|I would like to continue to grow these tropicals inside during our winter months. I have a large south facing window. Would this be possible, and if so do you have any helpful hints?|
|The mandevilla can be brought inside and will sometimes continue to bloom, but in my experience it will probably defoliate and sulk all winter even in a very bright window -- just because we have such short winter days. To try to keep it blooming, bring it indoors before temperatures dip below the mid fifties. If it defoliates, cut back on the watering somewhat and do not fertilize it. You can keep it a bit cooler at that point, say between 50 and 65 degrees. Trim it back and then in spring when it does start to grow again go ahead and begin to fertilize and water a bit more again. When the weather warms up take it back outside again.
The gardenia can be really difficult. My biggest hint would be to try to keep it in a relativedly cool room temperature with good air circulation and good humidity. Here are general care instructions for it.
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 them both!