Question
My tree is probably 8-10 years old, 7-8 ft. tall, indoors. north window, grown from 12 inches tall, no problems til now. Fertilized regular, no over watering.  Leaves turning yellow and dropping off. Got a larger pot, very carefully repotted, fertilized, still in the same place, but still dropping leaves. No change in temp.

Answer
Hi Shirley,

You haven't provide enough information for me to give a specific diagnosis. For starters, it is quite normal for Norfolk Island Pines to drop older branches as they age. As long as you are getting about as many new branches on top as you are losing old ones below, then it is not a problem. So I don't know if you have a problem or not.

Excessive branch yellowing can be caused by inadequate light and either over or under watering. Neither fertilizer or repotting will solve either of these problems and may aggravate them.

If the light has been the same for the past several years or more, then that is unlikely to be the problem. In general, a north window is fine as long as the tree is close to and in front of the window and the window is completely uncovered throughout the daylight hours.

Watering is much more tricky. In general, if the tree is properly potted, it is best to water thoroughly as soon as the top quarter of the soil is just barely damp or almost dry. If the tree is in a pot that is too large (a very common problem), then inadvertent over-watering is very likely to occur over a period of time. Root rot occurs slowly and out of sight. If you have not allowed the tree to dry properly between waterings, then the roots may have slowly rotted and the tree is just now starting to show the symptoms of the root rot. On the other hand, keeping the soil too dry, will also cause roots to die back and the same symptoms will occur.

So my educated guess is that if the tree is getting proper light as I described, then improper watering is the cause of your NIP problem.

I have written articles on repotting, watering and on Norfolk Island Pine care that I will email for free to you (or anyone else) who emails a request to me at [email protected]. I have also written an indoor plant care book in a PDF format that I can sell you if you contact me at my email address.

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

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

Visit my website at: A link to HorticulturalHelp.com