Question
I have had a large healthy, until now, Yucca plant in my conservatory for over a year now.

When I returned from holiday I noticed lots of large brown spots appearing on both old and new foliage which was previously healthy. The spots are increasing in size but are not raised and do not appear to be fungal.

I know that watering was erratic whilst I was away and also the metal container that it is planted in has developed rust spots.  

Any ideas on whats wrong please as I am losing a beautiful plant!

Answer
Hi Jane,

The brown spots you describe are what Yuccas do when there is a problem with their roots. It could be improper watering - both under and over - or poor quality water or roots wandering out of drainage holes or excess minerals in the soil surrounding the  roots.

The fact that the new leaves are also affected means the problem is more serious and more likely to be over rather than under watering. In fact, it may be that the roots have already started to rot. Yuccas must be allowed to dry out at least a third of the way down into the soil unless they are very rootbound and in very strong light. IF the pot is too large for the plant, then that will also lead to root rot. If the root rot is not too advanced and you get the watering back under control, then you may see a gradual improvement in the new leaves that emerge. The already spotted leaves will not restore themselves.

If your water is on the hard side, then use filtered or distilled. If you are fertilizing regularly, then stop. If there are roots wandering out of drainage holes, trim them off. If there are no drainage holes, then that is the likely cause of the problem.

Metal planter were used at one time, but are no longer because of the mineral elements that can leach from them and damage the roots. That yours is rusting is an indication that the metal may be contributing to the problem.

I suggest that you unpot your Yucca so you can replace the metal planter. Inspect the soil and roots. If there is a mass of soggy soil and soft, mushy, dark, roots, then root rot is the problem. (If there are no healthy roots, discard the plant). Remove any loose soil from around the outside of the rootball. Try to reduce the size of the rootball by removing as much as possible without exposing the roots unnecessarily. Replant it in a pot that is barely large enough to fit the slimmed down rootball.

I have given you a ot of information here so 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

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