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Speckled Rhodie Leaves
In article , "Anonny Moose"
wrote: A few of my rhododendrons' leaves are showing a loss of color this winter. They look almost white with green speckling. Anyone know what this is and what I can do for it? Thanks. Karen portland, or When SPOTS appear on leaves in winter, it can be any number of problems causing ill health to the root system -- such as borers or fungus -- & winter spottiness is just the first sign of worse to come. But if the whole leaf is just fading to yellow between the leaf-veins, the shrub is chlorotic, which is repairable. This happens to all plants that prefer acidic soil that end up in poor or alkaline soil. Some people induce the problem if they add fireplace ashes to gardens, believing this is beneficial when it can be very harmful to rhodies, roses, blueberries, apple & cherry trees, by alkalinizing soil. If you've gone the "ashes are good" route then you've injured the soil for rhodies. If that is the case, rain & waterings will eventually wash out the alkalinity, unless your local soils are naturally alkaline, then it's going to be a recurring harrassment to ammend soils to acidic conditions unnatural for your area. Over fertilizing or the wrong fertilizer can also cause chlorotic conditions by interferring with rhodies' capacity to take in iron. Heavy feeding of phosphorus intefers with iron uptake even if the iron quantity in the soil is sufficient. Run-off from newly laid concrete or cement, OR unstable deteriorating old cement, can alkalinize the immediate area (stable well-cured cement is NOT a problem though). If you lime a nearby lawn, this can leech into areas of woody shrubs, damaging the soil for many perennials & shrubs & fruit trees -- what's good for lawns is not always good for much else, so take care not to lime lawns too near gardened areas. The usual "fix" is sulfer or iron sulfate. This assumes the soil does have iron in it but that alkalinity or other factor hinders uptake of iron. A mere tablespoon of sulfer in the soil around the base of each shrub will help it take in the iron it needs. If there's something continuously keeping the area to the alkaline side of the pH scale, it will need a tiny bit of sulfer EVERY spring. But this is a compensating method, not a real restoration if the soil has been alkalinized. A great amount of peat worked into the soil & heavy topcoatings of leafmold & composted manure will help acidify the soil itself & increase plant health. Be VERY careful with fertilizers that shoudl be low in nitrogen & low in phosphorus; until alkalinity can be reduced, no amount of even a properly balanced rhody/azalea fertilizer will help, because the problem is that the shrub cannot take in iron when soil is limey. Very rarely excessively acidic soil is the culprit, as even acid-loving plants such as rhodies want only moderate acidity. In such a case a little lime actually helps rather than increases the problem. So you need to know your specific pH conditions before knowing which action to take, as lime will increase the problem if the soil is alkaline, & help the problem if the soil is super-acidic. Though naturally alkaline soil or soil damaged by excesses of phosphorus or lime or ashes are commonest culptrits, sometimes the soil is fine & some other thing causes chlorosis, but the other causes would usually mean the shrub did not do well for a few years before began to show stress, but always struggled in the given location. Compacted, poorly draining, clayey, over wet soil destroys a rhody's capacity to take in iron, as does being planted too deep (their roots must remain "in the shallow." These conditions usually cause root stress & disease or attract insect damage the first sign of which will be either winter spottiness OR chlorosis. A greater amount of peat or other organic material in the ENTIRE garden, well-loosened for better aeration. If soil is literally iron deficient or magnesium depleted, this can be narrowly resotred. A feeding of liquid chelated iron according to product directions will be the proper fix or iron deficiency. For magnesium depletion, a high-magnesium low-nitrogen evergreen fertilizer, or just epsom salts (magnesium sulfate) will fix that. Some recommend a combination chelated iron with magnesium sulfate together as kind of broad-spectrum approach. But tinkering with soil chemistry repeatedly will in the long run do more harm than good & the original cause of the problem should not be permitted to continue, so that organically rich slightly acidic soils remain in prime condition by means of healthful annual topcoatings of leafmold or manure compost. Without knowing the soil conditions beforehand, & without knowing why the soil went wonky if it was previously just fine, any action you take could turn out to be wrong. You'll know fast if the action you take was helpful, as it takes only about two weeks to begin turning back to green. -paghat the ratgirl -- "Of what are you afraid, my child?" inquired the kindly teacher. "Oh, sir! The flowers, they are wild," replied the timid creature. -from Peter Newell's "Wild Flowers" See the Garden of Paghat the Ratgirl: http://www.paghat.com/ |
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