Spring
If you prune Flowering Quince to shape in the spring after flowering, you will stimulate growth of flowering spurs which will improve bloom for next year. At the same time however pruning now will reduce fruit production for the current year if that important to you. For more information see the files on Pruning Shade and Flowering Trees and Choosing Pruning Tools

Summer
Because this plant is quite drought tolerant, it should not need to be watered very often.

Fall
October is usually the best time to make quince jams, jellies, or marmalades.

Winter
Flower buds are susceptible to significant damage from early spring frosts. You can protect the plant somewhat by covering it with fleece or floating row cover if late frosts are expected.