This is my first year trying seedlings, and I have some leek seeds about a week and a half in. Around 20% of the seedling containers have green discoloration to the soil. It doesn't look fuzzy at all, just a greenish colour like I'd dropped in some food colouring.

Should I be worried about this? Is it fungus? I used seedling starter mix and there's a cover to the seedling tray, but there are fungus spores everywhere so I could definitely believe there is some contamination.enter image description here

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1 Answer 1


Most likely algae; should not be a problem.

  • Yes, algae, caused by excess humidity under the tray cover, rather than a fungus. I've seen this on my own seedling trays when I used rather poor seedling potting soil, over-watered the trays, and didn't take the cover off soon enough. It's a problem only when it grows thick enough to crowd out the seedlings. You can manually remove it by gently prying it up if that's going to be a problem.
    – Jurp
    Mar 10, 2022 at 13:19

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