I thought this weed resembled watercress so I did a little research. It is hairy bittercress, or Cardamine Hirsuta. The name fits it perfectly, as the leaves have little hairs (hirsutus is latin for hairy). It is in the mustard family and is an edible annual herb/weed. I tasted it and find it very similar in flavor to kale!
The larger leaves are peppery and bitter so if you’re inclined to try it, go for the younger, smaller leaves. The whole plant is edible, including the leaves, seed pods and flowers. Don’t indulge if you’re unsure of pesticide use in the area.
It is rather invasive. When trying to eradicate it, it’s best to pick the whole plant up by the roots while the soil is wet from rain. Preferably before it flowers and sets seed. The seed pods are the little pods that look like leafless stems (as in photo below).
I had a bunch growing in my little kitchen garden, until a natural weed eater came along. Deer!
Oops, almost forgot the best part! Although I couldn’t find nutrition data for hairy bittercress, I did find some stats for garden cress (in the same family, Brassicaceae). Just one ounce of fresh cress provides 39% recommended daily allowance (RDA) for Vitamin A, 32% RDA for Vitamin C, a whopping 190% RDA for Vitamin K as well as trace amounts of other vitamins and minerals. It also delivers small amounts of omega-3 and omega-6 fatty acids.