What is the reason why toothpicks piled downhill lose one a year?

One-year-old toothpicks piled downhill may have been sprayed with herbicides before digging.

Lagerstroemia indica has been sprayed with herbicides like this, and the clustered fine buds are not long enough. It is estimated that it will take two years to recover. Normal buds are so dense only when they are cut at the top, and the buds on the trunk are sparse, with two or three buds at most.

Downhill pile is a bonsai pile blank excavated from wild forest, whose roots are severely cut off, that is, a stump taken from the mountain. Because many bonsai materials are in deep forests or wild valleys, it is customary to call non-artificially cultivated piles downhill piles.