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19566Re: [AZ] this is from the ASK US page, so please send me a CC

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  • George Klump
    Mar 23, 2014
      23 March 2014

      Hi, Liz,

      Having lived in Dallas for many years, I can understand your frustration with the soil and the advice you've been given. 

      First, aluminum sulfate is completely inappropriate for the soil, as you have found out.  They may have meant ammonium sulfate.  But no matter now, the damage has been done.  Just plain soil sulfur is far better.  While it's a tad slower, it will last much longer than most other methods of acidifying the soil there.  

      Second, none of the soil in the Dallas area is notable for anything.  For the most part it is a rather heavy clay and azaleas do not get along with it as a rule.  Since azalea roots will move out horizontally from the plant rather than vertically down into the ground, there are two things I would suggest.  1] I would dig them up gently and make sure that the hole is wide enough meaning that, if the root ball was maybe 6-inches in diameter, I would make the hole at least 12-inches in diameter.  18-inches would be even better.  2] I would get myself some COARSE peat moss, the chunky kind sometimes sold under the name of spaghnum plus some perlite and shredded bark.  Those three items can be physically mixed together in equal parts, i.e. 1 - 1 - 1.  Eye-balling will work. 

      Third, I would take the mixture and fill the hole probably two-thirds of the way and, then, take the hose and soak it until the mixture becomes a "soup".  At the same time I would have a few bags of gypsum handy [calcium sulfate]: they're cheap.  The gypsum I would mix into the hole liberally and, then, after you have all your azaleas fixed nicely, broadcast the gypsum liberally over all of the soil and include your lawn.  While the water is percolating down into the hole, take your azalea and with the hose blow off most of the dirt from the roots, say, maybe 60% - 70% of the dirt.  Set the azalea back down on top of the wet mixture and fill the hole the rest of the way with the mixture up to about an inch below the plant's crown.  Then, water the entire thing the same way, i.e. soak it thoroughly and, then, walk away. 

      As for feeding, I find that azaleas do not like to be fed very much.  So we've developed a schedule which seems to work quite well for our plants: Easter, Fourth of July and Labor Day.  Those are easy dates to remember.  I use cottonseed meal because 1] it's inexpensive and 2] it's a very slow release and won't burn your azaleas.  Just a cupful around each plant watered in gently should do the trick.  

      Permit me a few comments on the gypsum because you are probably wondering how this came up.  The general soil of Texas from about College Station north is clay to a greater or lesser extent.  It's heavy and oxygen and air cannot penetrate it.  That being so, the tiny feeder roots of the azaleas will not penetrate it at all and neither will water which will just run off to some other place.  So you have a problem here: no oxygen can get to the root zone, no water can get to the root zone and the roots cannot penetrate the heavy clay soil.  Therefore gypsum to the rescue.  It will break up the soil to which it is applied in about one week.  [Just water it in gently.]  Then, your water will penetrate down to the root zone as will oxygen.  That will also encourage the growth of favorable soil bacteria which will help feed the little roots which feed the azalea.  I would suggest you apply the gypsum maybe twice annually, say, spring and autumn.  You will find that you will be using less water to accomplish the same purpose.  I know from long experience there that the sun and the heat associated with the weather from about late April to Halloween can be very intense.  Gypsum will ultimately save your water bill, if applied to the soil properly.  Gypsum will not change the pH of your soil which is probably 7.0 or slightly higher, but the coarse peat moss will certainly help the azaleas in that regard.

      It used to be that one of the finest nurseries around Dallas for azaleas was Northaven Gardens up on Northaven Road west of Central Expressway.  Last I heard, they were still going. 

      Good luck.  I hope you can still save your azaleas.

      George E. Klump
      Southern California Chapter, ARS/ASA       

      On 3/23/2014 6:20 AM, Liz Fitch wrote:
      [AZ] this is from the ASK US page, so please send me a CC
      "Liz Fitch" <liz@...>
      3/23/2014 6:18 AM


      Dear Sir/ Madam,


      I live in Dallas TX and have planted many azaleas over the last couple of years.  I have had the soil double dug using a soil designed for planting azaleas.  We had a late freeze and the leaves are turning brown and falling off.  After measuring the PH in my soil, which measured 7 I was told by a local nursery to use  Aluminum Sulfate to lower my PH levels.  My azaleas look worse than ever after applying the aluminum sulfate. I am just learning that Aluminum Sulfate poisons Azaleas.  Is there anything I can do to reverse Aluminum Sulfate damage?


      I anxiously await your response.






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