This is Brassica nigra, a member of the Brassicaceae family, the mustard family. Members of the Brassicaceae family have four petals, and it was once called the Cruciferae family, referring to the cross-shape of the flowers. [x]

Stachys byzantina, Lamb’s Ear, is originally from Turkey, Armenia and Iran, but has been introduced globally as an ornamental. It is in the Lamiaceae family, which also contains most of the herbs you are familiar with, such as rosemary, basil and mint. It is commonly known as the mint family. [x]

Wheat is in the grass family, Poaceae. It is the third-most produced grain, behind maize and rice. 

Nerium oleander is in the dogbane family, Apocynaceae. It contains several toxic chemicals, including cardiac glycosides. Cardiac glycosides are medicinal in small amounts, but are poisonous in large amounts. [x]

Poison sumac, Toxicodendron vernix, is far more poisonous than poison ivy or poison oak. If inhaled, smoke from burning poison sumac can cause pulmonary edema. This is because of the urushiol, the same compound in poison ivy. [x]

Sudden Oak Death, Phytophthora ramorum, is a devastating disease found primarily in California and Oregon. It is a strange, eukaryotic plant pathogen that causes affected trees to leak dark, gross sap. It is found in oaks, but also other tree species. The above picture shows dead trees among unaffected ones. [x]

Hollyhocks are in the Alcea genus, and their thick roots can be used as fuel for fires. [x]