Do fruit trees planted in a greenhouse in Stardew Valley gain quality?

I planted one of each tree in my greenhouse on 15 Spring Year 2. It's 8 Summer Year 3, but I'm still getting normal-quality fruit from my trees.

The wiki doesn't mention anything special about trees in a greenhouse. It says I ought to gain a quality rank every year. But I didn't. What gives?

1 Answer

They do gain quality. From the wiki (emphasis mine):

A tree's fruit increases in quality by one star per year of tree age after reaching maturity

A tree needs to grow to maturity which takes 28 days, and then needs to be mature for a year before the fruit quality increases. This means you need to wait until 15/16 Summer for your trees to gain quality if you planted them on 15 Spring.

I have seen the trees in my greenhouse giving silver quality fruit after that period, so there's no exception for trees in the greenhouse to this rule.