Trek adjectives are listed in this post. Each word below can often be found in front of the noun trek in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing TREK.
annual, arduous, country, daily
dangerous, day, difficult, first
great, hour, long, longer
mile, minute, month, overland
short, slow, uphill
Hope this word list had the adjective used with trek you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.