Dahlia care:

Planted in the ground or in a large pot within the next week.

Water every couple days or when they feel dry.

When the tall/leggy red flowers have bloomed, cut them close to the leaves to encourage more leaves and blossoms.

Deadhead blooms regularly throughout the summer.

If there is a frost cover them overnight. In the winter, you can dig up and store in the garage and plant again next spring.