Orange spots on Gymnocalycium ragonesii

[Cacidy]

Just noticed some orange spots on my G. ragonesii. 2 days before this showed up I took a plastic sheeting that was covering my plant rack off, leaving just a window screen that was underneath it before. I did this because I thought my cactus needed more light. Most of the other cacti look ok but this guy got orange spots. Could it be sunburn? I have a friend who keeps one in morning shade direct afternoon light and I noticed the same spots, we got them from the same grower. I use 5.5 pH fertilized water with ammonium sulfate a la Elton Roberts. Also what do you guys think the green area on the plant right above the soil line is?

Thanks for any advice!

[Steve Johnson]

Just noticed some orange spots on my G. ragonesii. 2 days before this showed up I took a plastic sheeting that was covering my plant rack off, leaving just a window screen that was underneath it before. I did this because I thought my cactus needed more light. Most of the other cacti look ok but this guy got orange spots. Could it be sunburn? I have a friend who keeps one in morning shade direct afternoon light and I noticed the same spots, we got them from the same grower. I use 5.5 pH fertilized water with ammonium sulfate a la Elton Roberts.

I'd say definitely sunburn. Morning and late afternoon sun is fine, but full sun in the middle of the day can be a problem for cacti prone to sunburn/scorching. A free flow of air around the plant certainly helps, although you may want to give your vulnerable cacti some mid-day shade protection when daytime highs go above 90F. Your fert regimen sounds good, although I tried Elton's Ammonium sulfate supplementation idea and it didn't seem to make much difference. The quality of your water is a different concern -- if you can water your cacti with stored rainwater, that's the best. However, if you have to use hard tap water, acidification is really helpful (Elton is spot-on about that one!). If you're not already making this part of your growing practice, I can give you a few pointers.

Also what do you guys think the green area on the plant right above the soil line is?

I've seen this in Gymnos before, and I think it's caused by using soil-heavy mixes. If I'm correct about that, you may want to lean out your mix more with a good additional dose of pumice or granite gravel. I went soil-less in 2012, and that's the way I grow the vast majority of my cacti. The results have been excellent, so unless you live in a really dry climate, this is a possibility worth considering.

While we're here -- it's highly recommended that forum members include basic location and climate info in their profiles. Then whenever they ask for advice, respondents are more likely to produce useful answers. See the following screenshots:



Here's my profile as an example:



If you live in the US, you can reference the USDA Plant Hardiness Zone Map for your profile:

http://planthardiness.ars.usda.gov/PHZMWeb/

Hope this helps!

[Cacidy]

Thank you that was tremendous help. I updated my profile info. I am in Sacramento (9b) and we have had many days above 90 this summer. I currently keep my plants in wire racks wrapped in window screen. I have a 14inch box fan (non-oscillating) blowing across them. I am going to build a greenhouse soon. I'll give these guys some more shade.

I do acdify my water to what I THINK is close to 5.5 pH. I only have the liquid indicator, so I go for 'peachy orange'. Another nurseryman told me he tried the ammonium sulfate as well and ended up switching to calcium nitrate with better results. I have yet to try it. Honestly I would like a recommendation on what kind of balanced water soluble ferts you use, as I can only find the pellets of ammonium sulfate and I hate crushing them.

Thank you for the info regarding the soil mix. I have not transplanted this guy into my soil mix yet, and the nurseries soil is indeed rich and has peat in it. I will give it a leaner mix. I use 70% pumice/20% DG/10% compost.

Do you mind if I ask what you use/ratios for your soil-less mixture?

Thanks a bunch!

[Steve Johnson]

Thank you that was tremendous help. I updated my profile info. I am in Sacramento (9b) and we have had many days above 90 this summer. I currently keep my plants in wire racks wrapped in window screen. I have a 14inch box fan (non-oscillating) blowing across them. I am going to build a greenhouse soon. I'll give these guys some more shade.

I do acdify my water to what I THINK is close to 5.5 pH. I only have the liquid indicator, so I go for 'peachy orange'. Another nurseryman told me he tried the ammonium sulfate as well and ended up switching to calcium nitrate with better results. I have yet to try it. Honestly I would like a recommendation on what kind of balanced water soluble ferts you use, as I can only find the pellets of ammonium sulfate and I hate crushing them.

Thank you for the info regarding the soil mix. I have not transplanted this guy into my soil mix yet, and the nurseries soil is indeed rich and has peat in it. I will give it a leaner mix. I use 70% pumice/20% DG/10% compost.

Do you mind if I ask what you use/ratios for your soil-less mixture?

Thanks a bunch!

You're most welcome! The only fert I use is Dyna Gro All-Pro 7-7-7 liquid concentrate diluted at 1/2 teaspoon per gallon of water. The NPK balance is perfect for cacti, and Dyna-Gro's nutrient profile includes minor and micronutrients. IMO excellent, and the Dyno Gro people really know their stuff. By the way -- if you decide to go soil-less, you'll need to fertilize pretty much every time you water. Nice thing about acidified water is that fertilizer salts generally don't build up in the pot unless you overdo it. With that said, it's not a bad idea to flush your pots once a year in the spring or summer. A good deep drench with rainwater and nothing more will do the trick too.

If you want to go crazy nutso on testing the pH of your water, you can find a presentation I posted here:

viewtopic.php?f=31&t=34730&p=323572#p323572

The pumice-to-granite ratio in my soil-less mix is roughly 3-2, and it looks like this:



Always be sure to thoroughly rinse mineral gravels in running water before you use them in a mix.