There isn't really much of a time scale, but I'll tell you how long I think things will take.

(5 hours) Organizing information for the index, obtain 2 pictures for each plant, redesign typing aesthetic , spell check, check sources.
(.5 hours) Make sources in MLA format
(1-4 hours) Work on redesign for the garden to scale, finish all hardscaping and critiques
(2 hours) Research more about ecosystem and type a coordinated paper
(2 hours) Finish legend with colors, well typed descriptions and information
(1 hour) Research Resource Needs and write a description