My Hoya bella was recently moved outside. It flowered nicely, but now the leaves are a light yellow/green and the soil surface in the pot is covered with moss. What is wrong and what can I do?
Here is some information I found in the book, Subtropical plants: a practical gardening guide (by Jacqueline Sparrow and Gil Hanly, 2002, p. 107), quoted below:
Hoyas do very well in pots. They need bright light, but not sun…Hoyas strike fairly easily from cuttings, taken at the warmest time of the year.
About the yellowing of the leaves…I am pretty confident that this is due to the plant getting too much water (rain, whatever source, while it was outdoors) and the soil not drying out, which also explains what happened to the top of the soil–the moss or algae growth there. I would just gently scrape off the soil surface and put a thin layer of potting soil over it. If the plant starts getting what it needs again (as it did before it was put outdoors), it will hopefully return to its former healthy self.
During its growing season, Hoya bella prefers temps between 64 and 68 degrees; during its rest season, 59 degrees is the recommended minimum temperature (so here in Seattle, right next to a window may be too cold).
University of Florida provides additional information about Hoya bella.