I am making an ale flavored with juniper berries (dried and crushed). I am considering adding some during secondary, much like dry hopping.
What I want from the berries is of course the resinous and bitter tastes, i.e., essential oils in the berries, in addition to some other flavors. Will adding the berries like this impart anything at all?
If you do this you should soak them in a little bit of vodka - effectively making a tincture.
There are three reasons why:
control: The alcohol will leach the essential oils and you can add the tincture a little bit at a time until you reach the flavor you want
sanitation: Juniper berries especially can be used as a fermentation starter as they have a specific kind of yeast on them that has particular qualities. One example of this is Smreka, but there's a Finnish drink called sahti and various experiments around - that to say, you don't want to introduce an uncontrolled yeast at this stage.
easier racking/cleanup: Pouring liquid into the secondary means no yeast-covered berries to pull out when you rack.
I do not see why it would not extract some of the alcohol and water-soluble compounds (flavors) from the berries at that stage. The essential oils would probably come out more easily at this point than if you tried to extract them during primary fermentation, due to the higher alcohol content and typically better solubility of essential oils in alcohol. However, ale typically has a relatively low alcohol content compared to what I typically ferment (sake in the primary, 12% ABV kit wine in the secondary), so I have little experience with low alcohol fermentations.