and feeding in the ocean. The salt they take in is absorbed and moves through their blood stream into a pair of salt glands above their eyes. The densely salty fluid is excreted from the nostrils and runs down grooves in the bill. As the drop gets larger, the bird shakes its head to send the salt back to the ocean.

Meanwhile, what about life a distance from the coast, say, in Walker County?  

Some of us have whole-house, water-softening systems.  We connect the outdoor sprinkling system to incoming water before it reaches the softener, where sodium is added in exchange for other hard water ions. 

What about tap water? Some install special equipment to reduce the salt content. Other authorities advise that unless persons with coronary conditions will be drinking it, the limited quantities present should not be a problem. Some just want to justify buying and drinking bottled water. Others point out studies showing tap water generally is as safe as any sold in bottles.

Some house plants and landscaping choices tolerate or even thrive in salty soil.  Though not all are well-suited to this particular climate for other factors, trees which well-tolerate salty soil include Thornless Honeylocust, Southern Magnolia, Willow Oak, Live Oak, Redbay, and Devilwood.

These shrubs are ideal for gardening with salty conditions:  century plant, dwarf yupon holly, oleander, New Zealand flax, rugosa rose, rosemary, butcher’s broom, and yucca.  Same story with perennial plants:  daylily, lantana, prickly pear cactus, and lavender cotton. Also moderately tolerant:  yarrow, hardy ice plant, dianthus, Mexican heather, crinum lily, mallow, hen and chicks, and hummingbird plant.

Among vegetables, those with high tolerance for salt: beets, kale, asparagus, spinach.  Those with moderate tolerance: tomato, broccoli, cabbage, pepper, lettuce, corn, potato, carrot, onion pea, squash, cucumber.  And those with low salt tolerance:  radish, celery, beans.

In order to help avoid problems: provide adequate drainage, choose salt-tolerant plants, maintain adequate soil moisture, avoid watering too often, use low-salt content organic matter such as peat and compost, and submit soil tests to determine whether other treatments are needed.

Of course it never hurts to experiment.  You may want to fill a wash tub with soil typical of the garden area, install an olla (large clay pot to be kept filled with water, which will seep into the surrounding soil), and try several types of plants which you hope to use in the larger setting.

This will identify approaches for your special place, which keep salt levels appropriate for what you hope to grow while avoiding wasting water — another good practice consistent with LEAF-PRO principles and being earth-kind!

So whether it’s you or your plants which are drinking water — you may pass the salt — or maybe not!

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