The cache is a small painted lock'n'lock container that can hold small TBs, Geocoins, or other small items.
Remember to jot down the hint for the bonus cache on the container lid!
As this cache is located in an arboretum you will have to find three trees and their information plaques that lead you to the final container. The difficulty may rise in winter when the plaques are buried under snow.
From the recommended parking the path leads through the Rotary Friendship Garden and past the Independence Knoll with the flag pole to the start coordinates. The Prairie Patch which encourages a prairie ecosystem is also located in this part of the arboretum.
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TREE I: N42°03.279 W087°42.314
This is a small tree with showy flowers, light to dark magenta pink in color, that appear in clusters from March to May on bare stems, sometimes on the trunk itself. It grows in the shade and often becomes a dense undergrowth in the forest.
In some parts of southern Appalachia, green twigs from the tree are used as seasoning for wild game. Because of this, this species is known as the spicewood tree in these mountain areas.
Native Americans consumed the flowers raw or boiled, and ate roasted seeds.
Number of letters in the first line on the plaque next to the tree = a
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TREE II: N42°03.249 W087°42.370
This tree is one of the largest of the native trees of the eastern United States, known to reach the height of 190 feet, with a trunk 10 feet in diameter. Its leaves are very distinctive, having four lobes in most cases. The flowers start forming after around 15 years and are superficially similar to a tulip in shape. They have a faint cucumber odor.
Tree fossils have been found in Europe and well outside its natural range in Asia and North America, showing a once circumpolar distribution. The tree apparently became extinct in Europe due to large-scale glaciation and aridity of climate during glacial phases.
Native Americans made their dugout canoes of its trunk.
Number of letters of the first word on the little plaque next to the tree = b
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TREE III: N42°03.223 W087°42.443
This is quite a large tree with a sturdy trunk that stands like a pillar and the branches divide and subdivide into numerous ramifications on which the twigs are fine and thick. In summer these are profusely clothed with large leaves producing large patches of deep shade.
The wood is frequently used as a material for electric guitar bodies, recorders and drum shells, but also for window-blinds and shutters, since it is lightweight and strong.
The tree was a highly symbolic and hallowed tree in Germanic mythology associated with Freya, the guardian of life and goddess of fortune, love and truth. Therefore her tree was considered a tree of peace and it often formed the central meeting place of many villages and rural communities. According to legend it cannot be struck by lightning since Freya is the wife of Thor, a major god of the Germanic pantheon, so it is ascribed protective powers against evil and catastrophe.
Number of the letter "t" you see in the first word of the first line on the plaque next to the tree = c 
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Calculation of the final coordinates:
(a*b*c) + (a*c) + b + b = X
Substract X from the north coordinate of the start point.
(a*b*c*(b-c)) + (a/c) = Y
Add Y to the west coordinate of the start point.
Check your numbers:
c * (a+b) = (a*b) + (a-c)
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This cache / cache series was mentioned in the Chicago Geocacher Podcast - a great show that I highly recommend! Very funny!!