Old leaf tip turning tar black?

[Dante1709]

I've had this ventricosa for almost a year now, and it's been doing great. Two lower leaves are yellowing, and I first thought it was just age. A few days ago, however, I noticed that the oldest leaf has a very dark tip to it, as if someone covered it with charcoal dust. All the other leaves look unaffected, but I'm just scared that this is root rot or burn.

I have it in 50% humidity, 77F days and 73F nights (sometimes the day temps can go up to 80F, if I bring it outdoors). It's potted in a bark/spaghnum/peat mix, and I usually water until the top of the moss is pretty dry. No fertilizing, and I water with rainwater. It's in medium sunlight (around the same lighting Oncidium orchids like)

Here's a photo :
Untitled by Dante1709, on Flickr

Is this just the natural aging of the leaf, some type of fungus or root rot? It happened pretty rapidly (within a week, at the most) since I haven't noticed it before.

 

[Bio]

Completely normal leaf die-off. Nothing to worry about.

 

[morbus]

its just normal ageing
im told that dead leaves can cause fungal problems, but thats not something ive had a problem with. If you are concerned, you can cut the yellowing/black leaves off.

your plant is fine!

*edit* Bio beat me to it

 

[Dante1709]

Oh, thank goodness. I just thought it was odd how it transitioned so quickly, and from yellow to dark black. What would root rot look like,though? I've heard that it starts at the growing tip, but then logic tells me it would start from the base, and I've always been curious about it.

 

[Bio]

Root or stem rot would spread from the base of the leaf outward, and spread from the bottom to the top of the plant. I would only worry about dying leaves if they were dying from the center out.

 

[theplantman]

Normal but it shows symptoms consistent with nitrogen deficiency. You can extend leaf lifespans with consistent feeding, and make your plant create/sustain more leaves overall.

Root rots vary in symptoms but a general one is wilting, because the connection between roots/leaves is damaged. Wilting usually precedes color changes.

 

[PsychoSarah]

Considering all the leaves you have which are perfectly fine, I wouldn't be concerned.