Question
About two weeks ago I repotted my Yucca plant.  I did this because one of the two plants was infested with scales.  I separated the two plants, threw away the sick one and replanted the healthier one.  I also sprayed it with insectisied to prevent any scales from growing on this plant.  I have now noticed that the bottom leaves of the Yucca are turning yellow.  The plant recieves direct sun light for about five hours every day.  The Yucca is in is an 18 inch pot with Mircal Grow potting soil.

Answer
Hi Samantha,

Your Yucca is reacting to the stress of division and repotting. In addition, I am sure that the roots are beginning to rot. Here's why:

A single Yucca should be in a much smaller pot; the smallest pot that the roots will fit into. The extra soil that is added to a too large pot acts like a sponge and stays wet for too long. This deprives the roots of oxygen, which they need to survive. In addition, Miracle Gro potting soil is too heavy and contributes to the problem.

I suggest that you unpot the plant, remove the extra soil that you added, leaving just enough soil to surround most of the existing roots. Then put that slimmed down rootball into a pot that contains the rootball snugly, probably an 8" or 10" pot. Fill in the empty spaces with two parts of a peat-based potting mix and one part perlite.

Water your Yucca thoroughly and then don't water it again until the top 2-3 inches of soil feels dry to the touch. Keep it in a sunny location.

It may take a couple of months for your Yucca to recover from all of this trauma. Also, you should be alert for early signs of scale. There is a good chance that immature, less visible scale insects are on this plant, as well as the discarded one. If you find more scale, let me know and I will explain how to treat it.

Please let me know if any of this is unclear or if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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