My Mexican petunias have slowly developed white stems. There are about eight different plants in the same area and the first one that turned white has died. What could be causing this? Thank you.
It sounds like it is a fungus, but it will be hard to confirm without a picture. Can you please send us a picture of the plant? If it is a fungus, a fungicide will help correct it.
There is a soil borne fungus that actually consumes organic matter in the soil. Occasionally, it progresses to the extent it affects your desirable plants. As a home owner, your best bet would be to drench the soil with a mix of water and hydrogen peroxide. Include a few drops of soap as the fungus repels water which makes control in the soil difficult.
I have lots of purple and pink Mexican Petunias. How do I grow a white one?
Do a search for 'Icicles' variety of Wild Petunia.
https://www.gardeningknowhow.com/ornamental/flowers/ruellia/growing-ruellia-wild-petunias.htm
Our recent cold temps have made our many Mexican petunia plants kaput. Do we remove the blackened foliage or leave it for spring?
If the whole plant has been killed back to the ground, you can cut off all the foliage. The plant should grow back from the roots in the spring. If just the tips of leaves have been damaged by the cold, it's best to leave the plants standing until spring.
Hello: My petunia will not open. Some different color ones in different pots. The tube is there and the top is all curly but it folds in on itself and will not open. Why? I have never had this before. Bev Hope you can make it out in the picture, the white ones show it better than the red or purple.
Try feeding them with a phosphorus fertilizer, such as Bone Meal.
This article has more information.
https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-plant-no-flowers.htm
how to feed and take care of mexican petunias
This article should help. You need to be careful about which variety you buy as some are invasive.