One of the arms of my in ground cactus is getting tall (10 feet) and is hitting the wall of our house. Can I cut it in half and plant the limb for a new cactus? If so, what is the best way to do it?
These articles should help: https://www.gardeningknowhow.com/ornamental/cacti-succulents/organ-pipe-cactus/organ-pipe-cactus-care.htm
What are the steps for trimming an Organ Pipe cactus?
This cactus is very slow growing, but can reach a 10 foot diameter in 150 years. If it has been planted too close to it's neighbor, someone didn't take later growth into consideration.
To trim an arm, (branch) on this cactus, you should use a very sharp saw and cut as close to the base of the plant as possible.
If you are asking about trimming the entire plant, this is what I would suggest. If the plant is too tall, and there is a subspecies that grows to only 10' tall, take out the tallest arms. DO NOT saw off the arms to shorten the plant. The plant will initiate new growth at the injury site. The new growth will be too heavy and weigh the arm down, causing more injury, or an unsightly appearance.
What are the fluffs of cotton where the thorns should be?
This is likely Scale pests.
They can be scraped away from the plant.
Neem Oil can also be used to treat Scale.
Here are some links with more information.
my organ pipe catus is in a pot out side and is starting to turn brownish purple on the top section. what can be wrong. It has been out side for about two years with no problem.
The Organ Pipe Cactus does turn grey as it matures and ages.
This article has more information.
One of my pipes broke off mid cactus; can I plant the broken piece and if so, does the end have to dry out first?
Yes, you can propagate your Cactus piece.
This article will help you with this task.
I have a mature old organ pipe cactus and in this last year many of the limbs are starting to fall over. Was wondering what can I do in this case? Is it normal for them to do this? Or do I have a problem such as over or under watering? thanks!
This actually sounds like a case of over-watering. These are very drought tolerant, and will not tolerate "wet feet" for very long. I would let the potting material dry out pretty well in between waterings. You might apply a few drops of rosemary oil in the water for the next watering, just in case an infection is trying to start in.
Here is an article for more information on this cactus: https://www.gardeningknowhow.com/ornamental/cacti-succulents/organ-pipe-cactus/organ-pipe-cactus-care.htm
My organ pipe cactus has a problem on one arm See photo. Where is wrong and how do I fix it? Thank you.
It looks like it has sustained damage at one time. If this spot doesn't spread, then it will not harm the cactus. If it is spreading, then it could be an infection. If this is the case, then I would recommend applying peroxide to the wound. Also use some wettable sulfur around the base according to the instructions on the package.