hello! i have a leaning tower of cactus and it needs help! i don't know what kind of cactus it is but i got it from a friend from somewhere in south america. i planted it in the ground in florida. it's been growing for about a year now and as you can see, it is listing badly. seems to also have some black areas and white areas on it. i'd like to know what i should do to help this guy get heathy again. any ideas or suggestions would be welcomed and greatly appreciated!!
You might cut the tall one down and leave the small shoot. The small one looks healthy but the old one looks like it has some problems down at the base. He's right about the humidity and water but I doubt that would be it given that cactus is probably several years old and most likely used to these conditions. Perhaps someone in the cactus forum could give more insight.
Also, and this is just an idea as I am in no way an expert, you might try putting some type of impermeable material down around the cactus to prevent water from going to the roots. This way you would create and artificially dry condition for the cactus to grow in.
I would cut off the ugly offending parts (it will sprout some new shoots). You can also root the cut off parts if you want to (do you need a living hedge?) You might raise the cactus above grade in case the soil remains wet.
I have two columnar cacti that I keep in pots (bring those in for winter) that I have cut a few times over the years because once they get to 7 feet tall they are a little dangerous to carry about and are top heavy to boot.
Wished I had a picture of them before I cut them last summer. The only thing I can find is after I cut them plus the cut portions. The cut portions laid on the stone slabs for weeks and I finally rooted them in a shallow trench but let those out for winter. Only the contorted ones made it through winter while the straight ribbed ones all croaked. The last two pictures show the growth they put on since last year.
Here is the results of one of them a few weeks ago.