Many people think of poinsettias as indoor potted plants for the Christmas season, which is true in much of the country. Thankfully, those of us in Miami can enjoy perennial foliage and late fall color by planting our poinsettias outdoors.
These plants are tropical, so they can't really tolerate frost. In our outdoor beds we must select an area that drains well, provides rich soil and supplies the plants with the full sun they need. Poinsettias can reach several feet tall when grown outdoors, so make sure you give them plenty of room to spread upward and outward!
During the summer poinsettias need regular watering. Just keep the soil moist and mulch well around the plants, and they'll be fine. You rarely need to water during the rainy season, but still check the soil occasionally to make sure it doesn't dry. Fertilize with a balanced feed once monthly in the spring and summer to ensure the plants get the nutrients they need.
The most difficult part of poinsettia culture is getting them to develop their colorful red bracts in the fall and winter. Poinsettias need 12 hours of absolute darkness to develop color. Even the light from a street lamp can provide too much nighttime light. The most sure-fire way to get red poinsettias is to cover them with a black trash bag at night, but remove it during the day. Within a couple of months you'll be rewarded with deep red flower bracts – just in time for the winter holidays.