Photos : February 2000, at Petchabun, Thailand (Nikon FM2n 105mm F.2.5)

Here is article about the un-pronounceable name from Curtis Clark

Why does the genus have such a strange name?

Eschscholtz was of German parentage, but his parents had settled in Russia. 
His family name had originally been spelled "Escholtz" in Germany, but when the name was transliterated to the Cyrillic alphabet used then and now for Russian, it appeared as (e-sh-sh-o-l-ts). 

Upon conversion back to German the name became "Eschscholtz" with the doubled "sch". 
Chamisso latinized the name as "Eschscholzius", without the "t". 

This is not unexpected; "Eschscholtz" and "Eschscholz" would have been (and still are) pronounced the same in German, and at that time spelling was not firmly fixed in most European languages. 

In his description of the new genus in 1820, Chamisso called it Eschscholzia, which is the correct name according to the provisions of the International Code of Botanical Nomenclature. 
However, in the plate accompanying the description, he labeled it Eschholzia, and elsewhere in the publication, Eschscholtzia. 
This latter misspelling was widely used for over a century and is still occasionally seen today.

Curtis Clark
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