Dendrobium: black leaf tips, then spots and yellowing
 

Hi,

I'm a total beginner in plant care. I've got this orchid, which I assume is a Dendrobium phalaenopsis. The tips of the leaves on one of the stems have started going black. The colour spreads into the leaf gradually, and small black spots appear. Then the tip starts yellowing. What could be causing it?

Could it be temperature-related? Before I spotted this problem, I'd left it next to an open window a couple of times, and it'd been quite cold out.

Thank you.

It could be cold but, it's most likely lack of water. These like to be moist.

there are too many factors that can cause this including low temps, high temps, wrong ph, too much fertilizer, degrading substrate, too soggy substrate etc.

When looking after orchids you should be aware of their temperature tolerances depending on what variety you have, then you need to be aware of what the roots look like when you first get the orchid - this involves a repot. A good quality substrate should be on hand if the old substrate needs replacing.

Feed it rain water over tap water to avoid ph issues.

Pick large chunky Substrate that dries well and supplement it with more water retentive substrate if it dries too fast but keep it airy and slightly moist at all times over soaking wet. I'd recommend reading some basic care guides on the topic.