I am a plant known for my vibrant, showy flowers, often used in leis. I thrive in tropical climates and come in a wide array of colors. My petals have a distinctive trumpet shape, and I am often associated with the phrase 'aloha'. What am I?

1. My flowers are popular in Hawaiian culture.
2. I am a shrub or small tree.
3. I prefer full sun and well-drained soil.
4. My flowers can attract hummingbirds.