Our climate zone here in Mono is 4B at best. It faces south with sun all day. The conditions are dry and we do have sandy soil.
Thank you for your inquiry regarding getting your trumpet vine to bloom.
While there are several cultivars of trumpet vine, I will assume you have the basic trumpet vine (Campsis radicans). It is the hardiest form and should survive in zone 4B or 5. It is a fast-growing vine that will exceed 30 feet unless prune regularly.
This vine is easily grown in a wide variety of soils. It thrives best in lean to average soils with regular moisture in full sun to part shade. Foliage grows well in shade.
These plants need good sun for best flowering. Pruning is recommended to increase flower bloom and also to control the size.
Trumpet vines bloom in midsummer on the current year’s growth. So, the best time to prune is after all the flowers have dropped for the season. Trimming the branches in the autumn also prevents seedpods from dropping and starting new vines.
To prune, begin by removing old stems that have become spindly or weak.
Cut the top stems down to encourage new, fuller growth. Make sure to leave at least 3-4 buds per stem and only remove about 1/3 of the wood at a time, to avoid shocking the vine.