Cosmos – From Here.
Very little maintenance is required. Tall cosmos varieties can flop over, so if you are not growing them closely or near other plants that can support them, you may need some type of staking. The only real maintenance cosmos plants need is deadheading which will prolong the flowering season. If you fall behind, simply shear the plants by about 1/3, when most of the flowers have faded. You’ll get a second flush of leaves and flowers.