Mike......why not expend your energy on a Blog ?
A book such as you describe has been done so many times before and the publishing world these days is a cut throat industry. You will at the very least need an editor and then either you or your agent will need to tout your finished work around the publishing houses.
Self publishing (in hard format) can be rather expensive.
You could maybe look at self publishing in electronic form...........won't cost you and you may earn a few bob if your book attracts attention.
Not trying to rain on your parade........these are just a few thoughts for you to consider...........gardener's "diaries/experiences" are always interesting to like minded people but the format isn't new and there is a lot of competition out there these days.
You can get a lot of pleasure from just recording your experiences and ideas and leaving for your family and friends.......or just posting on various forums.
Hope you are still recovering well from your op