Gardenias are named after Alexander Garden a Charleston, SC colonial physician. They are members of the Rubiaceae family. They originated in Japan and China.
Gardenias will grow to between 2′ and 6′ depending on which variety you have and how much sun it receives.
According to UF Extension gardenias can grow in sun, shade or any where in between. I have yet to hear of anyone successfully growing gardenias in the sun down here. They thrive in shade to part shade. They also recommend fertilizing three times a year in Feb, Mar, and Sept. I’m finding one application in Feb. or March works well for me.
I have one gardenia planted in a dry area of my yard, another on the edge of the swale garden. Neither minds the dry or damp conditions so I don’t think they are particular about watering.
Gardenias do fine through the summer heat, they shed leaves if temperatures go below freezing. Both of mine have bounced back from last winter’s freezes.
Yellowing leaves may occur because of nutrient deficiencies related to our very basic ph soil. UF Extension recommends acidifying the soil. I purchased some iron granules for lawns and scattered them through all the gardens this spring. You likely want to add some iron and then fertilize regularly. Gardenias are heavy feeders.
As with all flowering shrubs, prune after the plant is done flowering. Pruning done after October will reduce spring flowering.
Most cases of Gardenia suicide can be attributed to nematodes, a soil born root eater. Gardenias are highly susceptible to nematodes. There is nothing you can do. The plant is either grown on resistant root stock or not. Wilting and rapid death will follow if the plant is attacked by nematodes. Gardenias need to be grown on South African Gardenia thunbergia root stock to be protected.
When planting your gardenia add some peat moss to soil and around the area, gardenias prefer more acid soil than is usually found around here.
I find gardenias either die quickly after planting or settle in and do well with little care. If one dies, try again.
Watch for spider mites, white flies, and scale. All can be treated by washing off or spraying with orange oil.
Sooty mold usually caused by aphids, just wash it off with soapy water.
Some of these survived the drought and heat of summer 2011 some didn’t. The one in a normally boggy area did the best.