What is this disease and how do you treat it? It is on azaleas and rhododendrons and the main branches just look black like they have been in a fire. What is this?
I believe you have what is called "sooty mold". For more information and recommended treatments, please visit the following links:
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/rhododendron-sooty-mold.htm
I live in the marsh. Can azaleas be planted close to the marsh, which is sometimes covered in saltwater?
Unfortunately, azaleas are one of those plants that do not tolerate salt water. However, here is an article that will give you salt resistant plant choices:
https://www.gardeningknowhow.com/special/seaside/gardening-salt-water-soil.htm
It looks like a green mold on the branches, not leaves, and going from bush to bush.
I suspect that the "green mold" you have on your azalea branches is actually lichen. Touch it - is it relatively hard and crusty in appearance? If so, no action on your part is necessary as lichen are not harmful. If you want to remove it, it can be removed, gently, with a soapy solution.
For more information on lichen, please visit the following link:
https://www.gardeningknowhow.com/ornamental/fungus-lichen/treatment-tree-lichen.htm
Going over to mums for Mother's Day, and bought a new big ceramic pot for her azalea. Can we repot it now, as it has new buds all over, or is this too early for them?
The general rule of thumb is to not re-pot a plant when it's in bloom. It is advised to wait until after flowering. The stress of re-potting may hinder the azalea's flowering attempt. Also, during re-potting, you run the risk of flower buds dropping off.
For more information on the care of azaleas, please visit the following link:
https://www.gardeningknowhow.com/ornamental/shrubs/azalea/azaleas-noteworthy-shrubs-for-any-garden.htm
What causes an azalea bush not to bloom two years in a row? For two years now my azalea bush has not bloomed any flowers but the bush looks healthy and is growing.
The soil may either have too much nitrogen or too little phosphorous. These both cause plants not to bloom. Have the soil where they are tested to see which it is and then amend the soil accordingly.
These articles will help you:
https://www.gardeningknowhow.com/plant-problems/environmental/plant-not-blooming.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/phosphorus-plant-growth.htm
Azalea dying slowly. Leaves are turning brown and crunchy. Flowers around bottom of plants and just a few leaves randomly spread over plants. I have three plants and they all look the same. Leaves are sometimes black on the tips and creeping towards the green sections.
The description could be insect damage, disease or environmental damage.
Here is an excellent article that may help you pinpoint the issue.
https://www.gardeningknowhow.com/ornamental/shrubs/azalea/common-azalea-problems.htm
Do the dead flowers need to be deadheaded for new growth?
Azaleas do not get a second wind of blooms in one season, therefore, deadheading would be done to improve the appearance of the bush as well as directing energy towards flower bud production for the next blooming season.
For more information on trimming/pruning azaleas, please visit the following link:
https://www.gardeningknowhow.com/ornamental/shrubs/azalea/pruning-azaleas.htm