Cactus and Succulents forum: Repotting- what to put at the bottom

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MazerRakham
Apr 30, 2018 8:46 PM CST
I am looking repot several of my cacti. My question is, what and how should I arrange the bottom? Up until this point, I've been putting a few layers of newspaper at the bottom; the local greenhouse suggested coffee strainers; I've read from some other places that are recommending mesh screens at the bottom with some mixture of larger rock on top of that.

For reference, my soil mixture is 70% cactus potting soil, 30% pummice.

When I water the cacti, I usually give them enough water until it runs out the bottom. Then I let the water sit, allowing the cacti to slowly drink it up from the dish. If I use a system where I put rocks at the very bottom, it would appear to me that they would prevent the cacti from sucking the water? Would that be a bad thing?

Another reason I ask is for the purposes of future repotting. If I use a hard clay pot, it would make sense that a layer of rock at the bottom would make pushing the cactus out easier.

Let me know what you think.
Name: Daisy I
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DaisyI
Apr 30, 2018 9:07 PM CST
Welcome!

First, why do you feel you need to repot? Repotting is highly over-rated. Its right at the top of the list with fertilizing (I rarely do either Smiling ). Cactus are native to some of the poorest soil on earth.

When I do repot, I put a single layer of newspaper in the bottom of the pot. About the time it rots away, the soil has decided not to run out the bottom. And, there is nothing in the way of the water flow.

You are playing a dangerous game by allowing the pot to sit in a saucer of water. Cactus roots are strange in the plant world - they absorb moisture until there is no more moisture to absorb, often over-doing it in the process. Cactus need to have the water run past their roots and then they need a dry time.

Don't put a layer of rocks or pot shards or styrofoam or wine corks or ... at the bottom of any pot. It acts as an artificial shelf that holds water. The result is the soil will be saturdated before the water runs out the drain hole and your cactus will be a pile of muck. Sad
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MazerRakham
May 1, 2018 2:00 AM CST
DaisyI said: Welcome!

First, why do you feel you need to repot? Repotting is highly over-rated. Its right at the top of the list with fertilizing (I rarely do either Smiling ). Cactus are native to some of the poorest soil on earth.


I have read a number of articles that have stated that they should be repotted once every 2-3 years due to diminished nutrients in the soil as well as calcium and salt buildup due to tap water which over time inhibit the cacti's absorption ability through its roots. Is this incorrect?

DaisyI said:
You are playing a dangerous game by allowing the pot to sit in a saucer of water. Cactus roots are strange in the plant world - they absorb moisture until there is no more moisture to absorb, often over-doing it in the process. Cactus need to have the water run past their roots and then they need a dry time.


Should I be draining the excess water?

Name: Baja
Baja California (Zone 11b)
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Baja_Costero
May 1, 2018 9:29 AM CST

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Daisy has given you some excellent advice. My perspective here...

I don't repot most of my cacti except when they need more space. I do provide regular weak nutrients when I water, so I'm not relying on years-old cactus soil to provide that for my plants. If you do unpot them and replace the soil, do it very gently and be sure not to water for at least a week afterwards. Every time you do this there is a risk of rot if damaged roots get submerged too soon.

The only thing other than soil components that I usually leave at the bottom of a pot is a small square of window screen just big enough to cover the hole. The rocks at the bottom do not typically work to your advantage. With some pots that have lots of holes I might put a single sheet of paper towel cut to size, and the paper towel will disintegrate over time.

The issue of salt buildup in the soil can be avoided by flushing every time you water. If you make sure that some water exits the container every time you water (say 1/4 of the total) and does not get slurped back up, you're providing an exit for salt so it does not build up.

I prefer to water in more than one pass (separated by a few minutes), rather than leaving pots in saucers full of water. But the goal is the same: to water to completion. You could wait until they have slurped up what's in the dish and then water one more time, emptying out the final pass through at the end. More on the process here.

The thread "Sunday afternoon experiment: watering in multiple passes" in Gardening Ideas forum

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