What Causes Yellow Needles in the Spring?
This is Part II of last month’s post, Rain and Needle Size…
…as rain is again the likely culprit. Or possibly, overwatering with the hose.
This Black Pine’s needles are yellower than they should be, the result of an overly wet Midwest spring.
In the post about rain and needle size, a correlation was drawn between unseasonably wet springs and long pine needles. Another indication of too much rain (or overwatering) for a pine is that the new spring needles grow out yellow.
The solution to this problem is being sure that watering is withheld until it is clear the tree is drying out a bit (about 70% dry is a good way to think of it.) Also, don’t neglect the fertilizer. Doing both these things can green up yellow needles later in the season. Last year’s needles, if yellow, are harder to green up.
Michael Hagedorn 
5 Comments
Man, am I glad my trees are in a hoop house during the winter and, especially, in Portland this year.
So, after the soil dries out and fertilizer given, the new cells will be more greenish and as the cells turnover in the yellowish needles, the new cells replace them, thus the gradual color restoration?.
The challenge is placing pines in a position to protect them from too much rain.
Thanks for the info Michael. On a perhaps more serious pine problem: I have what appears to be the beginning of pine wilt on a 40yr + Scots pine bonsai. I lost a nice witch’s broom Virginia pine to the same ailment. Needles turn gray, then brown on individual branches and progress along the tree. The roots appear normal and healthy. I suspect it is nematodes in the zylem. The literature says there is no hope once the tree shows symptoms. Do you have any experience with pine wilt in bonsai?
Thanks,
Jim
I can see it has needle cast as well. Pines also benefit from a biannual application of Chelated Iron in vitro. Only way to truly know what is happening is to do a controlled study.
Good timing with this post. Here in NY, it has been an exceptionally wet spring. I am noticing yellowish needles on one or two of my black pines. Should this have any impact on decandling? And if not, will new needles after decandling be greener if rain slows down and watering is more controllable? Thanks.