gardenia white spots - Knowledgebase Question

Marblehead, MA
Avatar for gdhionis
Question by gdhionis
December 26, 2005
I purchased two gardenia plants from Monrovia in Marblehead this summer. I had them outside and they thrived and bloomed. However since bringing them inside, I have them by a door which provides southerly sun exposure, they have white spots all over them. The leaves look ok but I am concerned. What should I do for them?

Answer from NGA
December 26, 2005
Based on your description I am not certain what is happening. Sometimes exposure to intense direct sun (as they may be receiving in a southern window if sun is reflecting off of snow, for example) can cause a discoloration although I would not really expect this in mid winter with its cloudy days. You might try a location that is bright but without too much direct sun. Sometimes spider mites will cause discoloration, but this is usually a stippling pattern in yellow rather than white. You would also see fine webbing on the undersides of the leaves. If you find these, try spraying with insecticidal soap. Next, although not common on this plant, you might be seeing powdery mildew, it is powdery white film on the leaves. This can be rinsed off with tepid water, then provide better air circulation for the plants. If none of these seem probable, I would suggest you check with your local professional nursery staff and see if they can help with a diagnosis. In the meantime, here is some general care information for your plants since this is your first winter with them indoors. Good luck!

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 plants!

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