Sub-tropical flowering trees are defined as those growing well between 23.5° (Tropic of Cancer) and about 38° north latitude (southern Virginia); this coincides with USDA hardiness zones 7 – 11. Most of Florida and westward along the Gulf Coast are in zones 9 or higher. In zones 7 and 8 in particular, average and extreme temperature conditions are influenced locally by three key site factors which are important to tree growth. 1) Elevation above sea level, because annual land temperatures decrease with elevation; 2) Proximity to a water body, because seaside or lakeside areas are typically warmer than inland locations; 3) Orientation of tree planting, because the north facing side of a structure or landform will almost always be cooler than the more protected south facing side, especially when the occasional Blue Norther storm occurs. This factor is particularly important in locations at or near the limit of the subtropical zone. Subtropical tree performance may vary where occasional frost occurs; in addition, the growth rate may be slower, foliage not as impressive, and flowering and fruiting reduced or suppressed. Examples of subtropical trees, exotic and native, for marginal subtropical areas include acacias such as delicate-leaved Poponax (Acacia tortuosa); the small evergreen Pineapple Guava (Acca sellowiana); the fall color of the Red Maple (Acer rubrum); the beautiful flowers of the Floss Silk Tree (Chorisia speciosa); species of Cordia such as the handsome White Geiger (Cordia boissieri), distinctive hollies like East Palatka (Ilex x attenuata), the attractive crape myrtles (Lagerstroemia spp.); the spreading Japanese Ligustrum (Ligustrum japonicum); the large Bull Bay (Magnolia grandiflora); the handsome evergreen Live Oak (Quercus virginiana) and the shrublike Silver Saw Palmetto (Serenoa repens). These plants, and certain others, present options for foliage and flowering trees to enhance any garden. Gardeners uncertain of their local climatic conditions may consult the USDA Plant Hardiness Zone Map (http://planthardiness.ars.usda.gov/PHZMWeb/) which provides interactive information by Zip Code.
Treeworld has a wide choice of subtropical trees, including those mentioned above, from which to select the best plants for landscaping any residential, commercial or public location.