A few pointers:
1. If youre going to keep the plant indoors forever, you need to think about upsizing the pot soon. To be reasonably successful, dragon fruit needs to have long drooping branches, to allow the plants natural chemistry build up in the downward hanging stalks. Youre probably going to need a solid platform to place the pot on, because to grow tall enough to have hanging branches you need to either have a post for the main stem(s) to grow up, or have the pot high enough in the air to allow branches to grow long enough straight out of the pot. If you have a dedicated window you can grow your plant in front of, the best answer might be to hang it, off SOLID chain from a ceiling rafter or other support. You'll probably have to keep it trimmed down once its mature, as these plants can weigh in the hundreds of pounds if left unmanicured. after that, you can use curtains of various transparency to moderate sunlight to your plants preference.
2. The damage looks fungal to me. Get a sharp, thin knife and sterilize it with rubbing alcohol and cut/scrape the dead sections off or out. You can either sacrifice the stem above the diseased sections or just cut away the bad, down to the central core of the branch. But dont cut the woody core. Think of that like the wood of a tree, and the green section as the bark. You can lose entire branches of the green plant material, but as long as the central core is unharmed, any plant material further down the line will continue growing. As for treating the fungus, I'd try an anti-fungal copper soap spray mix. Its worked pretty well for me in the past to keep my plants reasonably healthy during outbreaks.
3. Just out of curiosity, do you happen to know what type of dragonfruit you got the seeds from? I'd hate to see you go through all this trouble and years of waiting to find out you have a variety thats not self fertile and you'd have to either have to hunt down pollen from other people or have to grow a second plant from seeds/cuttings and have to wait all that time again.
Hi JirkaH. The thin growth is due to lack of sunlight. You mentioned flowers, but your plant is far too young to produce flowers. I’m not sure what the weather/season is like in the Netherlands, but sunlight is a dragonfruits best friend. Without enough sunlight, plant growth will be lacking and flowers won’t ever develop. Did you grow your plant from seed?
Skin issues are a standard problem with dragonfruit. They all get it occasionally, but lack of sunlight doesn’t help with those problems unfortunately.
Sunlight and heat are the best things for healthy dragonfruit growth
Hi, thank you so much for your reply.
I grew this from seeds. Is this a reason why there are no flowers yet, or is it because its still young (approx 1year).
I noticed the dry part started appearing when the plant was exposed to too much sunlight. Which is why I remove it from direct sun for some time.
After your comment I put it back immediately.
How often do you recommend to water it? Its an indoor plant.
Do you also have any other recommendations regarding taking care (fertilizing, vitamins, antipests,...)
Thanks a lot.