Geometricus issue

[Jura]

Hey guys,

So this one was overwintered as dry as possible and it has very draining soil. However cladode looks quite black in tint when comparing to the healthier one. I'm just wondering if this is not?

Also I've taken it out of the pot to check the root system, and it didn't expand since I've got it, it's quite small lump of roots... Just wondering, what am I doing wrong and if this black cladode should be cut off?

[greenknight]

I don't see any problem with it. The darker cladode is more like they typically look in habitat. How long have you had it?

[Jura]

Hey there,

I have it since September last year.

The thing that worries me a lot though is the root system, since I've got geometricus it never really developed further. Its in very draining soil and it got 1 watering with fertiliser.

I have another cladode and roots grew so big that it became pot bound its not like they are getting different care, its odd..

[greenknight]

You described it as a small lump of roots - is it in a gob of dried-out peat, as described in this thread? : http://www.cactiguide.com/forum/viewtop ... =25&t=9222

[Jura]

Hey there,

There doesn't seem to be any peat.

This is how it looked when I got it and quite frankly it haven't changed at all

[greenknight]

Looks like they lost most of the roots when they dug it up, or it was a barely-rooted cutting.

It's going to have to grow more roots before it can make much top growth. You got it near the end of the growing season last year, and this season is just beginning in northern climates - it hasn't had time to do much of anything since you got it. It's a slow-growing species to begin with, and this loss of roots is a setback for it. You're going to need patience. Fertilizer isn't going to help much until it has some roots to take it up with.

It's best to pot cacti in a pot only a little larger than the root ball - obviously, that's not going to work with this. What I would do with one in this condition is put some largish stones in the bottom of the pot to take up the extra space, working some potting mix down between the rocks to make drainage channels, then plant the cactus in the reduced space above that. That way, you don't have a lot of mix staying wet in the bottom of the pot where the roots don't reach.

Without doing that, you'll need to water very cautiously, like it's a newly-rooted cutting. Just give shallow waterings for a while, gradually water deeper as it shows signs of rooting down.

[Jura]

Hey there,

Thank you for this reply. Extremely helpful!

I have pretty large red lava rocks, about 1-2cm in diameter. At the moment geometricus is in sand+molar clay+small lava rock mix, so if I just mix in larger stones, let's say 50/50 with current soil would it work?

[greenknight]

It wouldn't have the same effect. The point of putting the rocks in the bottom of the pot is to reduce the amount of mix in the saturation zone - there's a phenomenon called a perched water table, a level below which the water doesn't drain, its depth depending on the size of the pore spaces in the mix. It's explained here: https://gardening.stackexchange.com/que ... ater-table

Adding rocks to the mix would reduce the amount of water it would hold, so the amount held in the perched water table would be less - but it's more effective if the rocks are all in the bottom, displacing mix that would remain saturated.

More effective than adding rocks to the mix would be to pot it in straight gravel, the pore spaces would be so large the perched water table is eliminated. Many people grow cacti this way with great success, and it does encourage strong root growth. You have to water more often, with a weak fertilizer solution at every watering since the medium doesn't retain nutrients. If you don't mind the extra trouble, this would work well.

Another method some use to eliminate the perched water table is to have a wick coming out of the drain hole hanging down below the pot. The perched water table moves down into the wick, the potting mix no longer remains saturated.

I've had good success with the rocks in the bottom method, but any of these techniques will work to eliminate the danger of the mix going sour in the bottom of the pot - and that's the main danger you face with this cactus having such a small root system.

[Jura]

Hey there,

I thought ill give you an update.

So I did exactly as you said, and I can see improvement already!

2 weeks on, I gently checked its roots and I could see new roots forming which is fantastic outcome given that it was so stubborn all along. Thank you so much for your advise, it really worked and you possibly saved my tephrocactus

[greenknight]

That's great to hear.

[Jura]

Hey there,

Thought ill share progress again, I finally see new growth and compared 2 photos of before repot and after, its an amazing difference in nearly 2 months. It seems happier than ever

[greenknight]

Looking really good