So here we are at the tail end of our rainy season and it seems the precipitation fairies are seeking to get the most out of this season as they can. I simply can’t recall a recent wet season that has been as wet as the 2012 season has been. While this is good news for us with regard to our aquifers being adequately recharged, it makes for some challenging growing conditions for plants.
One of the biggest challenges I am currently observing is Iron Deficiency, particularly on those plants that are persnickety about pH. What I am seeing is a very particular pattern of yellowing of the leaves of affected plants.
Here are the characteristics of Iron Deficiency (anemia) on plants:
1. Yellowing occurs on theNEW GROWTH
2. Yellowing occurs in the tissue BETWEEN THE LEAF VEINS
3. The leaf VEINS are prominently GREEN against yellow tissue
4. Signs of secondary infection/disease may be present (eg. Black sooty mold).
Here’s a little background on Iron. Iron is an element critical to plants, although it is necessary in only small quantities in comparison to the quantities of N-P-K (Nitrogen, Phosphorous, and Potash (Potassium)) needed. It is this relatively small amount of Iron required that gets Iron and about 16 other nutrients the title “micro elements” , or formerly “minor elements” (or “minors” as you will hear the old timers refer to them). The micro levels of Iron are used by plants to make food (a process known as photosynthesis).
While there is more than one circumstance that will inhibit Iron absorption, there are several easily initiated cultural practices that will enhance iron uptake. Because Iron absorption is only possible in a very narrow range of slightly acidic pH conditions, the plants we commonly refer to as “acid-loving” are those most prone to falling out of Iron-prime pH range.
The cultural practice that corrects for this is to know your acid sensitive plants, and implement practices that affect a sustained acidic pH.
1. Amend beds with Marvin’s Magic Mix, with pH correcting Canadian peat
2. Apply Holly Tone to plantings of acid loving shrubs such as Ixora,Gardenia, Azalea, Ilex species and Hibiscus. This acidic organic fertilizer breaks down slowly to provide season-long pH suppression
3. Some ornamentals which are exhibiting signs of stress form prolonged anemia (black sooty mold) can benefit from the application of a granular systemic pesticide. This is the least toxic approach to conventional management
4. Mulch with pine straw. All parts of the Pinus spp are acidic in nature, so pine straw serves as an acidifying mulch that will decay in the course of a couple of seasons
The second dilemma in addressing Iron deficiency in the garden has to do with the manner in which Iron is absorbed by the roots of a plant. Taking up Iron is not an easy process, in fact it requires the plant to expend energy in two separate steps of modifying the iron molecule into a form that can move through the plants membranes (ie, be absorbed).
Utilizing the first step listed above results in a “chelated iron molecule”. If you facilitate one or both of these two steps through your gardening practices, you will minimize the energy expenditure on the part of the plant. What does that look like to you? Well, you won’t see the microscopic process, but conserved energy = increased resilience in any organism, and in your garden that means, more flower, fruit, foliage – more BLISS in general!
When soil becomes water logged, it is even more difficult for the plant to absorb iron that is the likely cause of the anemia currently occurring. How can one reduce energy expenditure in iron uptake? Correcting for wet soil can be achieved with planting at higher grades and adjusting irrigation for wet season, but even then we do occasional experience the “wetter-than-usual” wet season, and all my best plans . . . hmm, better not go there. Suffice it to say, all you can do is be mindful. Pay attention and you will catch the early signs, allowing you to apply the stitch in time to save yourself nine.
Another way to facilitate iron uptake is to introduce the beneficial microbe Streptomyces lydicus to your soil. This cousin to the bug that gives you strep throat, will do step one for the plant and is a powerful anti-fungal as well. S. lydicus is part of the “Magic” in Marvin’s Mix.
It is possible to grow your own beneficial microbes and build your own living soil through a composting effort*. A third approach, which may be the best option when you are seeing clear evidence of anemia, is to provide the plant with chelated iron in the form of a foliar spray. This method of iron delivery results in the plant absorbing the Iron right through the surface of its leaves– the equivalent of an IV infusion of much needed iron.
Our professional sales staff can show you an easy method of hose-end delivery that will prove valuable for many other garden interventions. If you also apply some Holly Tone, you will correct the issue immediately and prevent long-term problems.
To get yourself ahead of the curve for next year, mark your May 2013 calendar now with a reminder to apply some Iron Tone to your garden once the rains start to come. This new product from the Espoma family provides a steady supply of iron and sulfur to hold the pH in a desirable range, giving you wet season-long coverage without breaching the Martin County fertilizer ordinance blackout period. It’s particularly helpful in keeping your fruit tree yields high.
So do yourself a favor and scout your garden for anemia this week, keeping an eye peeled for this problem through the end of the rainy season and paying special attention to your “acid-loving” plants. Bring in an anemic leaf and save 10% on your purchase of any Espoma, Bonide, Southern Ag or Fertilome product to correct your problem.
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Practical Take-home Lessons
Excerpted from Iron (Fe) Nutrition of Plants by George Hochmuth
• Iron is a required plant nutrient for normal plant growth and reproduction
• Iron is required in small amounts and is called a “micro nutrient.”
• Iron is a challenging plant nutrient to work with because of its reactions in the soil and its plant physiology.
• Soil testing for Fe is problematic and there is no single superior procedure.
• Iron deficiency shows up as chlorosis (yellowing) in the newest plant growth because Fe is not re-mobilized in the plant from old to new leaves.
• The easiest and most effective strategy to temporarily correct Fe deficiency is with foliar sprays.