Vinca is the tropical flowering plant that can grow in wide range of soils. Even if you forget to apply fertilizers, they bloom heavily from spring to the end of summer. 

If you grow one single hollyhock plant, then they will spread naturally in your garden. They can also grow in wide range of soils with minimal care. 

Popular for white, red to pink coloured flowers can grow easily in well draining soil, rich in organic matter. They are hardly affected by any pests or diseases. 

They goes under dormancy in cold winters, and start growing & flowering from spring to the end of summers. Once established, they grow easily. 

One of the most common flowering and easy to care plant of tropical region is hibiscus. However, you must learn to control mealy bugs, a major pest of hibiscus.