Mandevilla vines, also still called Dipladenia, are native to the woodlands of tropical Central and South America. Although there are 125 species of this vine, only three or four species (and their complex hybrid crosses) are grown in gardens or in patio containers. Mandevilla vines are admired for their dark green leaves and large, trumpet-shaped flowers. Mandevilla vines do not tolerate subfreezing temperatures and survive outdoors only in USDA Plant Hardiness Zones 9 and warmer.
Mandevilla vines usually create twining woody stems between 10 and 15 feet long. In tropical climates, old plants can have stems that climb as high as 20 to 30 feet on tree or palm trunks. If there is nothing for the stems to grasp onto and grow vertically, the vines will sprawl and climb over fences or other shrubs in a haphazard manner.
A key feature to quickly determining if a tropical vine is a mandevilla is to snap a leaf or break a stem. Mandevilla vines, along with other members of the dogbane family (Apocynaceae), exude a milky white sap from veins. This sap contains toxins and should not be eaten or allowed to get into you eyes.
Beside the twining tendril tips of the green stem tips, a close look at the foliage can provide clues to the mandevilla vine's identity. The dark green leaves are oval and tapering, with a point at their ends. Some species or hybrids have very glossy leaves, while others are more matte in luster or display corrugated veins on the leaf blades. Foliage also may be smooth or slightly fuzzy. The leaves are always held in opposite pairs on the stems.
Most mandevillas bloom when temperatures are warm. In temperate zones where the mandevilla is a potted plant, it will usually flower non-stop across the summer. In tropical regions, flowering is most apparent in spring, wanes or ceases in the most intense heat and humidity of midsummer, and resumes in the tropical autumn. Only if temperatures remain warm and water abundant will mandevilla vines shyly produce flowers in the winter. The individual flowers are trumpet-like and held horizontally from the vine stems. The five-petal lobes spiral open from the bud and reveal a cup-like throat that often is yellow or darker red. The petals can be white, pink or red or any shade in between.
The vine known as yellow mandevilla (Pentalinon luteum) is similar to the plants that belong to the genus Mandevilla. The yellow mandevilla, also called sundial or wild allamanda, has yellow-green leaves and light lemon yellow flowers that are smaller in size that more true mandevilla vines. Yellow mandevilla also reveals a milky sap from its stems and leaves when broken since it also is a member of the dogbane family. This species tends to be found in much hotter growing conditions and in nutrient-poor, sandy soils that are moist in summer and quite dry the rest of the year, according to Kirsten Albrecht Llamas, author of "Tropical Flowering Plants."