DF is very forgiving when it comes to soil. But put together a good, well draining mix. Really, any good potting soil from the store will do. You didn't include the zone you are in. Can the plant be kept outdoors? If so, I would plant it in the ground versus the container. If not, find a decent sized tub, nothing crazy big. You'll need to figure out a way to support the plant as it grows and starts to branch out. There is tons of pictures and info out on the web about DF support. You should get plenty of ideas there. If the plant is outside when blooming, you may get enough insects to pollinate. I would still help them along and hand pollinate each bloom. They will open up after it gets dark. Once open, get a brush about the size of your thumb and start knocking off the pollen into your hand. Go around to the other flowers and deposit a bunch of pollen into the stigma of the flower. Just keep repeating that with each flower. come morning, the blooms will start to die off. Hopefully in a few days, you will see a small DF starting to form.

Hey there, I bought two dragon fruit cuttings already rooted in 1 gal pots back in April and put them in a single 15 gal pot inside a trellis on wheels. The trellis is 6ft high and 18" wide. I pruned my dragon fruit heavily until the main stems reached the top. The vines want to send out lots of lateral growth, but I've seen commercial growers prune them to a single vine. Then, once they reach past the top, cut the stems, sending out lots of outward growth. I still get some shoots coming off the main stem but I always pinch them off.

Red flesh ones are usually sweeter than most white flesh ones So you'll like them a lot better. If you only ever had store bought bland white flesh ones and didn't like them. Well, your mind will change, when you guys get to try a home grown ripe fruit. Let them be as of now, let the plant finishing fruiting and ripening them. Then you can hack away the plant of any limbs, you don't want. Those smaller thinner weaker limbs, are actually new growth, that hasn't quite mature and thus is why they are weak looking. If you can bundle or tie them to the trellis and make them climb up and over the trellis, they will naturally and eventually stick on to the wood post with their aerial roots. You can cut some of those none fruiting thick branches off. Cut close to the main stem/branch, that is going up the wood post. The new growth will be easier to train to climb up the wood post/trellis later. As for cutting the branches, you can cut above or below the joint. They will root either way, but before you attempt to root, let the branches/cuttings heal/dry and the wounds have closed for 3-5 days. This will prevent the newly wounded exposed part from rotting, once you can put them in the ground. And if you do offer them up for trading/buying/postage charges, you should wait until people actually want them, so then you can make fresh cut and the cuttings will be fresher won't be drying up too much.

Geographically, my plant is in coastal Los Angeles, less than three miles from the ocean. Climate here varies greatly as you get further from the beach, and I am close enough to get the coastal influence that keeps the summers from getting too hot and also keeps the winters from ever having frost. It's not tropical - it's very similar to the climate in South Africa. I'm not that familiar with the climate in London - but from what I've heard, it is also very mild. However, I do know that I get a lot more sun in the winter than London does, even though winter is our rainy season. It does not get below 40°F where I live, mean temperature in January is 58°F. I would think that anyone growing a dragon fruit plant would want to get fruit from it, as it is quite delicious. That's the only reason I am growing it. You can only see the flowers at night and early the next morning, and so that's not much of a reason. And yes, my plant stays outdoors all year - it is extremely difficult to move once it gets to a certain size, and as I said before, the arms get brittle and break easily when they are very long.