11/12/2012 - By Marshall Horsman

Zinc. Yes, zinc is this month's nutrient of the month. I contemplated skipping it and going straight to boron. I mean, when was the last time a client accused our fertilizer of not having enough zinc? And what does a zinc deficiency look like? Well, after doing a little research on zinc, one of our plants’ essential micronutrients, I find it does indeed have its purpose and worthiness to make this month’s newsletter.

Like copper, zinc is a metal needed in very low quantities. Sandy, inorganic soils can be low in zinc and high pH soils can lock it up. It does several things physiologically in plants including acting as a metal component of enzymes for protein synthesis, which in layman’s terms, helps in energy production. It is an important component of the plant hormone auxin and various pigments. Zinc also helps plants assimilate or "get ready" for cold weather.

Plants deficient in zinc can develop a symptom called "small leaf" or rosetting of plant terminals, similar to a witch's broom, as internodes are compromised in its absence. In agriculture it is known that zinc deficient fruit orchards will have a lower yield. In tuberous crops like potatoes and turnips, reduction in tuber yield is also an issue.

Aside from galvanizing "tin roofs" in third world countries, zinc has been proven to play a large role for humans. Regarding health, much of our zinc is gained by eating fruits and vegetables. Some old timer palm growers swore that adding zinc sulfate to their nutritional sprays helped leaf expansion and color especially when areca palms were more widely grown.

Ornamental plants do not need a lot but they do need some. So having around .07 to .10 zinc percentage-wise would be good. Some of our business crosses over to citrus, blueberries and other agronomic venues. Zinc fertility would be something to not skip over. Pollen grains are very high in zinc, so flower fertilization for fruits is greatly improved with adequate zinc fertility. Soil analysis showing 5-15 ppm zinc is normally adequate. Plants also get zinc from mancozeb or Dithane sprays.

On the flip side, too much zinc can be a problem, so when going over a leaf analysis, keep an eye on zinc levels. Orchids and Hibiscus are notorious for accumulating zinc but they seem to tolerate it. Bromeliads are sensitive to it. Run off of rain from galvanized gutters or roofs have even contributed to zinc toxicity. So there you have it. Everything you wanted to know about zinc but were afraid to ask.