Hydroponic houseplant how-to part 2

LAST WEEK I DEscribed how to grow houseplants hydroponically, with plant roots either in aerated, nutrient-enriched water, or in some inert solid medium, such as gravel or vermiculite, which is periodically flushed with nutrient solution. Once a hydroponicum is operating, you can watch plants respond as you make adjustments in the nutrient solution. (I love that word “hydroponicum,” which I am borrowing from a text written by an Englishman promoting hydroponics in India in a book from about 50 years ago). Try a bit more nitrogen in the nutrient solution to “green up” the leaves, or a bit less to make growth less succulent. Yellow patches on young leaves? Add more iron. Watching a plant respond to your care is one of the joys of gardening.

But why would the farmer who grew the hydroponic tomatoes I examined in the grocery store last week want to grow plants hydroponically? What could be the attraction, given that real soil is a renewable, natural resource that has done a good job of supporting plant life for eons?

One reason for commercial hydroponics is to avoid pests, which are a threat especially to greenhouse growers. Theoretically, if a greenhouse grower started with “clean” plants growing in an inert, sterile medium like gravel, then fed the plants an inert, sterile nutrient solution, there would be no pests to plague plants.

Problems arise when a disease spore happens to waft into a hydroponic greenhouse. The nutrient solution sloshing from one plant to the next is very effective at spreading pests once one plant is infected. And in the absence of beneficial insects or microorganisms, which are present under natural conditions, any pest that gains a foothold can multiply unchecked.

The claim is made that hydroponic plants yield more than plants growing in real soil. Present claims are nowhere near as extravagent as when hydroponics was first developed. That was in 1929, and the “inventor” was professor W.F. Gericke of the University of California. Newspapers hailed hydroponics as the greatest invention of the century, and predicted were that farmland soon would become a relic of the past.

Now such claims are tempered. But still, that displaced Englishman, the hydroponicist mentioned earlier, presents a table in his book showing that hydroponically grown tomatoes, beets, corn, even rice and wheat, have the potential to outyield their conventionally-grown counterparts by more than ten-fold. I contend that if the same care was lavished on conventional plants as on hydroponic plants, discrepancies would vanish. Also, yield is not the only consideration in growing plants. Nutritional quality and plant health also are important, and not always directly related to yield.

Hydroponics does make it feasible to grow plants where there is no soil. During World ganisms, as mentioned previously, gobble up plant pests. Others chew up dead leaves, stems and roots of plants, and dead animals, in so doing recycling nutrients for use by living plants. Still others use their long, thin, thread-like bodies to gather nutrients for plants from the far-reaches of the soil. And some actually gather elements from the air, and turn them into fertilizer for plants. All these organisms also produce hormones, antibiotics, and chelators, which are not nutrients, but do affect plant growth and health.

Nothing like this goes on beneath a hydroponically grown plant. Hydroponic plants get only the thirteen nutrients deemed essential for their growth, and all nutrition comes from chemicals dissolved in water. The hydroponic farmer has to go out and buy these chemicals, along with pumps and tanks and timers, and electricity to run the pumps and timers. Consequently, hydroponics can be very costly to install and to run.

War II, fresh vegetables for American GIs were raised in this manner on nonarable islands in the Pacific.

But real soil, wherever it exists, can nourish plants naturally. Every teaspoon of soil contains billions of microorganisms that contribute to the well-being of plants. Some microor-

Hydroponics does have the advantage — or is it a disadvantage? — of being amenable to automation. Once a grower has a system perfected for a particular crop, all that is needed is someone to stare at some dials to make sure everything keeps operating smoothly. But that can present a problem. A greenhouse trade journal once reported that staring at dials becomes too boring for employees — not nearly as satisfying as mixing up a batch of potting soil or probing the soil with your finger to see if a pot needs water.

Any gardening questions?

Email them to me at garden@leereich.com and I’ll try answering them directly or in this column. Come visit my garden at www.leereich. com/blog.

Don and Dave Runyan | Project of the Week