[Arid_gardener] pin cushion cactus turning yellow

[Janet Howe]

Original question:

Please let me know why  some of my pin cushion cactus are turning yellow
& some stay green.. To much water or not enough? And I have another that
is paleing & shrivaling. Is that to little water?
annsdogtraining at dc.rr.com 

Answer:

Ann, you don't mention what sun exposure your cactus are getting, but I
would venture to guess that some of your cactus get more sun than
others. I have noticed some of my cactus are getting sun burned,
partially because of the extra hot temperatures of late, but also
because some just aren't getting enough shade.  Although at first glance
one would think cactus could take direct, burning sun all day long,
that's really not the case.  In the wild, they usually are strategically
placed near a tree, shrub or other object that will shade them for a
portion of the day.  Try putting some shade cloth over the ones that are
turning yellow, at least until the temperatures lessen in the fall.  

Water is also important, the one you say is paling and shriveling,
probably does need more water.  Cactus need to be deeply watered --
enough water to dampen the soil at least a foot deep (you can use a
probe -- push it into the soil until the probe stops -- where it stops
tells you how deep the water has penetrated).  How often depends upon
the type of soil and whether or not you have an established plant (once
established, they can do pretty well on their own unless you get an
especially dry and hot year like we had up until recently, then they
could use a drink or two).  I suggest deep watering(and maybe cover with
shade clothe till fall to give it a break) the pin cushion  that is
paling & shriveling and see if there is improvement.  If it's not too
far gone, it should recover, cactus are very tough characters!

Good luck with your cactus.

Janet Howe
Master Gardener volunteer
Maricopa County Cooperative Extension