Verbena and Lemongrass molding, why?

Hello everyone,

I recently started propagating verbena, lemongrass, and rosemary cuttings. Really excited that the rosemary is thriving I see roots, zero mold, and it’s ready to be potted. The lemongrass and verbena have developed tiny little roots but there’s mold on the stem right above the roots or waterline. I’ve been cleaning the cups that hold them and changing the water every 2 days. I put in a little less water to not drown them and clean the mold off but days later there’s mold again. I’m in SoCal(zone 10a), it has been really hot lately. Is it the heat? Has anyone else dealt with moldy stems while rooting lemongrass or verbena in water? How did it work out for your plants? Really appreciate any suggestions you share to save these stalks.

That might be powdery mildew since it has been a rainy season, maybe?

The forum has some non-toxic fungicide recipes that work well.

Please try them.

Verbena definitely is affected by powdery mildew, I was just noticing some on mine in my garden this morning (it is a very wet winter where i live right now and it will pass, so I'm not too worried).

On cuttings in water that's usually not powdery mildew, it's just regular mold that loves the moist conditions right at the waterline. Changing the water every couple of days is good but you could also try adding a tiny splash of hydrogen peroxide to the water, it keeps things cleaner without hurting the roots. The other thing that helped me was using a narrower vessel so less stem is exposed to damp air above the water. Perlite or vermiculite in a cup works well too if you want to get away from water propagation entirely, holds moisture without everything sitting wet.

Aww, thank you all! These are great tips to try out. Definitely adding them to my lil garden book.

Aurora Maville wrote:Hello everyone,

I recently started propagating verbena, lemongrass, and rosemary cuttings. Really excited that the rosemary is thriving I see roots, zero mold, and it’s ready to be potted. The lemongrass and verbena have developed tiny little roots but there’s mold on the stem right above the roots or waterline. I’ve been cleaning the cups that hold them and changing the water every 2 days. I put in a little less water to not drown them and clean the mold off but days later there’s mold again. I’m in SoCal(zone 10a), it has been really hot lately. Is it the heat? Has anyone else dealt with moldy stems while rooting lemongrass or verbena in water? How did it work out for your plants? Really appreciate any suggestions you share to save these stalks.

It sounds like you’re doing a lot of things right, and it’s great that the rosemary is taking off. The mold on the lemongrass and verbena may be from the combination of warm temperatures, stagnant humidity around the waterline, and plant tissue staying constantly wet.

You might try changing the water a little more often, keeping the water level just below the moldy area, and giving the cuttings a bit more airflow. If the stems are still firm and the roots look healthy, I wouldn’t give up on them yet. Sometimes they can recover once conditions are adjusted.