Yellowing Cotyledon Leaves...Why?

10 years ago

I originally posted this in the Vegetable Gardening Forum, but perhaps this forum could offer further insight/advice:

This week I've noticed that the cotyledon leaves on all my cole crops are yellowing (kale, cabbage, tatsoi, pak choy, and broccoli). They were transplanted out into 8" raised beds using the square foot system two weeks ago and were looking great until recently. They now have about two sets of true leaves that are looking lovely, but the cotyledons are yellowing and I don't want it to get worse.

The soil mix is 1/2 organic compost, 1/4 vermiculite and 1/4 peat moss (give or take). Since there are a lot of nutrients in the new soil mix I doubt there would be a nitrogen issue, but do correct me if you think I could be wrong.

We had a ton of rain last week and cold temps but the cole crops were proected with row covers which were removed the following morning. Now it is in the upper 70's, low 80's and sunny this week. Could they be in shock with the sudden transition?

On another note, I kept a few "extra" seedlings from thinning and transplanted them into small pots filled with potting soil for friends. Those plants look great with no yellowing, which leads me to suspect it is a soil issue in the new raised beds. Do you think I need to add an organic fertilizer or some additional type of supplement and if so, what might I try?

I'd love and ideas or advice, since this is my first year attempt at raised beds and don't want to lose my little seedlings!

Comments (3)

  • nanagarden
    10 years ago

    I would add fertilizer. I was taking a gardening class with a friend and the lecturer (who was a long time master gardener) told us to never buy transplants with yellowing Cotyledon leaves. He stated that when the leaves yellow the plant is using its energy reserves to survive. (I don't know if this is true or not but that is what we were told)

    While I rarely use fertilizer, I would in this case to help the plants.

  • susancol
    10 years ago

    It is completely natural for the Cotyledon leaves to die once the new leaves take over feeding the plant. The Cotyledons are there to feed the plant while it's developing it's first roots and leaves. When it's job is done it dies off because the plants don't need them anymore.

    Never buying transplants with yellowing cotyledon leaves is good advice because for transplants, most of the time a younger plant will do better for you than one who has spent too much time in the cell pack. Too much time in the cell pack results in root bound plants that will not grow well, or if you try to break up the bound roots, then you break the roots which stunts the development as well. (Although you are better off breaking up the root ball than leaving it bound up.) A young plant won't have these troubles and will size up quickly once planted in the ground.

    Hope that helps!

  • Cosmo Dawn
    2 months ago

    Totally normal if all of the other leaves on the plant are green and healthy it's nothing to worry about these leaves aren't true leaves and they're only meant to get the plant started once the plant starts to get more of its own true leaves a lot of times it will stop putting its energy into those first leaves which will then cause them to yellow brown and fall off. Mine always do as long as the rest of your plant looks healthy you have nothing to worry about. I don't know about all of the plans but I do know broccoli in particular are heavy feeders and do require a lot of nitrogen so if you just transplanted them you might want to give them a little bit of fertilizer but don't stress out the coating they're meant to die eventually.

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