I have a veggie garden in my backyard and it's growing fast. I mixed compost in with the soil. Now that the plants are getting big, I'm having a problem with this white residue on the leaves. It looks like someone threw flour on the plants, and I don't know what it is and how to get rid of it.
The white residue is powdery mildew. Here is an article or two that you may find helpful: https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
Severe browning at roots of perennials--water, disease or pest? What is the most common cause?
It sounds like it may be crown rot. This article will help:
https://www.extension.iastate.edu/publications/sul8.pdf
I have a full sun front of the house spot. Everything I plant there does not grow. It dies. I tried adding Miracle grow, watering, etc. Nothing happens. What can I do? There is a shrub there that seems to stay alive. How do I fix this problem?
That part of your yard may have trouble retaining water due to the high heat because of the full sun. You should look at xeriscaping, which needs less water and can take high temps. Here is more information on this style of gardening: https://www.gardeningknowhow.com/xeriscape
I am noticing a white powder (not mold or mildew) on my plant leaves. It has spread to other plant leaves. What is it, how do I get rid of it, and can I still eat the vegetables?
Sounds like powdery mildew. The vegetables are fine to eat with thorough washing. The following article should be of some help to you: https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
Are one of the symptoms of root rot what looks like whitish powder?
No, the white powder is probably powdery mildew, which thrives in the same conditions that root rot does. These articles will help:
https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
Why do the leaves of my plants go brown at the edges?
This article will help you with that: https://www.gardeningknowhow.com/plant-problems/environmental/what-causes-brown-edges-on-leaves-of-plant.htm
How do you control rust?
This article should help: https://www.gardeningknowhow.com/plant-problems/disease/learn-about-plant-rust-disease-and-rust-treatment.htm