When should perennials that bloom in summer and fall be divided?

Dividing perennials that bloom in summer and fall is best done in the spring. This timing allows plants to recover and establish a strong root system before they enter their active growth phase and begin to bloom. Spring typically provides favorable conditions such as milder temperatures and sufficient moisture, which can help reduce stress on the plants during the division process.

Doing this in the spring also ensures that the divided plants have ample time to settle in and develop before the heat of summer arrives, optimizing their chances for healthy growth and blooming later in the season. In contrast, dividing during winter could expose the plants to cold damage, while summer division might stress the plants due to heat and competition for resources. Dividing in the fall could hinder root establishment before winter, risking plant survival as they enter a dormant phase. Thus, spring is the ideal choice for dividing summer and fall blooming perennials.