Acclimate the trumpet vine by setting the seedling outdoors in a spot protected from direct sunlight and high winds. Leave the vine in its nursery pot during this stage.
Gradually move the vine to a more exposed area in the course of a seven-day period. Bring the vine indoors at night and set it back out in the morning.
Prepare a planting bed at the base of a sturdy trellis, wall or fence in an area with at least six hours of direct sunlight a day. Amend the soil with a 2-inch layer of compost worked into the top 6 to 8 inches of soil before planting.
Dig the planting hole 6 inches from the base of the trellis or wall. Make the hole as deep as the trumpet vine's pot and twice as wide.
Lift the vine from the seedling pot. Set it in the planting hole, so that the trumpet vine is planted at the same depth it was in the pot. Space multiple plants approximately 5 feet apart along the trellis' base.
Fill the hole around the roots with soil and firm the surface with your hands. Water the vines thoroughly after transplanting.