Dipladenia is a perennial vine that also goes by the name "mandevilla." Fast growers, the green leaves of the plant span 10 feet at maturity. This heat-loving plant prefers slightly acidic, well-drained soils and the balmy temperatures of U.S. Department of Agriculture hardiness zones 9 through 11. The large 3- to 5-inch pink, purple, white or red flowers of dipladenia stand out against the bright green foliage, making this plant a real show stopper in the garden. If you are considering planting dipladenia, fall and winter are the best time to do it.
Break up the soil with a pitchfork and test the soil's pH levels. Dipladenia thrives in soil with a pH of 5.5 to 6.5. If the soil pH is lower than 5.5, add lime. If the pH is above 6.5, add peat moss. Follow the label instructions on the lime or peat moss for allocation amounts and application methods.
Space each planting hole at least 18 inches apart. Dig each hole twice the diameter of the root-ball and to a depth equal the root ball's height. Remove the dipladenia from its nursery container and place it in the centre of the hole.
Backfill with native soil and pat the soil around the stem of the dipladenia vine to remove air pockets. Soak the soil immediately with water from a garden hose. Maintain moist soil to a depth of 1 inch for the duration of the first growing season. Daily watering for the first two weeks is essential. After two weeks, twice-a-week watering should suffice. Once established, the dipladenia will require watering only during droughts.
Apply 3 inches of bark chips around the dipladenia plant. Keep the mulch at least 1 inch from the stem to prevent rotting. Mulching serves several purposes; it reduces weeds and improves drainage, and protects roots from damage because of severe or unexpected temperature changes.
Soil testing kits are available at most garden centres, or soil samples can be taken to a county extension office for testing. If dipladenia vines are growing out of control, prune them after blooming has finished. Dipladenia appreciates a dose of 15-0-15 fertiliser several times a year. Check the packaging label on the fertiliser for allocation amounts and frequency.
Avoid over-watering of the dipladenia. Stick your fingers into the soil to feel for moisture. If the soil feels moist at a depth of 1 inch, the vine does not need more water. Too much water can cause the roots of the dipladenia to rot.