More perennials from the 91st Street Garden. Today, we have Lupinus perennis, or lupine.
Lupines are easy to identify in a garden, due to the large, palmately compound leaves and the tall spikes of pea-like flowers. Indeed the flower structure is a clue as to which family this plant belongs: Fabaceae, or the pea, or legume family.
Like most plants in the Fabaceae or Leguminosae family, Lupinus can fix its own nitrogen. Most of the nitrogen in the environment is released into the atmosphere as a gas when organic matter dies and decays. Plants generally need to have this nitrogen 'pulled' out of the atmosphere in order to benefit from the element. Legumes are unusual in that they have bacteria on the roots that form nodes. These nodes are able to harvest nitrogen from the air.
(An aside: this is why clover and alfalfa, other legumes, are used in crop rotations. Those nitrogen-rich plants can provide extra fertilizer in the soil when they are tilled over.)
The plants ability to fix nitrogen also accounts for its botanical name. Lupinus is derivative of the word for wolf. The belief was that this plant was stealing nitrogen from the soil, like a hungry, greedy wolf.
The flower itself, like other pea family plants, has two upper 'standards' and two lateral 'wings.' The lower petals form together to make a 'keel.' The overall effect is that the plant looks much like a bonnet, which accounts for another common name for Lupinus: bluebonnet.
This red cultivar above is from the New York Botanical Garden.
Lupines have seeds that are highly poisonous. In fact, there has been a historical problem with cowboys and ranchers seeing their livestock die in massive numbers when the unknowing cows and horses grazed on the native lupines so prevalent in the west.