Why not a 'perpetual growth' deed?
It would make it so a day 9 plant with 0 seeds/resources able to be grown/harvested stays at day9, so it counts as a decorative that can still have pollen collected.
Another idea, and I already see the problems in it, is a seed harvester that turns a decorative plant into the seed that produced it.
Plant BOD Reward sugg
Re: Plant BOD Reward sugg
I appreciate your suggestion, but no 
Re: Plant BOD Reward sugg
Out of interest, will the plant BOD's call for both decorative, and still growing plants?
Character name: Ebony