|Several years ago I purchased a garden plant for my wife. Through the years it has grown. In the Spring I place it outside. Last year it blossomed and bloomed beautifully. This year it has lost all it's leaves and they are|
|Gardenias are finicky and just about any change can make them defoliate. For the repotting, without knowing what kind of soil you used it's hard to say whether there is excess fertilizer or if the pH is correct, or not.
Hollytone is very slow release so I would not expect it to "burn" a plant. However, you never want to overfertilize as this can cause a build up of salts in the soil. Excess salts can cause foliage problems, too. If you exceeded the label rate on the fertilizer, or if you have fertilized heavily over the years, you may see a build-up. This is usually leached out to some extent when the plant is outside for the summer and is rained on. You can also leach the soil by several heavy waterings in quick succession, being sure to allow the excess to run out freely.
You might want to test the pH and see -- ideally it would be about 5 to 5.5, but you would not want ot make an abrupt change from what is was initially. You might want to try to test the original soil closer to the stem as well as the new mix you used.
Also, make sure it is draining well as overwatering can cause drying just as under watering can.
Sometimes repotting causes issues if the roots do not grow into the new soil; you might have a case where the original soil is drying out but the new soil is still wet. Or, you might be inadvertently overwatering especially if the new container is substantially larger than the old. Too, if the old soil and new soil are not similar in texture, you could have drainage issues.
I hope this helps you trouble shoot. You might also want to take a look at the following general gardenia tips and see if anything might apply.
Unfortunately, the gardenia is often a disappointment to gardeners because it can be very, very demanding. In some cases it is better to consider it as a florist bouquet and dispose of it once the flowers have faded. However, you might be able to keep it going as a container plant. Here are some general care notes and instructions.
Gardenias are finicky, and any change of location or humidity or sun can set them back, so do not be too surprised if it suffers some initial shock from being moved.
In general, bright light is essential, but avoid direct mid-day sun in the summer. It may summer outside when temperatures are settled, place it in a bright location out of direct sun, in dappled light all day or in gentle morning sun. Buds that turn black and drop, and bottom leaves that are yellowed are sure signs that gardenias aren't getting enough light.
For flower buds to form and thrive, night temperatures need to be between 60-65F. During the day, temperatures should be 70-75F. A very constant, even temperature within these ranges is required or buds will drop. Also avoid drafts or moving the plant. Simply moving the plant often causes bud drop, as may any imbalance in the growing conditions.
Keep the soil evenly moist (but not sopping wet)at all times except in winter when watering should be reduced slightly to compensate for the seasonally slower growth.
Fertilize regularly but lightly during active growth periods (spring and summer) with a water soluble fertilizer for acid loving plants according to the label instructions. Check the label also to make sure it includes micronutrients or "minors" to assure a broad based supply of minerals.
Gardenias are very susceptible to spider mites, which can distort the buds and cause leaves to yellow and drop. Look on the undersides of the leaves for tiny black specks and whitish webbing. If necessary, use an insecticidal soap spray according to the label instructions to control these, be sure to repeat to control subsequent generations and treat all surfaces of the plant. Washing the plant with a spray of tepid water can also help rinse them away.
Routine misting with water helps raise the humidity and consequently discourages spider mites but it is better to set it on a humidity tray of pebbles and water or use a humidifier especially during the winter heating season when indoor air is very dry.
Finally, yellow leaves can be a natural occurance since the old leaves normally turn yellow and fall off, or could indicate inadequate light, or can signal insufficient water or even the use of hard water. Leaf drop can also be caused by improper soil pH (gardenias require 5 to 5.5 pH - on the acid side) or a nutrient deficiciency.
As you can see, these are not easy plants. Occasionally we get lucky and a gardenia will thrive. If not, don't take it personally, they are very difficult. Good luck with your plant!