I started this oregano from seeds in August. It was flourishing and doing very well until the past two weeks. I noticed some grayish leaves near the base of the stems but thought nothing of it, and now they are all over. It seems to start with the edges of the tip of the leaves turning brownish, shortly the leaves are completely overtaken and are so brittle and dry they just fall off to the touch. the main stem does not appear to be wilting or damaged in any other way besides a lack of leaves where the dead ones have fallen off. I have searched the plant for bugs and have found none. There is still new growth coming up on the stems. Can anyone help me identify what the problem is, and what to do to save the plant?
no, i usually let it dry out quite a bit before i water b/c i had fungus gnats for a little while during the end of summer. i water it about once every four or five days. when the topsoil is dry to the eye and touch.
When you say that the topsoil is dry to the touch, are you just touching the surface or do you stick your finger down a few inches? The top of it can look/feel dry when an inch or two down where the plants' roots are is still quite wet. To me it looks like a fungal problem of some sort, and too much water would be a likely culprit.
If the soil is really wet then repotting it in some drier soil may help too. Hard to say if it will recover or not--it doesn't look too bad so I think chances are good, but it really depends on how badly the roots have been damaged already.
We have heat registers out here with built in shelves over the top. My orchids, aloe and parlor palm love sitting on top of it b/c it's so warm and dry. Maybe if I put the oregano over there it will dry out. Is this problem contagious? I definitely don't want to put those other plants in danger. (Sorry if these are novice questions, I'm new to herb growing.)
Assuming it is overwatering that is causing the problems, it isn't contagious and won't spread to your other plants (unless you're watering them too much too, in which case they could have problems as well but it won't be because the oregano is near them). As far as sitting on top of the register, as long as it's not so hot that it cooks the roots it should be OK. You also want to make sure that hot dry air isn't blowing directly on the plant, that can cause problems too. But it sounds like air wouldn't be blowing on it with your setup?
There is no air blowing from the registers, just heat radiating up. The shelf surface is marble, and stays warm all of the time but not hot to the touch. I just put a strip thermometer on it and it stopped at 78 degrees F. The only circulation comes from the large window behind the plant, which I only leave cracked open from the top about two hours a day to prevent mold in the house b/c it is so damp here in the wintertime. Should I put a fan on it too maybe?
Air circulation is great for plants in general, helps them use the water in the pots, and keeps them from being weak because they have to strengthen to resist the wind and stay upright. 78 F is a great temp for roots of tropicals. If you trim it, don't remove healthy leaves. They are the food factory of the plant.