Orchids are definitely weird. (A friend of mine calls them "creepy") They're so weird, they can die of dehydration even though they're being watered adequately and are in damp or wet soil. (Well, potting media, really, not soil, although I've seen the phalaenopsis orchids commonly for sale at home centers and grocery stores potted in soil. More about why that's a bad idea later on.)
Right now I have an orchid rescue from my mom. I took in her sick phalaenopsis, and gave her one of my healthy ones. Here's the sick one, freshly repotted. (I'm showing you the "after" first, see.)
Poor thing. It was a gift to my mom from my brother and his wife. It's very pretty when in bloom! Hopefully, I can nurse it back to health and in a year or two I can give it back to my mom. This is what I found when I pulled it out of its pot: completely saturated sphagnum moss and all those black lines, which are rotted, dead roots. The potting media was definitely not dry. Surprising, right, given that the plant above looks like it's drying up and wilting? The answer is in those roots.
Orchids (and here I mean, "most orchids generally available in regular stores", which are nearly always phalaenopsis, not orchids you order from specialty growers, some of which require entirely different growing conditions) do not like wet roots. At all.
If the roots stay wet, they rot and die. Period. And sphagnum moss stays wet a long time. Dead roots = dehydrated plant. I suspect that orchids sold for mass retailers are packed and shipped in sphagnum because it's 1) cheap and 2) it gives enough moisture for plants to survive hot trucks, warehouses, and general neglect while in transit and in the store. But it's not a very good long term potting media for most orchids.
I pulled away all the dead and rotting roots and trimmed back roots that were about to die and this is what I was left with. On the right, the sicko orchid. On the left, a healthy phal with plump, healthy roots.
There wasn't much root structure left when I was done. The aerial roots on the top were mostly ok (they're silvery and whitish, which is fine, and they're not wrinkled and dry looking), but there was almost nothing left of whatever had been in the moss. I repotted it in bark mixture and made sure it was nice and secure and now it looks like my first photo up above.
Some more root pictures for you, using two miniature phalaenopsis orchids I picked up today. First, super-saturated, but still healthy (probably not for long; see the standing water in the pot?) roots. See how they're green and fat?
Here's the other miniature phalaenopsis I got today. Its roots are in the danger zone. You can see some healthy, plump, and green roots, but there are some that are wrinkled and fading.
Note that roots turning silvery and grey, but not getting wrinkly or soft, simply means they're dry. You can go ahead and water. It's the wrinkling and getting soft and squishy that's bad.
Now here's your reward for listening to me try to rescue those poor big-box store orchids that go home with so many people, only to die a slow death and confirm everyone's mythology about how "hard" orchids are to grow: teensy tiny phalaenopsis orchids! And both fragrant! Woo hoo!
The plant on this one is super healthy, with two flower spikes, two new leaves starting and several bright green root tips showing. Its lower root system is not that great, though. It's the one pictured above as being in the "danger zone." I'll repot as soon as its done blooming, and in the meantime, I will need to water veeeeery carefully in order to prevent drowning.
The other one is sort of blah colorwise, (pink and white, yawn) but the fragrance is beautiful. Not overpowering, though. You'll only smell it if you put your nose right in the flowers.