Royal Poinciana, known botanically as Delonix regia, is a tropical flowering and fruiting tree known for its lush bright red to coral orange flowers in the late spring and early summer. The tree is prized for its large, spreading canopy that is an ideal shade tree in the warmer climates of USDA zones 10 and 11 where the tree lives. Younger Royal Poinciana trees are fertilized more heavily than older trees. As this species is often grown over or adjacent to a lawn, Royal Poinciana trees often get enough fertilizer from what is applied to the lawn grass, requiring no supplementation.
Select a slow-release or organic complete fertilizer with a guaranteed analysis of 15-5-15 or 16-4-8, or one with a similar ratio of macro-nutrients.
Feed new trees under 3 years of age two to three times a year. Feed trees 3 years and older two times a year unless growing near a lawn that is fertilized regularly. Established trees older than 5 years of age rarely require fertilization unless growing in nutrient-poor soil. Make the first feeding in spring, the second in early fall. The third optional feeding should be made in midsummer.
Apply the fertilizer according to the product label dosing directions but do not exceed a rate of 1 lb. of actual nitrogen for every 1,000 square feet of soil area around the tree.
Cast the fertilizer, with a gloved hand, over the root zone of the tree starting a foot out from the trunk and extending past the drip line to 1 1/2 to two times the diameter of the tree canopy.
Water in the fertilizer well until the soil is drenched to a depth of 6 inches to speed the nutrients into the root zone.