Dahlia ‘Sincerity’ likes a lot of sun, so make sure you put the plant in a spot where it gets at least 6 hours of sun a day. Be sure to water the plants regularly, especially during dry periods. It is good to fertilize the plants occasionally with a fertilizer. Dahlias can grow tall, so it is advisable to support them with canes or a plant rack to keep them straight. Wilted flowers can be removed regularly to encourage flowering. If you want to use the flowers as cut flowers, it is best to cut the stems in the morning, before the flowers are fully open. In cold climates, it is important to dig up the root tubers in the fall and store them in a cool, dry place for the winter.

General care tips can be found here