How to Prune evening trumpet flower?
On established plants, shorten sideshoots to three or four buds from the permanent framework; remove crowded or damaged shoots. Prune after flowering has finished.

evening trumpet flower · Gelsemium sempervirens
Also known as: Carolina jasmine; Carolina yellow jasmine; false jasmine; yellow jessamine
Grow under glass in a loam based potting compost in full or bright filtered light with shade from hot sun. Water freely when in growth applying a balanced liquid fertiliser monthly. Water sparingly in winter. Can be grown outdoors in milder areas in most moderately fertile soils but will require protection from cold drying winds
On established plants, shorten sideshoots to three or four buds from the permanent framework; remove crowded or damaged shoots. Prune after flowering has finished.