[Arid_gardener] Oleander Question

Fri May 18 10:21:16 MST 2007

You have mature plants with a lot of foliage transpiring moisture continuously.  If the feeder roots can't keep up with transpiration, wilt occurs and if water is not replenished the wilt will reach a critical stage when foliage drops.  Keep in mind, however, that all healthy plants shed, plants under stress from disease, lack of water or fertilizer shed more. 

The most common problem I have seen in this climate is watering too shallow. I irrigate citrus by filling a shallow three or four foot wide trench centered at the drip line with about a half inch head of water that I adjust the hose to maintain until I can easily sink a 1/4th inch brass rod 36 inches long with a home-made handle to the hilt in several places around the drip line. When I scratch about 3 inches in the trench at the drip line and find it quite dry I repeat the process regardless of how long it had been since the last irrigation.

Plants struggle in sheer desparation in this climate with shallow irrigation regardless of how often you water. If irrigation is deep, the roots follow but they will not pennetrate dry soil. A deep or extensive rooted bush or tree has a much greater resistance to drought. To reiterate, Oleanders have an extensive root system and a huge vegetative mass that I envision will transpire an emense volume of water. If the roots can't keep up, guess what happens? The leaf cells collapse and the leaf falls.

Another problem with irrigation methods is applying water too close to the stem keeping the root system tangled in a tight circle where it hasn't the feeder-root capacity to keep the growing upper structure and its foliage turgid.

Dick Gross, Master Gardener Volunteer
U of A Maricopa County Cooperative Extension

---- Original Message ----- 
From: "BRIAN SYLVESTER" <briansylvester at msn.com>
To: <rkgross3 at cox.net>
Sent: Friday, May 18, 2007 7:54 AM
Subject: Re: [Arid_gardener] Oleander Question

> Thank you Dick for the prompt reponse but I can assure you it is not due to 
> over watering.  We rarely water the plants with the soaker hose just every 
> once in awhile. Maybe once a month.  It this enough or should we be doing it 
> more often?  What about the type of fert. to use and should we consider 
> Ironite to solve the yellowing problem?  Thanks Brian.
> 
> 
>>From: "Dick Gross" <rkgross3 at cox.net>
>>To: "L V" 
>><fitnessgirlaz at hotmail.com>,<briansylvester at msn.com>,<arid_gardener at Ag.arizona.edu>
>>Subject: Re: [Arid_gardener] Oleander Question
>>Date: Thu, 17 May 2007 09:40:50 -0700
>>
>>This analogy is what I have believed for years, Brian. If anyone has a 
>>fifferent take on the situation, I would appreciate hearing it and will 
>>stand corrected.
>>
>>An excess of water and/or fertilizer will result in lush vegetative growth 
>>at the expense of flowers that a plant produces when percieving that its 
>>existence is in jeopardy causing an urgent need to produce progeny. A plant 
>>exploding in new vegetative growth is fat and happy seeing no need to 
>>reproduce by producing flowers, the only reason for blooming that attracts 
>>insects who move pollen around to complete a sexual union producing seed.
>>
>>In this climate, the two most important culture factors may be deep 
>>irrigation while flushing salts from the root zone but roots die 
>>immediately without the air that flows in behind the water table as it 
>>travels downward. Deep irrigation results in deep roots that can better 
>>sustain the plant during drought. Shallow roots run out of water quickly. 
>>Watch for a slight wilt, the earliest sign of water need. But, when the 
>>root zone stays saturated and root hairs strangle without air, they quickly 
>>die and you will hear a choking, gagging sound if you hold an ear close to 
>>the ground.
>>
>>Dick Gross, Master Gardener Volunteer
>>University of Arizona Maricopa County
>>Cooperative Extension
>>
>>----- Original Message ----- From: "L V" <fitnessgirlaz at hotmail.com>
>>To: <briansylvester at msn.com>; <arid_gardener at Ag.arizona.edu>
>>Sent: Wednesday, May 16, 2007 5:32 PM
>>Subject: RE: [Arid_gardener] Oleander Question
>>
>>
>>I have had the same problem and it was because of over watering.
>>
>>
>>>From: "BRIAN SYLVESTER" <briansylvester at msn.com>
>>>To: arid_gardener at Ag.arizona.edu
>>>Subject: [Arid_gardener] Oleander Question
>>>Date: Wed, 16 May 2007 16:02:16 -0700
>>>
>>>I have the following problem with my oleanders and was wondering if it is 
>>>normal or is there something that I can do to prevent it.  Here is the 
>>>situation:  Everytime this year we have yellowing of the leaves followed 
>>>by leaf drop on our oleanders.  We have about 8 plants that are about 14 
>>>yrs old that are on the west side of our house.  I also noticed that they 
>>>don't bloom as much as ones that I see around town.  Is there something 
>>>that I can be doing different?  Should I try Ironite on the plants in 
>>>early April? Thank you for your time on this matter.
>>>Sincerely,
>>>Brian G. Sylvester
>>>
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> 
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