can you freeze herbs for distilling?

I can't think of any reason one couldn't freeze herbs for later distillation for hydrosol and essential oils. I googled a bit but didn't turn up anything really pertinent. Any thoughts appreciated!

I don't think freezing changes the molecular structure of the herbs, the ice crystals pierce the outside of the plant cells here and there, but that might enhance the extraction.
When i made rosemary balm and watched videos about it, people gave contrary advice on drying it, or not drying it, before putting it in oil. I did both and prefer not drying it,straight in the oil, because the oil smelled stronger afterwards.
Try it and let us know please.

I haven't researched other medicinal herbs but I did look into the effects of heating, freezing and drying on elderberries' medicinal qualities for my elderberry book and found that freezing was found to diminish those over time.  

Someone asked about this recently on my web site so I'm copying and pasting my answer to her:

Frozen elderberries can be used but they will not have as much medicinal benefit as fresh or dried. I have a section in my elderberry book where I researched the effects of heating, drying and freezing on various properties in elderberries. Here’s a clip about freezing:

“The Journal of Agricultural and Food Chemistry published one study that investigated the effects of freezing on the levels of anthocyanin (a component of elderberries and other fruits which studies have shown has anti-viral, anti-inflammatory, antibacterial and anti-cancer properties, among many other health benefits) on three varieties of American elderberries (Adams II, Bob Gordon, and Wyldewood).
The researchers concluded that the variety of elderberry shrub influenced the amount of anthocyanin in the berries (factors such as elevation also affect the content), with some varieties holding up to freezing better than others, and all varieties retaining more of their healthy properties with shorter freezing times rather than long ones:

‘The Bob Gordon retained 99%, 76%, and 58% of its initial anthocyanins during 3, 6, and 9 months of storage, respectively. Wyldewood retained 72%, 44%, and 28% and Adams II 42%, 30%, and 18% of their initial anthocyanins during 3, 6, and 9 months of storage, respectively.’

The authors also acknowledged that they thawed and re-froze the elderberry samples for each testing, and this process could have contributed to the breakdown as much as the freezing itself, too.

Of course, all of these are commercial varieties of elderberries, and your wild elderberries are going to have unknown amounts of anthocyanins and unknown reactions to freezing. This is a good study to give you an idea of the potential effect, though.

The takeaway for freezing elderberries:

All elderberries will lose some of their medicinal properties during freezing, but they will lose less if you freeze them for a shorter time (such as three months or less). The longer elderberries remain frozen, the less they will retain their medicinal properties.

If you plan to purchase elderberry seedlings to grow your own elderberries, the Bob Gordon variety seems to be the best bet for health benefits.”

So your elderberries will probably lose some of their value from freezing but keep in mind that elderberries are so packed with benefits that a tincture from frozen berries would still be very helpful. I would use a very high proof alcohol for the tincture with frozen berries though, since it will be somewhat watered down from the freezing and thawing. Frozen berries make a wonderful elderberry liqueur and schnapps, too, and then the medicinal benefits are just extra.  ;)

Here's the original page where the discussion was going on.

One thing I wondered is if the longer freezing time is what diminished the anthocyanins or the process of thawing and freezing itself.  I kind of suspect that it was the latter that made the biggest difference.  I'd like to see a study where they just left some alone and measured levels after a few months and then again after a year.

Anyway, I thought that might be helpful.  I do know that many herbs are best dried first and then used for tinctures.  I know you're asking about distillation and not that, but it all seems somewhat related.

Not sure if that helps any at all but there you go!  :)

Thanks Alicia.... Those are significant differences for the different time periods. I wonder what temperature they were frozen at as most everything that goes in the freezer has a longer freezer life the colder the temps are. I also wonder about the freeze/thaw/re-freeze cycle and how much it was in play.

Any storage method is going to be imperfect, my understanding is that the most valuable medicinal compounds tend to be highly volatile and thus will oxidize or otherwise deteriorate relatively swiftly. Fresh is always better with medicinal herbs but it really depends on what your situation is. Is it either, freeze some herbs and make some (possibly slightly weaker) essential oil or don't make any oil? If so I would just freeze some herbs, make some oil, gain some experience and have fun. From my research into storage of herbs it seems that the absolute best option for long term storage of perishable medicinal herbs would be to freeze dry them and then vacuum seal the freeze dried herb with oxygen absorbent packets. This is, of course, prohibitively expensive for a hobby but as a sort of ideal to short for it could inform your storage choice. For practicality I would think about vacuum sealing with the oxygen packets and then freezing.