We suffered the same issue. SE's previous official replies in the past (October 2014) were this:

Crops last at least 24 hours so are good for patch maintenance.
They are looking into making changes to plant timers for longer maintenance.

Obviously point 1 was completely useless as this maintenance was longer than a day yet none of the maintenance notices said anything about "hey, don't grow any plants starting May 5th." (Onions take 10 days, so you couldn't plant starting the 5th)
And point 2....."Please look forward to it" because 2.5 years later they still haven't done a single thing.