Question

propagation by division
plants that grow in clumps, such as hostas or daylilies, are best propagated by division. this is usually done in early spring or fall when the plant is not flowering. parts that get divided include rhizomes, tubers, runners, and suckers.
propagation by separation
separation takes advantage of plants that produce independent units naturally. bulbs (like tulips) and corms (like gladiolus) can simply be pulled apart to create new \clones\ without any cutting tools.
explain why early spring or fall are the recommended times for performing division on plants.

Explanation:

During early spring or fall, plants are not flowering. Flowering requires energy, so non - flowering periods mean plants have more energy reserved for recovery after division. Also, these seasons typically have milder temperatures and more suitable moisture levels. Milder temperatures reduce stress on the plant from extreme heat or cold, and proper moisture helps the divided plant parts establish roots and regenerate without drying out or being damaged by harsh conditions.

Answer:

Early spring or fall are recommended for plant division because plants are not flowering (saving energy for recovery), and these seasons have milder temperatures and suitable moisture levels to reduce stress and aid in root establishment/regeneration.