Question
Thank you for getting back to me so quickly.  I'll change  the watering schedule right away.

One follow-up question.  When you say to water "a lot longer" than 5 minutes, do you mean 15 minutes?  20 minutes?  And, should I use a watering hose?  Or re-set the sprinklers along the drive way?

Thanks again Greg!

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The text above is a follow-up to ...

-----Question-----
Hello Greg,

Thank you for taking the time to answer my question.

I just bought a house with a dozen large (7 ft tall) groups of these fencepost cactus plants flanking the driveway.  They were healthy when I moved in 3 months ago.  Since then, they have become yellow and are developing what I can best describe as scabs on their arms. Their arms are also dropping/bending closer to the ground everyday.  And, i think they have also begun to shrivel at the ends.

I live in Los Angeles, California.  They are watered for 5 minutes once a day.  I have other fenceposts in my main yard which receive much more water that are beautiful.

Sound familiar to you?

Thank you!
-----Answer-----
Dear Gretchen

I would water them a lot longer than 5 minutes and then only water once per week. The reason is that watering that often for that little amount of time creates a build up of salts in the soil which will damage or kill the plants. It will take a few deep waterings to leach the salts out of the soil and hopefully if the roots are not too damaged, the plants will recover just fine.

Hope this helps.

Sincerely,

Greg

Answer
Dear Gretchen,

Water for at least 20 to 30 minutes. The let it dry completely beforew watering again. If its on a sprinkler system, once every 2 weeks for 30 minutes would work, but only if there is no rain. You don't want to over water cactus. Good luck!

Sincerely,

Greg