I received a rather tatered looking night blooming jasmine as a gift from a freind who is leaving the coutry. His advice was to water frequently. My questions are how frequently is "frequently" and how do I keep the palnt alive in a bronx apartment? It seems to have what looks like white dust--mold? -- on some of the leaves.
To start, let me give you a little general information about night blooming jasmine. Even though the plant looks and blooms like a jasmine, the funny thing is that it is actually not a jasmine. The proper botanical name is Cestrum nocturnum. I usually find that if you are doing searches on the internet, either to find care information or to find images to confirm that the plant is what we think it is, it helps to search by the formal botanical name to find more credible sources and help forums.
Ok, so, on to your plant. As I mentioned, jasmines and night-blooming jasmines are different plants, but their wants and behaviors are quite similar. And your friends watering suggestions are mostly correct, but I should clarify. Your plant does like frequent watering, but only during it’s active growing season, which is typically summertime. That means that during the winter months when there is less sunlight throughout the day, the plant slows down and its “metabolism”, for lack of a better word, is not nearly as active as during the summer months. For this reason, in winter you want to water your night-blooming jasmine much less often. If the plant is getting a lot of water and unable to take it into it's roots as quickly as in summer, then that water sits in the soil and begins to cause disease issues. The main issue, as it sounds like you have already discovered, that can result from this is an unsightly fungus called powdery mildew. It is not going to kill the plant necessarily, but it is ugly and the plant will be happier without it around.
Moving forward, keep the plant watered, but don’t be afraid to let the soil dry between waterings during the winter and early spring. What I mean by that is water maybe a little bit twice a week. You don’t want the plant to completely dry out and die, but you also don’t want it to be soaked. Right now it needs enough water to stay alive, but not much more than that. It likes sun so close to a window with bright light or some direct sun should be fine. If you have a heater nearby, take that into account as it may be making the plant dry out faster than usual. As the weather gets nicer and the days get longer, feel free to gradually give it more water. You should see that it will be growing more and putting out new leaves and stems and by the summer you can be giving it a couple of glasses of water a week. As for the powdery mildew, you can take a wet paper towel with a little bit of soapy water and clean the white film off the leaves. As soon as it’s nice enough to open the window and get some fresh air in, that is going to be a major help too. Most plants really don’t like to be stuck in these closed up apartments all winter so I think you will find that fresh air will also help the plant out a lot.
Well, now that I have loaded you up with information, I hope that helps. Keep it in a sunny spot and if fresh air is an option, go for it. Water less for now and as the spring rolls into summer, water it more frequently. Lastly, let me know if you have any further questions and I’ll be happy to answer them.