At a truly tropical frost-free climate, constant temperatures and even day lengths promote year old flowering in plants. In regions with changing temperatures, including occasional icy weather, some shrubs will keep flowering except for those cold snaps, when flowering ceases for a short time. To encourage continuous thriving, select a bush that’s capable of year round blossom and provide it the most favorable microclimate you’ve got or keep it as a container plant and then bring it indoors for the winter.
One of the most reliable non-stop blooming shrubs for U.S. Department of Agriculture plant hardiness zones 9 through 11 is trailing lantana (Lantana montevidensis, formerly L. sellowiana). Bushes grow 8 to 12 inches tall and 3 to 6 feet wide, with 1-inch-wide clusters of small purple flowers at branch ends. It can cascade over a rock wall, serve as a ground cover or grow in a container or hanging basket. Flowers attract butterflies and mammals, and leaves turn purplish in winter. “Lavender Swirl” (L. montevidensis “Lavender Swirl”) contains both white and lavender flowers on precisely the same bush.
A tough freely-flowering plant which tolerates most growing states, Mexican petunia (Ruellia brittoniana) can also be called Mexican bluebell. Plants grow 3 to 4 feet high and two to three feet wide. Purple tubular flowers attract butterflies and hummingbirds. Hardy in USDA zones 8 through 11, Mexican petunia grows as an annual in colder zones. In frost-free areas, it flowers continuously. Cultivars include “Purple Showers,” “Katie,” “Bonita Pink” and “Chi Chi,” that has pink blossoms.
A native Mediterranean plant, oleander now grows world-wide in warm-winter places. Shrubs tolerate heat and drought and require care aside from pruning once established. They grow in USDA zones 8 through 11. Standard varieties grow 6 to 12 feet tall, but smaller-growing cultivars include “Petite Pink” and “Petite Salmon” which grow to 3 or 4 feet tall, and red-flowered “Algiers,” growing 5 to 8 feet tall. Oleanders blossom always through warm months of the year and into winter in frost-free places. They are generally kept as container plants in colder European countries and overwintered indoors.
Grown primarily for the extreme fragrance of the white bell-shaped blossoms, evergreen orange jessamine (Murraya paniculata) flowers off and on all year in USDA zones 9 through 11. Bushes grow 6 feet tall and 4 feet wide, and also make great hedges, privacy screens and foundation plantings. Find plants in patios or near windows to allow the fragrance to waft into living spaces. Native to Malaysia, plants need regular watering.