Title image above is copyright © Kristi Ellinopoullos

First published 26th March 2026

The other day I lopped the top off some sugarcane (Saccharum sp.) for a customer and was taken by how similar to lemongrass (Cymbopogon citratus) the cross-section looked.

So I thought I’d grab a piece of growing lemongrass to do this very simple little photoblog!

The lemongrass on the left was cut at soil surface and laid alongside the sugarcane top — that top had been easily 2.5 m higher in the air just a short while ago!


copyright © Kristi Ellinopoullos

Both are grasses, but unlike pretty much every other grass species out there, these two we eat. They are specifically grown for their flavoursome inner stems. Botanically, a grass stem is called a culm, and that inner bit is the pith. The pith is surrounded by xylem (carries water and nutrients) and phloem (carries the products of photosynthesis such as sucrose).

Cross-section close-ups:


copyright © Kristi Ellinopoullos

They even have the same pink streaking on their leaves! Here’s a better photo:


copyright © Kristi Ellinopoullos

I think (no proof without isolating and growing a culture for proper identification) that these are possibly Methylobacterium spp. or Methylorubrum spp., otherwise known as the pink pigmented facultative methylotrophs (PPFMs). Below is an extract from where I first wrote about these:

PPFMs are bacteria which are often found in the phyllosphere (phyllo as in leaves), or the above-ground part of the plant, The phyllosphere is the opposite to the rhizosphere, which is the root area of a plant (rhizo means roots).

Breaking down the microbial terminology:
pink pigmented — caused by carotenoid pigments (a class of red, yellow and orange pigments — think coloured vegetables and autumn leaves) in the bacterial cell and believed to protect against UV;
facultative methylotrophs — optionally methylotrophic;
methylotrophic — literally ‘eats the methyl group (-CH3)’: here this really means that PPFMs can metabolise single-carbon molecules such as methanol (CH3OH), formaldehyde (CH2O), and methylamine (CH3NH2) for energy.

The PPFMs are known to form symbioses with sugarcane and many other plants. Methanol is produced by plants, a food source for PPFMs. PPFMs are able to fix nitrogen and produce growth hormones, which benefit their plant hosts.

I have never seen this growth in freshly-cut, healthy growing cane, only in dead or compromised parts from previous cuts, or in older dying canes, or in canes left on the ground for weeks.

I posit that they never are in healthy intact canes. They are facultative methylotrophs, meaning they can metabolise other foodstuffs if available. Thus I suggest that if they were in healthy intact canes, that they would present as that same pink mass throughout a growing cane, availing themselves of nutritious cane contents, and render it inedible. And I have never seen this, only in not-so-healthy or otherwise compromised canes.

However, the leaves around those canes are always tinged with pink dots and streaks all over. You may even see some of this in the above photos.

A cut cane is going to be a very opportunistic source of sugars and other nutrients for these little guys, with the leaves a vector of sorts, into that cane. Once in the presence of rich and energy-dense sucrose their numbers cannot help but explode into a visible pink mass, much like otherwise harmless skin bacteria entering a wound can feed on the internal tissue and grow to such numbers as to cause an infection.

The title photo supports what I say above as to why I suspect these are symbionts and not pathogens — these freshly cut stems are completely devoid of inner pink masses despite the immediately-surrounding leaves covered in same.

I did track down this most excellent publication on sugarcane diseases and found two that cause an internal red mass: Fusarium sett rot caused by the fungus Fusarium sacchari (p36), and pineapple sett rot caused by the fungus Ceratocystis paradoxa (p37). (Setts are cane segments used for propagation — think cuttings.)

For what it’s worth, I have only ever seen pink internal growth on canes cut ages prior, never immediately on cutting. Cutting would provide the means for PPFMs to access the inner tissue, and it is always on the periphery, not in the centre as with those fungal infections.


copyright © Kristi Ellinopoullos