I have two types of flowers that were blooming at the beginning of the year but have stopped. Everything else that I am growing looks great but not the purple Lilac and Peony flowers. They both grow at the side of the yard with FULL sun. There is some mulch at the base of the plants. Is the damage on these leaves from an insect or fungus? What should I do to help them bloom again?
Lilacs and peonies are perennial plants that bloom only for a short period of time in the spring. Once they bloom and the flowers die, they are finished flowering for the season. They will not bloom again until next spring. This is a normal part of their biology and there is nothing you can do but wait until next year.
Peonies very commonly get two fungal diseases: Cladosporium leaf spot and botrytis. Sanitation is an important step in managing these fungal diseases. Cut off and remove all plant debris each fall (in October). Put the debris in the trash (do not compost it).
Similarly, lilacs are susceptible to several fungal diseases, most commonly powdery mildew. No treatment would be effective once symptoms are already present.
Placing mulch around the base of your plants is good, but make sure it is not too deep (no more than 2-3") and keep the mulch a few inches away from the base of the plant. Mulch should not be placed right up against the stems.