I live in central Alabama, my lemon grass was left outside in the ground this past winter. I have not seen any green leaves from this plant as of today April 28,2018. Can you tell me how to revive this plant?
Most of your area is outside of the natural growing zone of the grass, and will only be able to be grown as a perennial. This article will help you on the care of this: https://www.gardeningknowhow.com/edible/herbs/lemongrass/learn-about-growing-lemon-grass-plant.htm
My lemon grass does not get bulbous like a green onion at the base_- from the ground up it's mostly the shape of the leaf. I never have the white part to harvest only abundant green leaves . However the plant does well in size and is quite attractive. How do I get thick edible part to grow ?
Even the varieties with the largest pseudo bulbs do not get very big. You can expect an inch or two in length, and maybe at most, an inch across, but this would be rather large and take a few years to achieve.
This article will give you more information on their care: https://www.gardeningknowhow.com/edible/herbs/lemongrass/learn-about-growing-lemon-grass-plant.htm
The compost is fine... It needs to be mixed with potting soil, though. It doesn't appear to have any aeration, and it is likely much too strong for a grass. I would mix it into a potting mix at 1/3 strength, and work from there, adding a handful every few weeks.
This article will give you more information on the care of lemongrass: https://www.gardeningknowhow.com/edible/herbs/lemongrass/learn-about-growing-lemon-grass-plant.htm
How do I know "when" to propogate? Purplish stalks? Brown?
These articles will help you.
https://www.gardeningknowhow.com/edible/herbs/lemongrass/harvesting-lemongrass.htm
https://www.gardeningknowhow.com/edible/herbs/lemongrass/cut-back-lemongrass-plants.htm
I went out to look at my lemongrass and water plants to find a ton of it with these white rain drop shaped spots surrounded by black. see photo for details. what is it and how do I fix it?
This is a type of rust that, typically, effects Bluegrass. This will be best controlled with dolomitic lime, and wettable sulfur, or instead you can use copper fungicides. I tend to lean towards the first option due to less toxicity, but the second option is stronger.
Although this is not the same rust species, it is very similar in how it spreads, and how it is controlled, so this article will help: https://www.gardeningknowhow.com/edible/herbs/lemongrass/brown-leaves-on-lemongrass.htm
is lemongrass related to sugar cane?
They are in the same family, but not the same genus. This means that they are close enough to be similar, but not close enough to cross pollinate.
We live in South Australia and have a lemongrass plant that has beautiful healthy looking grass but the stalks just don't seem to develop. What should we be doing to encourage the stalks to thicken up?
It is possible that they need fertilization, but it is also likely that the soil is too compact for good growth. There are many reasons that this could be the case, unfortunately. Here is an article that can help you to care for these properly: https://www.gardeningknowhow.com/edible/herbs/lemongrass/learn-about-growing-lemon-grass-plant.htm