Native from Texas southward all the way to Argentina, yellowbells (Tecoma stans) is also known by the common names "esperanza" and "yellow elder." Prolific in producing loose clusters of canary yellow, bell-like flowers from spring to early winter, yellowbells can grow as an irregular small tree (10 to 30 feet tall) in frost-free areas or as a rejuvenating perennial-like shrub where winters have mild subfreezing temperatures. Grow yellowbells in a mixed flower or shrub border in USDA hardiness zones 8 and warmer.
For the fullest branching and abundantly flowering plants, plant yellowbells in full sun exposures. It is tolerant of partially sunny locations, but it should never receive less than six to eight hours of direct sun rays daily. Insufficient light causes plants to become exceptionally leggy or to lean toward the light. Flowering may also be diminished.
Choose a well-draining soil in your garden for the yellowbells. Tolerant of drought, lushest growth occurs in sandy soils amended with lots of organic matter to improve fertility and moisture retention. Avoid heavy clay soils, dry nutrient-poor sand and those that remain soggy after rains or irrigation. A non-alkaline soil ensures the feathery foliage retains its dark glossy green color.
From spring to mid-autumn, water the plant freely, because this will promote lush growth and repeated flushes of new flowering clusters on new branch tips. Reduce watering in the winter months when temperatures naturally cool, sunlight intensity is soft and flowering and new growth ends. Keep soil slightly dry. In severe droughts some foliage may abort, but once established in the landscape, yellowbells tolerate dry soil and heat and both arid or humid air well.
Alongside the watering regimen, fertilize the yellowbells in the spring to mid-autumn months only; never in winter. Add fresh compost or well-rotten manure as a mulch or soil top-dressing any time of year to improve the soil's fertility. Granular, slow-release fertilizer can be sprinkled on the root zone in spring and summer according to product label directions. Occasional waterings with a well-balanced water soluble fertilizer can also be done from late spring to the end of summer. Liquid fertilizers are not as effective in sandy soils, since they quickly leach.
To improve the growth habit of the yellowbells plant, consider pruning back the plant in very late winter to an uniform, nicely-branching skeleton structure. New growth will sprout back quickly in spring with warmth and moist soil. Also consider removing the clusters of seed pods that form after the flowers drop away. Tip pruning the branches to remove the seed pods results in new flowers.