House Plants/norfolk pine
I have a 25 year old norfolk pine that I transplanted into a bigger pot about 2.5 years ago. Since then it grew and looked the healthiest it has ever been. All of a sudden the fir branches started turning yellow and dropping at an alarming rate. Since I have not changed it's care, I investigated the soil in the pot and found huge hard clumps that are not absorbing any water. So now I am planning to repot. This time I will mix potting soil, sand and peat moss. But I am thinking of getting one of those tall pots you see in malls with trees in them but my mother says they need wide pots instead of tall. Any thoughts or advice?
Based on the information you have provided, it is hard to determine just what has caused the recent branch yellowing. However, I can assure you that changing the pot will not remedy the situation.
Sometimes plants react adversely to repotting, but your last repotting was 2.5 years ago, so that is not the cause. If it has been receiving the same light throughout, then that would eliminate changed light as a possible cause. You didn't mention any pests so I assume that spider mites and mealybugs are not an issue here. That pretty much leaves watering as the source of the problem, unless it was recently exposed to a sudden change in temperature or a foreign substance added to the soil.
Presumably, the hard dry clumps (of I assume peat moss) presumably were there since repotting, so I cannot think of a reason why they would now pose a problem. I don't recommend repotting, but any clumps that are easily accessible without disturbing the roots should be gently broken up and left in the pot.
Watering Norfolk Pines can be tricky, especially after repotting. Even a single instance of allowing the soil to become too dry can cause sudden yellowing. On the other hand, keeping the soil just a bit too moist without proper drying can cause slow and imperceptible root rot that does not show its effects for a very long time. I suspect that may the cause of the problem, but I do not have enough information from you to be sure. If the pot is over sized or does not have drain holes, then root rot is even more likely.
Remove any soil on the surface that is not in immediate contact with the roots, as it serves no useful purpose and can prevent proper drying out in the root zone. Then, water only when the top half inch of remaining soil feels dry. Apply just enough water so that it reaches that same level of dryness again a week later. You will have to experiment to determine just what that amount is.
Unless you can provide me with additional related information, that is the only advice I can give you right now and that may be all you can do.
I have written detailed articles on repotting and on Norfolk Island Pine care that I will email for free to you (or anyone else) who emails a request to me at wcreed@HorticulturalHelp.com. 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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Will Creed, Interior Landscaper
Horticultural Help, NYC
Visit my website at: http://www.HorticulturalHelp.com