Almost always appears in compounds: 和蔼 (kindly), 蔼然 (gently), 和蔼可亲 (warm and approachable). The grass radical 艹 is a hint at the original 'lush vegetation' sense, which extended into 'a kindly, gentle aura.'
艹 is the top-position form of 草. Here it carries the literary lush-vegetation sense of 蔼 directly, while the everyday meaning (kindly, amiable) leans on the soft, gentle imagery of dense leafy growth, the metaphor of warmth and abundance.
谒 provides the sound, drifted from yè to ǎi via the shared 曷 phonetic core (also seen in 喝, 渴). The polite-greeting connotation of 谒 (formal calls) layers nicely under 蔼's modern friendly-speech sense.
