Black area on monstera leaf after week on holiday

Question

As the title says, I’ve just got back from a week’s holiday to find a rather large black area on one of the leaves of my monstera. I watered it before I left and ensured it still had some sunlight.

Does anyone know what this might be? As you can see from the photo another leaf has a small brown area too, however this hasn’t got larger and has stayed the same for some months now.

I should mention the plant is still putting out new leaves. The affected one is at a bit of a weird angle compared to the other so apologies for the odd photograph.

Answer 1

We might try to think about these patches from the cell level. The leaf consists of an outer top layer of hard cells and a lower underside layer of equally hard cells and sandwiched between is a layer of much softer cells which do a lot of the chemistry processes, air exchange, purging of excess water and so on. When cells are damaged by high heat or other means that cauterizes the wound then this effectively seals off the neighbouring cells from any infection. On the other hand, if there is a crushing damage to the leaf that leaves cells, particularly those in the interior of the leaf bleeding sap this can be a point of infection which then spreads through the inside of the leaf in all directions even into intact cells which bleed out leading to the black patches. Eventually the leaf cells will re-establish control but not until after the damage has spread fairly widely.

Try to think back to see if your plant was against a very cold window or received a crushing event like being squeezed between a rock and a hard place.