T. valdezianus -- this is ridiculous...

[Steve Johnson]

...But in a good way! Can't say the same with effort #1, when I got my first Turbinicarpus valdezianus from the California Cactus Center at the beginning of March 2012. When I changed out the CCC's nursery mix in favor of pumice/DG mix, my failure to thoroughly clean the roots first resulted in excessive corking. Effort #2 came bare-root from CoronaCactus in July of that year, and the results have been much better. Here's a before-and-after showing the Turb's progress from mid-May 2013 to today:



You'll notice a couple of things at work here -- first, the effect of 2 solid growing seasons in coarse pumice/DG aggregate. And second, growth in the taproot has been pushing the base up above the top dressing. Just to give you a sense of perspective, the valdezianus has been growing in a 2.5" x 2.25" terracotta pot:



The valdezianus obviously needs a deeper pot. A problem we have with mass-produced terracotta is the fact that pot sizes are fairly standardized, so add this to a taproot which loves to grow in mineral mix, and the plant is about ready for a handmade glazed ceramic pot that'll be deep enough, but not too wide. I found the perfect pot for it recently, so repotting time will be in about 3 months. Finding handmade pots in the sizes I need hasn't been easy, but I'll be on the hunt with some local sources I know. So that's my big project for the winter -- hopefully 40-some-odd cacti living in terracotta will move to glazed ceramic before spring comes around again. In the meantime...

The valdezianus with a brand-new bud starting to show:



I think there may be another bud as well, although too early to tell yet. In the past I haven't seen valdezianus in flower prior to February, and its buds do take a long time to develop. However, this one is well ahead of schedule compared with the last 2 years. Perhaps valdezianus flowers in January? That'd be nice!

[Ivan C]

"When I changed out the CCC's nursery mix in favor of pumice/DG mix, my failure to thoroughly clean the roots first resulted in excessive corking."

Steve, why do you suspect that the lack of thorough root cleaning caused the corking? I thoroughly cleaned all my plant's roots last year and repotted in a much courser mix and I got a number of plants with excessive corking for a few months. Near the end of the summer all the new growth was back as green and healthy as it should be. I have not been able to figure out why this happened. And not to all the plants either.

[DaveW]

Corking is simply a normal sign of ageing of the epidermis, just like the bark of a tree and is natural as a plant ages. The harder a plant is grown usually the sooner it corks at the base and it usually persists on taller growing cacti. However it can often disappear down to ground level on smaller growing cacti when more vigorous new growth occurs. I would have thought if fairly neutral in PH the only difference the soil would make is to how hard the plant is grown, but also that could depend on how dry the soil is kept so the plant grows more slowly. You often see it on old window grown cacti where the owner has heard cacti only need a teaspoon of water a month, therefore they have grown very slow and hard.

I have seen it claimed a couple of times that an acid compost and iron feed help to delay the onset of basal corking in some S. American cacti, but how true that is I don't know, or if it would apply to the more alkaline tolerant N. American cacti.

See corking down this link:-

http://cactiguide.com/cactipests/" onclick="window.open(this.href);return false;

[Steve Johnson]

Steve, why do you suspect that the lack of thorough root cleaning caused the corking? I thoroughly cleaned all my plant's roots last year and repotted in a much courser mix and I got a number of plants with excessive corking for a few months. Near the end of the summer all the new growth was back as green and healthy as it should be. I have not been able to figure out why this happened. And not to all the plants either.

A fair question, and it's possible that the excessive corking on my first valdezianus would've happened regardless of what I did. I brought it home from the CCC on March 3, 2012 -- here's the plant when I repotted it the next day, followed by what it looked like 2 months later:



There's a more plausible possibility, and I should've included it when I began this thread. If the valdezianus wasn't 100% happy with how it was being grown before I got it, fairly rapid corking would be the response as the plant was concentrating its nutrient energy on producing healthier new growth. While this theory isn't original thinking on my part, I believe Ian put my mind on an interesting track here. Although the link references my Turb klinkerianus, I believe the basic phenomenon we're discussing also applies to the Pelecyphora strobiliformis that came from TimN's collection in AZ last year. The commonality here -- old, slow-growing cacti that seem to prefer my cultivation practices over what the previous grower(s) did. I know that my first valdezianus was already on the older side when I got it, so it certainly fits the profile. If I had more growing space, I wouldn't have minded keeping both. Unfortunately I don't, and since the species isn't all that difficult to find, I was quite happy to give my ugly old valdezianus a good home with Gary Duke of the Long Beach Cactus Club. Darryl did a great job of growing the valdezianus I currently have, so I'm pleased that the transition from his collection to mine made up for the disappointment I experienced with the results coming out of effort #1.

[Steve Johnson]

Corking is simply a normal sign of ageing of the epidermis, just like the bark of a tree and is natural as a plant ages. The harder a plant is grown usually the sooner it corks at the base...

What you're saying is certainly true, and I can tell you for a fact that the cacti being sold by the CCC come potted in a rich medium I wouldn't even think about using. Since I prefer growing my cacti hard (at least to a certain extent), it's one of the reasons why I stopped buying plants there quite some time ago.