The Vietnam gardenia — Gardenia augusta “Vietnam” — is a plant for skilled gardeners who like a challenge. This gardenia from Southeast Asia likes acid conditions. Growing it in our alkaline soils means keeping on top of its nutrition, but the beautiful, solitary flowers, with lustrous white petals forming pinwheel-like corollas, should make the effort worthwhile.
The shrub, in the coffee family, has somewhat quilted leaves. Several of the small shrubs planted together make a nice bed. The Tropical Flowering Tree Society says this is a cold hardy plant that blooms almost constantly.
This gardenia grow to 4 to 6 feet. It prefers full sun to light shade. Gardenias like rich soil and even moisture. Your instructions, therefore, are to amend with organic material such as compost or composted cow manure, apply three or four inches of mulch, and use a fertilizer for acid-loving plants such as ixora and gardenia.
When yellowing in the leaves becomes apparent (more likely in Miami-Dade than in Broward County), use a chelated iron drench. Chelated iron keeps the iron available to be absorbed by plant roots. Gardenias also are susceptible to nematodes. Mulch and a good nutritional program can help the plant grow anyway; grafting on G. thunbergia rootstock, which is resistant to nematodes, is best.
— MIAMI HERALD ARCHIVES