Hello Laura,

Thanks for reaching out to the UNH Extension Infoline. Whenever thinking about houseplants, it is helpful to always remember where they came from- where do they grow naturally and under what conditions?

The night-flowering cereus (Epiphyllum oxypetalum) is from the rain forests of Central America and is an epiphyte or lithophyte- meaning that it usually grows not in the ground but on other plants (trees) or on rocks, anchoring itself with its roots to cracks and crevasses.

Many of the problems that these plants tend to have as potted plants grown in non-tropical areas are the result of improper soil and too much water leading to root rot. In their natural environment, they use their root system to cling to trees and rocks instead the ground so water naturally flows away from their root system. As a houseplant, we need to make sure that the planting media has plenty of drainage. Wait until the soil is dried out before watering again and reduce watering altogether during the winter months.

Given the spots on the leaves of your plant, I would re-pot it sooner than later and make sure the potting mix is made for cacti. Using a ceramic pot, if you aren't already, might help to prevent root rot as well.

If you make sure your soil drains well and you aren't overwatering, but you continue to see spots appear, it's possible your plant is suffering from a bacterial or fungal disease. In that case, I would recommend sending a sample to the UNH Plant Diagnostic Lab for analysis. For more information about that see this link-

https://extension.unh.edu/agriculture-gardens/pest-disease-growing-tools/plant-diagnostic-lab

For more information about these plants, have a look at this resource-

https://plants.ces.ncsu.edu/plants/epiphyllum-oxypetalum/

I hope this helps and please get in touch with any further questions!