[Gardening] Why aren't my plants aging?

Hello Gardeners,
I don't grow many plants in the game but obviously I am doing something wrong and thought perhaps someone here could answer my question.
I have some of the scattered poppies growing (all locked down on benches)but for some reason they will not cycle past 9 days.
They should be on day 12 as of this morning but still are showing 9.
They all are still requiring water and potions but they just aren't growing beyond that 9th day.
Do I need to get some grow lights?

Hi.
They are probably still growing. The day number thing doesn't go past 9, maybe 10 - 18 wouldn't fit in the little square so they made it stick at 9. Sure if you check the resource thing it'll show you 3/8 or so.

Ahh Thank you very much.

Think of it not as "Day 9", but "Growth Stage 9". Once a plant has reached Growth Stage 9, it does not progress beyond that stage but it has matured and will produce seeds and resources every day until it has produced it's maximum.