On 5/20/2024 at 10:28 AM, Merlyn said:

I'd *guess* that the pH is high.  You could probably test the soil if you wanted to.  I'd do the boron treatment anyway.  It doesn't take a lot of uptake to fix a deficiency.  That's why palm fertilizers have a relatively low percentage, around 0.1% or so.

One thing you could consider is adding a thin layer of compost to the beds prior to mulching.  I probably wouldn't use the "Black Cow" stuff, as it is usually very dense and sludgy.  But I just used about 15 bags of generic box store "compost and manure" mix along with mulch in a bed of bamboo.  It's already partially decomposed, so theoretically it ought to decompose and provide organics to the soil faster than waiting a couple of years for mulch to decompose.  I know it works with sand soils, as they use it to "top coat" grass areas to help add organics faster.  I don't have any experience with adding sulfur or other acidifying stuff, as my soil is in the 6-6.5 range already.

Thanks! So something like this ? https://www.homedepot.com/p/1-cu-ft-Steer-Manure-Compost-Blend-Soil-Amendment-71751185/100619087

4 hours ago, gratkov said:

Thanks! So something like this ? https://www.homedepot.com/p/1-cu-ft-Steer-Manure-Compost-Blend-Soil-Amendment-71751185/100619087

Yeah, around here they have a "Timberline" brand that's composted forest products + cow manure.  I'd expect that any local source would be about the same.  A smallish amount of that spread around ought to decompose a lot quicker than doing 100% mulch.  I'd think that would help in a low rainfall area.  Here in the swampland of FL the problem is getting good enough drainage, because we have daily afternoon thunderstorms from mid May through October.  So I'm kind of SWAG'ing it here as to what might help retain water for your without becoming a muck layer.  Hopefully some AZ people can correct me if I'm way off base.   

Queen Palms are drama queens in the desert. 
if you do plan to replace them for Washingtonia palms, I would just go to the nursury and buy small size. Spend more for dates palms, Brahea palms.