picked peaches from a farm that were slightly green. what's the best way to ripen at home?
In a single layer out on a shelf or in an uncovered box.
Stacking is no good because they can go bad unexpectedly and the rot can affect the peaches touching the rotten one.
Next time, don't pick them green. The whole point of picking your own peaches is that you can pick them when ripe. Peaches don't ripen after they are picked, although they'll soften some. When picked, they should smell "peachy" and the background color should be yellow, not green. Gently press the stem end. It should give a bit when ripe.
Once you get them home, put them in a shallow box and cover with a towel, to keep the fruit flies away. Check frequently because they go from ready to eat to rotten pretty quickly.
Here in Maine, I am having my best peach harvest ever, after getting exactly none last year.
Peaches are a climacteric fruit which means they do ripen after picking through the release of ethylene and carbon dioxide increasing the sugars. With that being said there is a wide range within climacteric fruits of when you can pick them after they've reached their mature size and still expect a reasonable release of ethylene and carbon dioxide and thus to ripen further. At one end of the scale is bananas which can be picked very green and fully ripen. At the other end of the climacteric scale would be figs which must be picked within a dau or two of full ripeness to ripen further. Peaches are about in the middle. You really should never pick when there is more green than yellow but when there is more yellow than green and at least the hint of the smell of a peach.
Some examples of non-climacteric fruits that do not ripen after picking would be grapes, cherries, limes, pineapples.
I should also say that ripening on the counter through the release of ethylene and carbon dioxide is not a good substitute for hang time on the tree. The ripest fruits will always come from hang time on the tree.
Thanks for the tips and info. Tree ripened is definitely best. Unfortunately our local farm opened up peach picking a bit too early this year, and once we were there I couldn't disappoint our 3yr old! We tried ripening on a table top with a dish cloth underneath and on top. Didn't work that well, which probably validates David's comments above. I ended up turning them into a deliciously tart jam.
brown paper bag is the best way I know of. haven't bought green peaches in decades...