The later hail occurs in the season, the more damage it can do to yield. While canola can keep flowering to compensate from hail that occurs during flowering, hail at the late pod stage can result in unrecoverable yield loss.
Yes, hailed plants that seemed to be past flowering can start to regrow, going through flowering stages again. With enough time, new branches can produce enough yield to make harvesting worthwhile.
Time and moisture are the best treatments for hailed crop. While we’d like a product to assist in hail recovery, to date it appears a well developed root system, moisture and time are all we can count on.
If applying any treatment on hail-damaged crops, keep in mind that there is very little research available on the efficacy of any product for this purpose. Leave appropriate check strips in order to make an accurate yield comparison at harvest. Note pre-harvest intervals if applying a fungicide.