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Extrafloral Nectaries (EFNs) on Philodendrons

  • Writer: Lynn Adkison
    Lynn Adkison
  • 7 days ago
  • 2 min read

What is that spot on my plant? Is it a bug?!

Blind panic sets in and I immediately start thinking about how in the world I'm going to quarantine this ONE plant (or has it spread already) when I only have JUST ENOUGH grow lights for everyone in the current setup. I definitely don't want this plant to wither away without enough light, but I also don't want every other plant to "catch" whatever it is this one has...


Wait...it's not moving. And it's...sticky? Maybe it's honeydew (icky, sticky pest waste)?


A mad plant inspection ensues, and it's not long before I realize that there aren't any other signs of bugs. Hmmmm, what IS that?


The plant in question is a philodendron - specifically for me a P. Joepii - and it's covered with sticky spots, brown spots...spots. Everywhere. They're all over the petioles and midribs, there are even some on the leaves. What is HAPPENING right now?!? To the interwebs we go!

Nifty science facts I learned: EFNs are external (meaning outside of the flowers) glands. Those glands produce nectar, which then acts a food source for bugs (usually ants). In return, the bugs (ants) act as a paid security detail for the plant, keeping them safe from herbivores (animals that eat plants). So it's symbiosis - a symbiotic relationship - mutually beneficial for the plant AND the ant. I got excited. (NO BUGS - YAY!) I wanted to explain this better, so, I compiled a delightful pictorial illustration of the situation.


Illustrated guide to Philodendron Extrafloral Nectaries (EFNs) showing the symbiotic relationship between plants and ants. Highlighting how rare tropical plants use nectar to attract security against pests. A Curated Cuttings Flowery Branch GA original.
Illustrated guide to Philodendron Extrafloral Nectaries (EFNs) showing the symbiotic relationship between plants and ants. Highlighting how rare tropical plants use nectar to attract security against pests. A Curated Cuttings Flowery Branch GA original.

The "Science is Nifty but Requires Explanation" Section:

  • Extrafloral Nectaries (EFNs): The star of the show. Nectar glands located outside of the flower (usually on the petioles or the leaf backs).

  • Symbiosis: The relationship where the plant provides "sugar water" and ants provide "security" against pests like caterpillars.

  • Petioles & Midribs: The specific "geography" of where these spots usually appear.

  • Secretory Cells: The microscopic "engines" that produce the nectar.

  • Honeydew vs. Nectar: Honeydew is pest waste (sticky/gross); Nectar is plant-produced (sticky/cool).

Relax, Lynn, This is NORMAL

Apparently, perfectly healthy philodendrons of all sorts - not just my P. Joepii - get EFNs. It's absolutely normal if your plant has some too. Just keep an eye on it. There are some instances where EFNs show up because your plant is stressed, so if you've got a plant that doesn't normally have them, and they just show up out of nowhere, it could be there's something (else) wrong.


But the EFNs? They don't actually cause any harm. They just make spots from the crystallization of the sugar in the nectar. In fact, they could be even more sticky and noticeable in summertime, when the NE Georgia heat and humidity kicks in - I guess that's just part of the 'philodendrons in Zone 8A' charm! There, now I feel like we've all had a 'The More You Know' moment.

 
 
 

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