In the UK the two common species that you are likely to have come across are, Broad-leaved dock (Rumex obtusifolius), and Curled dock (Rumex crispus), which in the US is called Yellow dock.
According to Frank Cook it’s famous for its ascorbic acid content and was used in the past to treat scurvy. Useful also combined as a herbal tea mix.
Dock is edible all year round. However as Frank points out, we are all individuals (bio-individuality) and as a result what is flavoursome to one person may not be to another. It all depends on how much you have integrated wild foods into your own diet.
Personally I have found that my sense of smell and taste have radically changed since I started consuming wild foods. So remember to take it nice and slow, and play with the abundance of wild foods that you find locally.
In this 2 part video series Frank Cook discusses the many uses of edible docks as wild food and herbal medicine.
Video No. 1
Video No. 2