This is just an observation and it could be completely coincidental. I planted a ring of garlic around 2 apple tree's and 2 cherry tree's last year. They receive about the same amount of sun and water. This year as it is getting closer to harvest time I'm noticing that the garlic around the apple tree's is noticeably larger. The garlic around the cherries look kinda small and spindly while the garlic around the apples looks thick and tall. Could it be that garlic doesn't get along with cherry tree's? I also have asian pear tree's now that I can try this with this fall.
if the tree's are relatively the same size and age that maybe the cherry tree needs more water or the same nutrients as the garlic and thus they grow smaller...hard to say for sure. Great observations and further study us needed...keep us posted