Yesterday, I purchased two Mammillaria, prolifera and nivosa. Both are said to be moisture sensitive, and I can be known as a heavy handed waterer. With both cacti are pretty good looking soils, primarly a good shot of pumice and some potting soil. Which is the same I use with less sensitive plants.
My question is this, should I change to a gritty mix at the expence of disturbing the roots, and possibly the cactus itself. Or should I leave it with its mix, and water heavily as I do? I would be less concerned if this were April, but the presence of a good quality soil throws me off, I get so many plants in regular potting soil.
Changing soils
-
greenknight
- Posts: 4818
- Joined: Tue Apr 30, 2013 4:18 am
- Location: SW Washington State zone 8b
Re: Changing soils
You should water heavily, just not very often. 
Seriously, when you water always give enough that a generous amount comes out of the drain holes. Do not leave the pots sitting in water, dump out the drainage trays. Don't water again until the soil dries out completely. A gritty mix will help, but it's not a cure-all - you still need to restrain yourself from watering too often!
Over the Autumn and Winter they should be kept much drier so they go dormant. Very close to the dormant season now, maybe time for one watering before you dry them out for the Winter. If you can keep them cool, below 50' f, you can withhold water completely until Spring - if they're in a heated room, they may need water once or twice.
If they were in peat, you'd really need to change the soil now, since dried-out peat is resistant to moisture. Since they're in fairly good mix, you could wait until Spring. You could also change the soil going into the dormant season, just not water them afterward. Either way will work.
I don't know where you heard those two species were especially moisture-sensitive. M prolifera is a typical watery-sap Mammillaria, all of which rot easily and require careful watering. M. nivosa has milky sap, those Mamms are a bit less moisture sensitive.
Seriously, when you water always give enough that a generous amount comes out of the drain holes. Do not leave the pots sitting in water, dump out the drainage trays. Don't water again until the soil dries out completely. A gritty mix will help, but it's not a cure-all - you still need to restrain yourself from watering too often! Over the Autumn and Winter they should be kept much drier so they go dormant. Very close to the dormant season now, maybe time for one watering before you dry them out for the Winter. If you can keep them cool, below 50' f, you can withhold water completely until Spring - if they're in a heated room, they may need water once or twice.
If they were in peat, you'd really need to change the soil now, since dried-out peat is resistant to moisture. Since they're in fairly good mix, you could wait until Spring. You could also change the soil going into the dormant season, just not water them afterward. Either way will work.
I don't know where you heard those two species were especially moisture-sensitive. M prolifera is a typical watery-sap Mammillaria, all of which rot easily and require careful watering. M. nivosa has milky sap, those Mamms are a bit less moisture sensitive.
Spence 