So usually, adjectives are kind of a last go-to for poets. Adjectives and adverbs are almost always pegged as weaker parts of speech than nouns and verbs, because they don't actually refer to anything in and of themselves – they just modify other stuff. So they're considered "secondary" parts of speech, in a lot of ways.
Not with this poem.
A lot of the force in "Big Poppy" actually rests on the piling up of adjectives. Some of the most intense lines are just layers upon layers of modifiers. We can demonstrate! Let's play a fun game, called Find the Examples of Adjective Piling:
Pile Example 1: "royal [adj!] carpet of a down-hung [adj!], / Shrivel-edged [adj!], unhinged [adj!] petal, her first [adj!]-about-to-fall" (6-7)
Pile Example 2: "Her carnival paper [compound adj!] skirts, luminous [adj!] near-orange [adj!] / Embrace him helplessly [adv!]" (10-11)
Pile Example 3: "her big [adj!], lewd [adj!], bold [adj!] eye, in its sooty [adj!] lashes" (24)
We could go on, but you see what we mean, right? All those adjectives just fall over each other, creating a kind of freight train of momentum that's extremely hard to do with secondary parts of speech. But Hughes has had a lot of practice. We think it shows.