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, but I’m going to try some this summer. 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. The one in the dry area died. Clearly they prefer damp areas.
Gardenias do fine through the summer heat, they shed leaves if temperatures go below freezing. Mine regularly bounce back from winter 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. Fertilize them often. Yellowing leaves mean they want more nutrients.
As with all flowering shrubs, prune after the plant is done flowering. Pruning done after October will reduce spring flowering.
I find gardenias either die quickly after planting or settle in and do well with little care. If one dies, try again.
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.
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.
These are very easy to propagate from cuttings. Take a ~6″ cutting. Remove the lower leaves, you want 3 or more leaf nodes under the soil. I use sphagnum moss for propagating plants. Cover to keep the humidity up. Plant outside in spring or fall.
These can be tricky to grow as house plants. They like to be cool at night and in a sunny place in the day. So put them near a sunny, drafty window. It you don’t have a drafty window stick them near your door. I have them outdoors now that we have moved south and they can stand a few nights below freezing comfortably, so don’t worry about them getting cold. In the summer put them outside after last frost, in a semi-shaded area, and bring them in before first frost. If it is too cold for them they will drop their buds and leaves may be light green. So cooler but not cold.
They like water, and need water almost daily when grown indoors. Keep a close eye on them and make sure the soil stays moist. They will drop all their leaves at a moments notice if the soil gets dry. Luckily they will rebound and grow new leaves if you correct the situation quickly. One of the things that makes a gardenia worth the trouble is that it is a winter flowering plant, at least indoors, setting blossoms when the nights are cool. They are heavily scented and one flower will fill the house with perfume.
Gardenias need acidic soil, basic water will yellow their leaves. So when you water them add a tablespoon of apple cider or plain white vinegar to a gallon of water.
Bud drop is usually from uneven watering or warm dry house air. Keeping them near a drafty window or door helps.
I found them to be very prone to spider mites when grown inside. This can usually be cured by washing the plant with water and liquid dish soap.