Early Yellowing Foliage—What Does It Signal?

Fall is a great time to sit back and assess our bonsai triumphs and misdemeanors. Often by summer’s end we see branch weakness or loss. And we might wonder, ‘What is it? And how much of that is my fault?’ 

You might notice a branch on a maple that turns yellow weeks before the others. Or one that loses leaves sooner than the others. While the sun side of a deciduous tree may be more colorful than the shade side, take note of leaves turning color randomly.

In short, these are on the weak branches. And they are flags.

A Holly with yellowing interior leaves. These leaves indicate shoot weakness, turning color well before the exterior leaves. Consider cutting exterior leaves in half, or shortening shoots sooner next year, which gives an advantage in light and resources to the interior shoots. More fertilizer also helps this situation. If nothing is changed, these inner shoots will die within a couple years.

This Pear’s lower branch is losing its leaves early, and it’s a flag of trouble. It’s weaker than the rest. In this situation, consider letting extensions run next year, and / or cutting back the shoots elsewhere harder or sooner. 

Dead shoot on a Pine. Our fault, we might wonder? Maybe not. Older plants will lose twigs now and then, and if only one twig on a tree dies it may not be communicating anything important. If a handful of small twigs that die, maybe look closer for a problem. Multiple shoots dying can indicate a root issue. Also, funguses can cause random shoot loss.

Fall is a time to bring out the notebook and jot down observations: A few new puzzlers perhaps, ending with a question mark. Then problems you’re more familiar with, maybe even confident about, because they were in last year’s notebook. Maybe thoughts on what to try next season. Care misdemeanors are often set to rights by studious notetakers.

Perhaps the most common bonsai truism is that we learn by failure. The notetaker realizes complicity in many oopses, and wishes for better.