Ask a Question forum: What's wrong with my Dipladenia?

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Name: Beth Smith
Plainfield, IL
Beth19
Jun 21, 2014 1:23 PM CST
I live on Illinois and bought three Dipladenia plants at Menards. When I first got them they were very pretty and full. Now, leaves and becoming yellow and falling off and the flowers have white-ish spots on them. There are also far fewer flowers. What am I doing wrong? I know these are tropical plants, but it is the summer and they get plenty of sunlight. Am I overwatering? Is it insects? I'd really like help, as I think these plants are so pretty. I've attached a picture below. Thanks!

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Name: Elaine
South Sarasota, Florida (Zone 9b)
The one constant in life is change
Cat Lover Master Gardener: Florida Tropicals Multi-Region Gardener Vegetable Grower Region: Florida
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dyzzypyxxy
Jun 21, 2014 2:00 PM CST
Welcome Beth. Hope we can help.

Have you checked the backs of the leaves for insects? Might want to use a magnifying glass for spider mites. Soapy water is the solution for those,1/2 tsp. Per quart of water.
Spray a couple of times per week for a while, and be sure to hit under sides of the leaves.

Could you post a pic of the whole plant or plants? They are fairly vigorous and might need repotting. Also just turning the plant out of the pot can give you a good indication of over watering.
Elaine

"Success is stumbling from failure to failure with no loss of enthusiasm." –Winston Churchill
[Last edited by dyzzypyxxy - Jun 21, 2014 2:34 PM (+)]
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Name: Lin
Florida (Zone 9b)
Region: United States of America Morning Glories Region: Florida Houseplants Charter ATP Member I was one of the first 300 contributors to the plant database!
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plantladylin
Jun 21, 2014 2:50 PM CST
Hi Beth,

Welcome! from me too!

The white coloration on the blooms in your photo looks like water spots which can be alleviated by watering from the bottom. Yellowing leaves can be from overwatering and I'm wondering if the soil they are planted in perhaps is holding too much moisture. Some nurseries plant in very heavy soil that does not drain well, I assume to keep the plants moist while sitting on shelves in the garden centers waiting for consumers to buy them. Smiling Mandevilla/Dipladenia need a well draining potting medium. I also wonder if they could be root-bound, possibly in need of larger containers. I find Mandevilla also does best with some shade; bright indirect light but no direct sunlight, which will burn the foliage. For more blooms, fertilizer with higher phosphorus (high middle number) will help produce more blooms but only use half strength to what is listed on the package.

Good luck with your plants and I hope they do well for you. Even though they are tropical plants you can overwinter them by moving them indoors when temperatures dip below @ 50ºF. There are several Mandevilla (Dipladenia) listed in our database with information and photos: http://garden.org/plants/search/text.php?q=Dipladenia&button...
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Name: Elaine
South Sarasota, Florida (Zone 9b)
The one constant in life is change
Cat Lover Master Gardener: Florida Tropicals Multi-Region Gardener Vegetable Grower Region: Florida
Herbs Orchids Birds Garden Ideas: Level 2 Garden Sages Celebrating Gardening: 2015
Image
dyzzypyxxy
Jun 21, 2014 4:29 PM CST
Couple more thoughts. Have you had cool nights, under 55deg or so?

Also how have you been fertilizing?
Elaine

"Success is stumbling from failure to failure with no loss of enthusiasm." –Winston Churchill

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