Yes, well maybe ehhhhhh.
Ok I have frozen dandelions for longer periods and that works fine.
I also have frozen rose petals for a longer period, which also works fine. Rose petals however tend to oxidise in the long run, which shows by them getting brown. So if they start to get brown it is time to start making wine. It will take a few months to get to that stadium.
I am at this moment doing a test with frozen elderflowers. Looks promissing however I hope to bottle before my holliday so I can give you the results. In the mean time: freeze them, better as throwing away........
Keep an eye on my web-log, because if I can still find the time I will post the results of my frozen elderflower wine there before I go on my holliday to France.