The Q&A Archives: Mold On Seedlings

Question: I'm starting my vegetable garden indoors from seeds. Lately, I've noticed green mold developing on the surface
of the flats. I understand that its caused by moisture from watering but can that hinder the growth in any way and more important, can it be stopped without damaging the seedlings?

Answer: Generally that slimy green stuff is caused by the soil being kept too wet and by (possibly) lack of air circulation. If you are waiting for your seeds to sprout, the best way to maintain humidity is to plant the seeds into barely damp soil, then encase the pot in clear plastic. Set it in bright light out of direct sun and wait until they begin to show. At that point, remove the plastic and begin watering lightly. The seedlings should not be allowed to dry out, but they will also rot if kept too wet. The pots should never sit in a pool of water or be left sopping wet. Try for the soil to be as moist as a wrung out sponge. The larger the plants grow, the more water they will use and consequently you will water more heavily. Once your watering is more in proportion to what is actually needed, the growth should stop and I don't think it will harm your plants. If the seedlings are very late to emerge I might be a bit concerned that they have been kept too wet, however.

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