If your soil is rich, or you added a substantial amount or compost when you initially planted the dragonfruit cactus plants, you likely will not need to fertilize again for several months (2-3 months before the first fertilization). However, after the first few months at the latest as the dragonfruit cactus plants start growing, you will most likely need to start fertilizing regularly.
Dragonfruit Fertilization Guidelines: The following are guidelines for dragonfruit Fertilization. Depending upon your soil conditions, your location, your climate, and a myriad of other parameters you will need to modify these general guidelines to suit your dragonfruit growing needs! The individual dragon fruit growing conditions of your location will be the final judge of how much and how often you fertilize. Do not over fertilize, if your location does not require it.
Dragonfruit Fertilization First Year: Fertilization of the dragonfruit cactus during the first year after planting should done more frequently than later as the dragonfruit cactus matures. For the first year after planting, fertilize every 8 weeks or so with with light doses of about 1/4 lb for each dragonfruit cactus plant with a fertilizer of 6-6-6 or 8-4-12 (or so called palm fertilizers for tropical plants) with a few % of magnesium. Use of other fertilizer mixtures of similar content is acceptable of course.
Dragonfruit Fertilization Second and Third Years: During the second and third years after planting the dragonfruit cactus plant, gradually increase dry fertilizer to about 1/3 lb per dragonfruit cactus every two months. Use manure or compost of about 6 lbs per cactus every 6 months.
Dragonfruit Fertilization Ongoing Years: In years after, you may want to increase fertilizer to 1/2 to 3/4 lbs of fertilizer per cactus plan, using 3 to 4 applications per year. Apply manure or compost using about 5 lbs for each dragon fruit plant approximately semi-annually.