The times for growth don't double without Green Thumb instead they seem to be grouped around various growth times.

Planters:

Apples: Cutting available 19 hrs after planting Harvestable 81 hrs after planting

Grapes:Cutting available 28 hrs after planting Harvestable ?? (game crashed) *so longer than 85 hours

Carrots:Cutting available 7 hrs after planting Harvestable 31 hrs after planting

Mushrooms: Harvestable 59 hrs after planting

Parsley:Cutting available 12 hrs after planting Harvestable 31 hrs after planting

Daisy:Cutting available 14 hrs after planting Harvestable 58 hrs after planting

Chrysanthemum: Cutting available 14 hrs after planting Harvestable 59 hrs after planting

Ground:

Apples: Cutting available 19 hrs after planting Harvestable 85 hrs after planting

Grapes:Cutting available 28 hrs after planting Harvestable ?? (Game crashed)

Carrots:Cutting available 7 hrs after planting Harvestable 31 hrs after planting

Mushrooms: Harvestable 59 hrs after planting

Parsley:Cutting available 7 hrs after planting Harvestable 31 hrs after planting

Daisy:Cutting available 12 hrs after planting Harvestable 58 hrs after planting

Chrysanthemum:Cutting available 14 hrs after planting Harvestable 59 hrs after planting

While I haven't posted the exact minutes as well, the planters gave a few minutes bonus but no more than 30 mins faster. So for example the exact timing for Daisy in a planter was 57 hours and 54 mins, I rounded it up to 58 hours.

Where the difference was really seen was how long it took the plants to actually grow the produce. The times above are from the first produce on each plant. From there I timed it till each plant had all 10 produce available.

Parsley and carrots took 41 hours to have 10 harvestables growing on the plant in a planter.

Parsley and carrots took 47 hours to have 10 harvestables growing on the plant in the ground.

While it's not much of a difference , it is enough to make a difference in the long run if your sim harvests each plant at the optimal time.

I've run through this scenario a few times and couldn't exactly replicate these times... *shrug* least these times will give a rough guesstimate until you go through it yourself Carl. Each time I used normal plants and a new sim with no traits or emotions that would help with gardening in an obvious way. Unfortunately I didn't include grapes until my last try and I'm a bit over watching plants grow for now... it's kinda like watching paint dry.