Crapemyrtle – White Crystals on Tips

Q: I noticed today that almost all the leaves on my crape myrtles (Natchez) have tiny (pencil point) white deposits on the tips of the leaves.

Under a magnifying glass the deposits
look like perlite, and are crunchy. They definitely are not insects.

What could this be? Is it due to lack of

A: The tip deposits are minerals left behind when plant fluids evaporated.

The fluids came to the tip through a process called guttation, whereby a plant leaks fluid through pores called hydathodes.

Guttation takes place under conditions of high relative humidity and low transpiration (moisture release through leaf stomates).

Guttation fluid contains potassium (between 18 and 30 mg/l) and sugar (around 40 mg/l).

I tasted the crystals myself and found them to be salty/sweet, as expected.

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