Is my Mammillaria rotting? #651390 - Ask Extension

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Is my Mammillaria rotting? #651390

Asked June 15, 2020, 4:53 PM EDT

When I was getting ready to water her she was very loose and it turns out her roots are falling off, there are some roots left on her so I put her in new moist soil. I don't honestly know how much water I should be giving her and how long until I water her again so I won't overwater her which is what I'm guessing, I water her every 10 days.

St. Clair County Michigan

Expert Response

Ok  My first question is... are you using potting soil that is specifically for cactuses?
Regular potting soil will hold too much water.  Cactus grows on very sandy, fast draining soil
You want to imitate the natural growing cycle.  In the spring when the arid parts of the country get rain, is when cactus grow.  The rest of the year, they live off the water stored in their "bodies" with an occasional shower.
When the top 3" of soil in your pot is dry, is the time to water... not once a week.
You could invest in a soil moisture meter so you can be certain.
Water the plant thoroughly so that water runs out the bottom and then don't water again until "bone dry" to quote some sources.
The potting medium should never be more moist than a wrung out sponge.
According to the article I read... that means every couple of weeks in the summer , dropping to every 4-6 weeks in the winter.  
You have some root there, so I would put the little guy back in a pot with the soil just damp and then leave it alone until the top 3 " are dry.
Mary Kretschman Replied June 16, 2020, 1:10 PM EDT
Yes I'm using a soil for succulent and cactus. I just ordered a soil meter and it's on it's way, thank you for you advice.
The Question Asker Replied June 18, 2020, 6:32 AM EDT
You are welcome
Mary Kretschman Replied June 18, 2020, 8:12 AM EDT

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