Final answer:
The sentence provided is a simple sentence, as it contains only one independent clause and has no dependent clauses.
Step-by-step explanation:
The sentence in question, "Daylilies—hardy perennial plants of the lily family—are popular for home gardens due to their low-maintenance nature and their tolerance of both drought and frost," is a simple sentence. This is because it contains one independent clause and no dependent clauses. The hyphens are used here to include an explanatory note, but it does not change the classification of the sentence.