Last year at TPIE, it was my supreme goal to find a "the best possible" potassium supplement to fix that darn potassium spotting so prevelant in adonidias in particular. After a lot of fervent research and thanks to some reknowned brains that I picked (particularly Dr. Chen of MREC, Lynn Griffith of A+L Southern laboratories, and, of course, my mentor David Liu) I may have a surprise answer. There has been much discussion over the course of several threads of the cause of certain leaf spots, particularly fluorosis. I mention this because as it turns out, the two disorders may be closely related and likely have nothing to do with deficiencies or the level of fluorine or chlorine in the water. The verdict.... and let me digress for just a moment..... Have you ever taken over an account with a jc or a cane with horrible yellow spots and "grown it out?" I.E., have you ever had the new foliage grow out perfectly normal with no spotting whatsoever in spite of using the exact same water source the previous company used? In that case, we all know too well how pre-existing material was likely severely underwatered by the prior company. Not to mention that its my personal experience that techs in general tend to be too conservative with their irrigation approach to dracaena (as I have said to many a tech.- its NOT a cactus.) The verdict is simply dehydration. What does that have to do with Potassium deficiency? Well, let’s begin with some leaf analysis David Liu requisitioned in which symptomatic adonidia leaves were not deficient in potassium. Next came a conversation with Dr. Chen in which he suspected the role of reduced humidity in the interiorscape environment as a major source of potassium spotting. Add to that an article that Mr. Griffith brought to my attention which outlines how dehydration causes fluorocetic acid to build up in plant stomae (which in turn freezes the stomae open and they then "burn.") The final piece of the puzzle is that the two elements that regulate the opening and closing of stomae are potassium and chlorine/fluorine. Therefore, were there an actual excess of chlorine or fluorine in plant tissue it would appear exactly the same as the effects of dehydration because chemically the result of both afflictions in the stomae is the same regardless. Similarly, the burning/dehydration of stomae in Adonidias would appear exactly the same as if there were an actual potassium deficiency because potassium is critical to plant functions within stomae specifically. I can also vouch for first hand observations of tech. mistakes and competitor accounts that Adonidia dehydration and "potassium spotting" go hand in hand.

The reason that I bring all of this technical junk to your attention is because I see this type of spotting very often in adonidias industry-wide. Here are a few tips on how to prevent it as the yellow spots cannot be corrected.

1. The period immediately after install is very critical. Be sure to irrigate/check new specimen material 2-3 times a week for the first month or more as needed.
2. Some spotting may be inevitable, probably due to reduced humidity in the interiorscape setting.
3. Be certain technicians recognize the importance of probing into the rootball versus the surrounding soil if the plant was up-potted.
4. Water will sometimes roll off a dry rootball and get absorbed into the surrounding soil. Try making a "moat" by piling up the surrounding soil into a ring around the rootball so the the water is trapped and absorbs slowly into the rootball.
5. Closely moniter the soluable salt level of specimen/new material. Soils with elevated salts will cause dehydration regardless of the moisture level of the soil.

Good stuff, Lynnae. The point you made about the "moat" technique deserves some expansion. The issue of media incompatibility in interiorscape applications may have a lot more impact on the performance of our interior plants than most of us think. Read almost any book on caring for indoor plants, and you will note that the authors invariably raise a caution flag about using potting media that are close in structure and composition to the "native" medium in which the original rootball of the plant was grown. That is, try to duplicate the nursery mix closely, unless you are willing to completely strip away that medium and repot the bare-root plant in a different medium altogether.

Very often, we receive specimen plants from the nursery that have been grown in some sort of field soil for the early portion of their lives. This soil, especially from Florida, is predominantly sand with some organic matter mixed in. To try to duplicate this medium when up-potting such a plant for the interiorscape is difficult and probably not advisable for the plant’s sake. Sandy soils are notoriously difficult to irrigate properly indoors, tending to shed water and allow it to permeate only unevenly throughout the rootball. They are also somewhat more difficult to assess for moisture levels due to their weight, which makes the "heft-and-estimate" method useless, and renders various types of moisture meters ineffective as well.

When trying to match a "native" container medium for repotting purposes, structure is important for two reasons: first, moisture relations...a quick-draining native mix surrounded by a very organic, moisture-retentive mix will produce an incompatible interface between the two...the surrounding soil may stay constantly saturated, while the native soil is in a droughtlike state. Roots will fail to expand into the surrounding boggy soil in many cases, and the plant may fail altogether as roots rot at the wet interface. Second, aeration is obviously compromised when root systems that are acclimated to fast-draining media are confronted with heavy, organic, water-holding media surrounding them. Again, this will have a huge negative impact on most plants’ water relations, poor root aeration with increased susceptibility to root pathogens, and nutrient deficiencies exacerbated by lack of oxygen at the root zone and soil pH problems related to the incompatible media.

We need to look at plant cultural problems holistically, as Lynnae has so carefully explained in her case study. Americans, conditioned by our medical care system’s cause/effect, symptom/treatment mindset, tend to see things in black and white terms, believing that a symptom indicates the need for a "magic bullet" treatment for a single causative agent. In many cases, plant health problems result from a complex of causes, each with its own required course of treatment. We tend to blame the manufacturers of fertilizers, potting media, pesticides, etc. for our failure to recognize that many cultural problems don’t have a simple, one-shot solution. The patient often succumbs because of our naive belief in such simplistic solutions to what are multi-layered cultural deficiencies. We need to teach ourselves to think critically and logically about the patient as a whole, instead of worrying ourselves sick about a glaring symptom or two.

Clem