K writes:

I have a large cactus, a Mammillaria. It's about 2 ft long and 4
inches diameter, and, typically of its type, it has keeled over and is
sprawling across the greenhouse bench.

I've got one that has reached 18" or so and tilts towards the light
when it's been watered. I've got it staked and turn it round when it
starts to tip. Needs to be in a fairly heavy pot to stop it
overbalancing.

Mine flowers regularly and I've grown a lot of little ones from the
seed pods that appear a year or two after the flowers.

Anthony