Oranges and gardenias share a predilection for warm subtropical to temperate climates and rich, acidic soil. Orange trees, however, prefer full sun while gardenias benefit from filtered sun or afternoon shade cover in most regions. Both needs can be met provided that orange trees are large enough or planted en masse to provide light for the gardenias below. This pairing can be accomplished in ground plantings as well as in containers. Planted together you will have the sweet scent of orange blossoms followed by the spicy gardenia flowers, and then the orange fruits offset by the deep glossy green of the gardenia foliage. Executed carefully this can be an outstanding pairing.
Create a container planting of a dwarf orange tree and dwarf gardenias for a patio, orangery or sun room by selecting a planter roughly twice to three times the size of the orange tree root mass and with ample drainage holes. Fill the container with potting soil and amend with several pounds of compost and aged manure to boost the quality of the soil. If soil has clay, add sharp sand for drainage. Plant the orange tree in the center and surround with three to five dwarf gardenia plants at the perimeter of the planter.
Plant the pairing in the ground by tilling up and amending the soil as needed. Place the orange tree or trees in position, first keeping the top of the root ball level with the surrounding soil. Fill in with gardenia cultivars of choice to create a carpet of gardenia shrubs under the oranges. Keep the shrubs outside of the main root ball zone of the orange as the gardenia branches will grow to fill in the area without disturbing the root ball of the orange.
Water the joint planting area deeply once a week to every 10 days to keep the soil evenly moist but not wet. Fertilize, according to the product label dosing guidance, with a complete formula containing nitrogen, phosphorus and potassium designed for acid-loving plants such as Miracid, Citrus-tone or Holly-tone.