Hi, I just joined this web site. What a resource!! Every spring I never know when to re-pot cacti ( every 2 years or so?), and when to and how long to firtilize? some are 15 years old and some are already blooming.... I live in Vancouver and it's soooooo cold these days... I am putting off all spring work with indoor plants. Cactus gal
Welcome to the site:} I have the luxury of not having to wait for the right season to pot as they grow through most of the year here. I generally pot up my plants when I've noticed the growth slow right down. (not seasonal dormancy, plants tend to slow somewhat once they've reached their limit in a pot) Because different plants grow at different speeds it's too hard to say re-pot every 12 months or so. While watering pots a good amount of nutrient is washed out so fertilising the pot is pretty important, but because they are watered less often it's not as neccesary to do as often. I fert once in spring and again after summer with an organic fert. I'd say a spring fert would be enough in colder climates with an occasional foliar feed of soluble fertiliser like fish emulsion or I have a combination seaweed/fish emulsion/worm casting which does well. Hopefully someone with more cooler temp experience will be able to add some more relevant info for you.
As Chungii V wrote, the repotting intervals varies a lot between different species and growing conditions. I repot the most fast-growing species twice a year, the "normal" cacti in 1-2 year intervals. The really slow ones are repotted less frequently, approximately after 3-4 years. I mix some slow-release fertilizer in my soil mix, and add soluble fertilizer (1/4 - 1/2 normal dose) to the water from late May to early August. Remember to use fertilizers low in nitrogen.
