Horsetails, not Marestails. Horsetails are of very ancient lineage and giant ones (over 30 metres tall) feature much in coal measures from the Devonian epoch. today, the tallest species reach around 4 metres (in central and south America). The illustrated plants are the reproductive structures which produce spores, not pollen; they are not flowers. Marestail is an aquatic flowering plant, Hippuris vulgaris.
Comiserations, if you have an infestation of Equisetum arvense; it's a quickly-spreading, smothering weed and very difficult to control. Plenty of advice on that on line, though.