Thunbergia fragrans clock vine in bloom
image by J.M. Garg: Commons.wikimedia.org
Clock vine, known botanically as Thunbergia, is a tropical, tender-perennial climbing vine that blooms in the summer and fall. Hardy in U.S. Department of Agriculture Zones 8a through 11 and grown as an annual in cooler zones, clock vine is a low-maintenance performer. Depending on the varietal, clock vine flowers come in a wide range of colors from crisp white to blue to yellow to deep persimmon orange. The shape and size of blooms can also vary considerably. Provided with something sturdy to grow upon, water and sunlight, a clock vine will deliver a stunning display of blooms on a background of deep green.
Provide a full-sun to partial-shade exposure for your clock vine. In cooler northern climates, more direct sun will be tolerated. As you move south, with higher heat and/or drier climes, protection from midday or afternoon sun is welcome, and shade will help increase blooming. As peak summer temperatures fade and cooler weather arrives, clock vine will flower more profusely.
Provide a stable support structure on which the clock vine can grow and climb. A sturdy fence, trellis, pergola or arbor will allow the most sunlight penetration and increase the profusion of growth and bloom. Help guide the clock vine tendrils around the support at critical junctures, and the vine's natural climbing habit will do the rest. Flexible garden ties can be used, if needed, but do not tie them too tightly, as this can restrict the healthy growth of the plant.
Water the soil of your clock vine so that it remains evenly moist throughout the growing season. Feed your clock vine twice a month during the growing season with a water-soluble, general-purpose fertilizer or use a slow-release formulation applied once or twice a year, according to the label instructions. When clock vine is planted in containers or hanging baskets, as it often is, daily watering will likely be required in hot and/or dry climates to keep the soil moist.
Allow clock wine to die back in the fall until after the first frost, then cut off the foliage at ground level, or lift the entire plant from the soil and discard. In warmer climes where clock vine grows as a perennial, prune it back in the fall for size, shape and tidiness, if needed, after blooming finishes. If allowed to die back in place, the flowers will self-sow their seed.