Reabsorbtion. Occuring more commonly within the nephron system than filtration, this is a form of active transport which takes the the useful substances for the body from the tubules and places them back into the blood filled capillaries.
Oleanders are shrubs, but they are _big_ shrubs. Most of the varieties in cultivation top out at 8 to 12 feet tall and about the same width. The wild form, and some of the older cultivars used for windbreaks top out at 20 x 20 feet.
The Moringa Oleifera tree is an extremely fast growing tree that can get to 10 meters. The tree relies on a deep tap root that helps it obtain its nutrients from deep underground. The timber is soft and the plant in the early stages will need support as it will bend over in windy conditions.