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.
Depending on how the plants are to be used and the size of the cultivar, the ideal planting distance ranges from five to ten feet. In the right climate oleander is easy to grow and requires no special care beyond annual pruning and feeding.