Microgreens getting damping off (I think)

11 years ago

Hey folks,

It looks as though my microgreens are getting damping off. It has been particularly hot here in Northern CA recently so I may have been upping the water too much. Here is a breakdown of the process I use to grow the microgreens (I currently have: mizuna, mustard mix, shiso, cilantro, arugula, basil, and pea shoots. whatever is affecting the greens is mostly targeting cilantro and shiso, although all have been affected to some degree)

My soil mix is this: a locally sourced soil blend that has forest mulch, loam, organic compost, red lava rock, delta sand, aged chicken manure, 7-5-7, gypsum, bloodmeal, Peruvian seabird guano, worm castings, and oyster shell flour.

I then add some compost, a little bit of happy frog fertilizer and lastly vermiculite.

The soil mix is misted in, seeds are sown, seeds are lightly covered with soil, then misted in again (lightly) and covered with bottom trays to retain moisture. I then put them in the garage for a few days until they germ. I mist them twice a day in the garage. Once they've germinated I bring them into the greenhouse before they get too leggy. The damping off seems to be taking place once they get to the greenhouse, although perhaps it is already starting when the seeds are in the garage.

Anyhow, which steps in my process seem problematic? From the soil mix (should I go soilless) to watering, to covering, etc...What am I doing wrong. How should I keep the top layer of soil moist without overwatering when it gets so darn hot in the greenhouse?

I've included some pics below to verify whether it is damping off or not

Thanks in advance for any advice.

shiso

swiss chard (not microgreen)

pea shoots

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Comments (8)

kimmq
11 years ago
Damping Off is most common in wet or poorly draining soils and the fungi that causes Damping Off (there are several) like wet. Damping Off can occur in soilless mixes as well as garden soil so your soil mix will have little to do with the problem.

Are the seedlings watered from overhead or are the trays put into a water bathy and watered from below?

Perhaps this article will be of some help.

http://pss.uvm.edu/ppp/pubs/gd9.htm

kimmq is kimmsr
marketgardenernorthernca
Original Author
11 years ago
The seeds are misted overhead on a timer. I have the timer set for four times a day, for one minute at a time. This may be excessive but the greenhouse gets very hot. Thanks for any more advice you could give.
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floral_uk z.8/9 SW UK
11 years ago
last modified: 11 years ago
You are keeping the surface of the medium constantly damp while not ensuring sufficient water deep in the mix. You can see that your seedlings are rooting on the surface and not growing down into the mix. Try watering either from below or much more thoroughly but less often from above. Find another way to keep the plants cool such as shading. As it happens I am sitting in San Fransisco airport writing this and I have to ask why they are in a greenhouse at all given the temps where you are.
MrClint
11 years ago
Microgreens are planted densely and therefore have specific requirements in order perform well. For starters you need to lower the pH of your water (I use vinegar), utilize a more inert type of media (I use plain coir), and provide some resistance (another tray inside a sprouting tray works fine) for proper rooting. Seeds need to push against something for a day or so to get good and anchored.

There are so many good resources out there that you should be doing it right in no time. This video is as good as any and better than most:

Here's one of my radish trays:
peter_6
11 years ago
The only sure answer to damping off is a cheap fan. This keeps the plants in motion, as they would be outdoors, where damping off seldom occurs. Regards, Peter.
floral_uk z.8/9 SW UK
11 years ago
peter-6 I have never had damping off and have never used a fan so I disagree 'it's the only sure way'. If watering is done properly damping off need never happen.
peter_6
11 years ago
floral: I agree to this extent -- watering of seedlings has to be done from the bottom. I favor hand-made newspaper pots in which water wicks upwards just fine, thereby avoiding soil compaction that results from over-head watering. But I stick to my guns that anyone prone to damping off would remove the problem with a cheap fan. Regards, Peter.
MrClint
10 years ago
@peter_6, seedlings aren't the same thing as microgreens. Microgreens are grown in solid bottomed trays or containers, there are no drain holes so there is no way to water from the bottom. Fans aren't needed in the process of starting seeds for planting or for harvesting as microgreens. In both cases the proper growing media is required, and was not used by the original poster. Adding all that fertilizer to a seed starting mix is unneeded and most likely the cause of the seedling failures.

The original poster has most likely moved on, but I thought it might help to clarify.