The three reasons that I am aware of for yellow leaves are: (1) iron chlorosis, (2) sunscald and (3) nitrogen defficiency. If the leaf veins remain green while the rest of the leaf turn yellow (white in some cases) then it is iron chlorosis. If the whole leaf turns yellow then the plant is getting too much sun. You need a soil test to check for the third one.

Water and drainage issues can lower the pH of the soil where the water tends to accumulate. If left unattended for a long time, lime and salts may accumulate in there too.

Is the tree located in a low point?

Lastly.... if the leaves develop yellow areas (so it is not a case of the whole leaf turning yellow) then that could be a sign of starting powdery mildew. And a host of fungal infections will cause yellowing but you would have noticed spots on green leaves before the leaves turned yellow and dried out.

PS - Can you post pictures? Someone may get ideas if you can show the area where the tree is growing as well as the top/bottom of a yellow leaf.

Hi Luis,

Thank you so much for the very thoughtful and informative response. I really do appreciate it.

You know, the leaves that turn yellow would be completely yellow. So I guess it is not chlorosis then. They are the much smaller leaves that are at the base of the stems and definitely not the main ones at the top growth. There is no evidence for any infection. The tree and the other leaves look very healthy indeed. It does get quite a bit of afternoon sun there, and not once has this tree wilted at all.

Let me show you a photo from 6-1-08, shortly after the tree was planted. I must say that it is now much fuller and larger. As you see, it is in a sloped area. The soil is heavily clay, but I dug a big hole and amended it with garden soil. Also, I placed the tree quite a bit higher than the ground level for improved drainage:

So I wonder if you have any further suggestion, Luis? Thanks again!

Clay soil sometimes creates problems because it does not drain well and the ammended soil ends up collecting water from all the sides where the ammened soil contacts clay soil. It is sometimes called a bath tub effect. The bath tub represents the hole that we make and which we fill with ammended soil. Then water from all clayish sides eventually seeps into the good/ammended soil.

This does not seem to be a big deal for the other shrubs though. Puzzling...

Hi - Here's my 2cents - I have noticed this occurrences with many of my bushes & perennials, particularly when they are exerting a great deal of their energies, into the show that they are putting on, be it - filling-out with thick & tight foliage or flashing blooms. Even my Pear & Crabtree do drop some yellow leaves (perfectly beautiful but smaller ones, usually). Among the bushes & perennials I notice that the yellow leaves are mostly from under/inside areas that perhaps get too dark & not getting the benefit of the sun - they eventually drop & life & their shows go on!!!

Now if the ensuing yellowing problem gets severe ... I think you will know & follow the courses suggested by Luis.

From you photo I can't see the yellowing too well ... the yellow leaves I get are truly banana yellow as if the leaf just ripened & eventually will drop. BTW your SM looks great! Oh & what is the variegated little bush to the right, is it Cornus Alba? I just got one on Mom's Day & love her (George convinced me to look at one ... said nicer investment than my Mariesii Var.!!!)

Good luck on your SM dilema, I hope it is just an adjustment situation, since she is newly planted. BTW I just watered this AM & little Princess Kyu has a few yellow ones inside her very fully foliaged & clustered head!!!

Hi luis, I am worried about the heavy clay too! I actually specifically made sure that I mixed the native clay in with the amended soil, so that there would not be a distinct water barrier between the amended soil and the clay... I hope this was not the case here! Sigh... I will keep watching.

Hi ditas! Yes, I think that you do have a great point there. It's really only the smaller, inner leaves that turn completely bright yellow. The entire leaf including the veins. Anyway, This lovely tree is really otherwise doing well. Let me show you a photo that I just took this evening:

Look at how much fuller it is, comparing to just 3 weeks ago!? Now, the varieted perennial to the right is actually lysimachia punctata Alexander. I love it! It's so pretty with the yellow flowers. I hope that it will get a bit larger, but it's only its second season as it was planted last summer. I am so hoping that the geranium Jolly Bee will bloom more vigorously when summer really gets started, so that there will be a nice contrast between the blue/purple geranium blooms and the yellow blooms of the lysimachia :-)

Oops, I got off track here... LOL

To my eye your JB is vigorous enough :-)
I would be much more concerned about its placement than a size cause in a short two years Annabelle without division will be about twice wider.
What is in a right corner? Isn't it an anemone tomentosa 'Robustissima' by any chance? If so, you are in a big trouble-this thing will eat alive anything in this bed except two hydrangeas.

WOW! George, you have very good eyes! Yes, it is an anemone, but it's Anemone hupehensis 'September Charm' - now, is this much different from anemone tomentosa 'Robustissima'? I love this plant so much though that I took the risk... hmm... maybe I will regret it later! LOL!

The Annabelle in the corner is already several feet wide. It is in its 3rd season. The trunk of the SM tree is at least 8 feet or so from the deck.

All anemones, including Sept.Charm, given the right conditions (which seems you provide) could be somewhat agressive, but still containable.
Contrary to that, Robustissima is a thug which sends shoots 3 to 4' out of the mother plants via root runners and eventualy take the whole space.
IMO, your SC could easily find its place in the kidney bed, but now is not the right time to move it, so wait till next spring.
Re: Jolly Bee. I'd rather see it as an underplanting for SM-tree (or in a kidney bed, again) than being swamped by ever-increaing Annabelle. BTW, in my garden all JBs performing much-much better than Rozeannes, but I can't find them anymore.

Hello, ostrich. How is the hydrangea tree doing and have you noticed any changes?

I was thinking the other day about this problem and wondered if this area where the tree is planted may have buried trash from house or gardening construction projects? Have you ever come across that stuff when planting any other nearby shrubs?

Another question: do you have black walnut or butternut trees in the landscape? These trees release juglone, a substance that is toxic to some plants, mostly through the roots. The toxicity area covers from 50-80 feet off the main trunk. New plants show signs of trouble within 1-2 months of being planted.

George - thank you - I think that the idea of underplanting SM with JB is wonderful! I will do that next spring. For now, I just want to make sure that my SM will live!!! :-)

Luis, thanks for your follow-up and thoughtful post. There is no buried trash or anything like that there. The nearby shrubs (Annabelles) are doing great! So it's very weird... since I live next to a ravine, I can't tell what is there, but I am not aware of any black walnut or butternut tree there. Now, it seems like the yellowing has slowed down a bit... we have had some warm and stormy weather over the last few days, and it seems like there is more new growth too... so I am keeping my fingers crossed and see what happens!

Thanks again to both of you!