Cleistocactus strausii
The cactus prefers free draining soils, strong sunlight, but not high temperatures — in fact it can withstand hard frosts down to -10 °C. In its natural habitat it receives plenty of water during the summer, but almost none over the winter. In cultivation, watering too much in winter often leads to root rot.
Sudbury River
Water caltrop, more commonly known as water chestnut, species "Trapas natans", is an invasive waterplant from western Asia. The initial introductions in the U.S. were in the 1870s in Cambridge, MA, followed by deliberate introduction into ponds near the Concord and Sudbury Rivers. This is now an invasive, habitat-destroying plant across many of the eastern states. On the Sudbury River, OARS (Organization for the Assabet, Sudbury and Concord Rivers) organizes annual plant pulling events. Volunteers in canoes hand-pull the surface-floating rosettes of leaves and nuts before the nuts mature and fall to the bottom. The infestation on the Sudbury River is particularly bad between the Fenwick Street and Saxonville dams, where the water surface can be more than 80% covered.