Some questions about heat

[Shane]

I recently moved and am adjusting to my new space. The new space gets many more hours of sun than the old one did, and also gets hotter (the climate is the same, it's just more sun = more heat). Some of my cacti don't seem to be liking it and I'm trying to figure out what to do. Here's an example of one:

yikes!

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It doesn't quite look like sunburn, but it clearly got too hot. Side question here: is it going to recover, scar and continue growing, or is the top just dead now? Also, did waiting too long to water it contribute? It seemed fine for the first few days

current setup

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My new backyard is quite hot. There's a filled in pool surrounded by a concrete pool deck. I'm trying to reduce the heat without using heavy shade cloth that might not let an adequate amount of light through. I put up some 30% shade cloth, but I'm not sure it's really 30% or blocking a meaningful amount of light. Here's what it looks like

30%???

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And 40% shade for reference

40%

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I think my eventual goal is to put the plants all on tables and set up some more permanent shade cloth. Until then, what's the best course of action? I'm thinking packing the plants as densely as possible to minimize sun hitting the pool deck and moving vulnerable looking plants closer to the south fence (this is a small space though and it can only fit a limited amount of plants). I'm going to put my non cacti succulents under 40% shade in front the cacti in the pool. I'm hoping having a large area of shade cloth will help also. Maybe growing some weeds/grass in the pool would be a good longer term way to reduce heat as well?

[7george]

Just some notes.

• Western exposure is much more dangerous then other combining afternoon heat with sunshine.

• September sunshine is often also more harmful because sun does lower and hits cacti from the side where plants are less protected and trained for that.

• Even 40% shading can be not enough in many cases in hot conditions. Recently I mentioned shading of Joël Lodé and its shade is quite substantial taking into account glass above those sheets.
  https://www.cactuspro.com/forum/read.php?1,587785

• The wall of plants in your yard may restrict air movement and thus contributing to sunburn probability.

Moving cacti during the active season is always stressful. I'd put some pots into a real shade for some time if no other option is in site.

[keith]

I use 50% shade cloth for most cactus but if slowly acclimated to full sun many cactus do fine just make sure the pot sides don't get too hot in full sun. Sunburn usually scars but wont kill the plant unless its just just left out to bake.

[MikeInOz]

I put some of my sun loving cacti outside in full sun in the summer. Anything up to about 30C (86F) seems to be trouble free but over that I have to keep a carful eye on them. If it's not too hot (about 35 or so (95F), I break off some twigs and branches of a fine leaved tree from the garden and place them on some of the plants with fewer protective spines and they get by ok. The white Mamms etc are still ok without protection. If it gets to 38-40C (over 100F) I put heavy white shade cloth over the whole lot. Sometimes - mainly Ferocactus - are the first to show the wrinkling and pale epidermis but if I catch it quickly they recover overnight. Your plant Shane, is showing some permanent damage towards the center. Unless they are rare plants that throw side shoots I would throw such a plant away. Life's too short to persist with them.
Also, they seem to enjoy a cool light misting after the sun has gone down after a stinking hot day.

[Shane]

Thanks for the responses. I feel like I have the situation under better control now (or at least I'm not panicking anymore haha). I redid the shade cloth setup and I feel better about it now. At my old place there was a more shade and I didn't fully appreciate how much until after my plants burned. The damage was luckily minimal for the most part. The plant in the picture has mostly healed and only has a little scarring. @MikeInOz It's not a rare plant, but I don't plan to throw it away. If I tossed all my non rare plants that didn't look perfect I wouldn't have many plants left...

My yard is actually really nice in terms of the light it offers. The back fence (covered in vines in the picture) blocks the western light and the fence to the left blocks light from the south to some degree, providing some good options for giving plants less light. On top of that, the fences are great for hanging shade cloth. Hanging the shade cloth from the fences also solves the problem of the September sun sneaking in to the South or West

I'm actually on the verge of taking the shade cloth down. I'm probably going to pull the "30"% shade off the cacti this week (they're adjusted to the light now and also it's gotten cooler) and am strongly considering taking the shade (~50%) off the succulents if it continues to be in the 70s. I'd rather use as little shade as possible

Side note about the morning glories in the back. I've removed them between the ground and about knee height along most of the fence because I'm worried they'll become a reservoir bugs potentially (they're still rooted into the ground on the other side of the fence so cutting them hasn't killed them)