Monday, June 3, 2013

Names That Make Kids Laugh - Pawpaw

I have mentioned in several previous posts that there are certain common names of species that seem guaranteed to make people, especially children, laugh.  One of the programs that do with elementary students is a leaf identification activity.  The students are given a packet of leaf sample and have to identify needle-leafs and broadleafs, simple and compound leaves.  There are always two species of tree that elicit laughter among the students.  The first of these is the American Bladdernut (Staphylea trifolia) - for obvious reasons if you are a third grader. 

The second one is the Pawpaw (Asimina triloba).  At least one student per class always seems to yell out "Pawpaw!  There's a tree called a Pawpaw!" upon discovering it in their packet of leaves.  There is just something about the repeated sound in the name Pawpaw that just elicits smiles and laughter.  Perhaps its because most kids (and adults) in Mid-Michigan have never even heard of the Pawpaw, much less seen one.

So why don't people know about this plant?  We have a town in the southwest part of the Michigan named Paw Paw, but I would guess that the majority of people in the state do not know that the town is named after a tree.  Here in Mid-Michigan the Pawpaw tree is very rare.  According the USDA PLANTS Database, the Pawpaw is only found in the bottom four tiers of counties in Michigan (extending up one more tier along Lake Michigan). 

Michigan County Distributional Map for Asimina triloba
Distribution of Pawpaw in Michigan according to the US Department of Agriculture

Mt. Pleasant is located in Isabella County in the sixth tier of counties - literally in the "Middle of the Mitten".  According to the USDA, the Pawpaw is not found here, but there is a large patch located right in the middle of town.

 Pawpaw patch - Mill Pond Park, Mt. pleasant, MI

The Pawpaw is found in moist soils in deciduous forest and floodplains from the Great Lakes south to the Gulf of Mexico, from the East Coast west to the the eastern edge of the Great Plains.  An understory tree, the Pawpaw grows to a height of between 20 and 30 feet on average.  Some larger specimens attain 40 foot in height.

"Pickin’ up paw paws,
Put ‘em in your pocket
Way down yonder in the paw paw patch"

The traditional American folk song "(Way Down Yonder in the) Paw Paw Patch references two characteristic features of the Pawpaw - its fruit and its habit of growing in dense patches.  The Pawpaw produces a 3-5 inch long fruit that falls from the tree before ripe.  The fruit ripens on the ground, hence the song lyric "pickin' up paw paws".  This fruit has a distinctive tropical look and taste - the Pawpaw is the northernmost representative of a group of tropical and semi-tropical fruit trees that include the cherimoya, custard-apple, and soursop.  The Pawpaw is often the Wild/Michigan/West Virginia/Kansas/Poor Man's/etc. Banana for its similarity to a tropical species.  It is not only the fruit that gives this plant a tropical appearance.  Its large, simple, obovate leaves can reach up to a foot in length - Obovate means that the leaf is egg-shaped with the widest part of the leaf closer to the tip than stem.  There is no other leaf in Mid-Michigan that resembles that of the Pawpaw

Pawpaw (Asimina triloba) flower and leaves

The flower is also quite unique for a tree in the northern United States.  It is large (1 to 2 inches across), but drab colored.  This deep red-purple bloom is shaped like a bell with six petals and hangs downward from the branches.  Like most large flowers it relies on insects for pollination.  The flowers have the unpleasant aroma of rotting meat and attract insect species that feed on carrion (flies and especially beetles).  This color and odor combination appears to be common among species that rely on flies or beetles for pollination.  Other local plant species that utilize this color/smell combination include Skunk Cabbage (Symplocarpus foetidus) and Wild Ginger (Asarum canadense).  The Pawpaw flower can be found in late-May through June.

Pawpaw flower - the mottled flesh-like coloring and carrion smell attract flies and beetles
Underside of Pawpaw flowers - note three large petals surrounding three smaller petals

Pawpaw (Asimina triloba) flowers

Pawpaw (Asimina triloba) flower

Because the tree relies upon insects for pollination fruit production can be spotty at times.  In the nearly ten years that I have known about the local grove of Pawpaws, I have seen exactly one fruit that grew to any size.  That fruit grew to about 1.5 inches before disappearing from the tree - I do not think this fruit fell from the tree and ripened, it was quite early in the summer for that to happen.

Even without setting fruit, this plant spreads outward from the mother tree by sending up clones from the roots.  Over time, Pawpaw patches become quite dense with trees of multiple ages and sizes radiating from the center of the patch.

If you are walking through the woods anywhere in eastern North America and find a grove of tropical looking trees, you've probable wandered "way down yonder in the paw paw patch".

Basic Information

Asimina triloba

Height:  20-30’ tall

Habitat:  moist soils, floodplains, deciduous forests

Flower:  reddish-purple, 1-2” wide

Fruit:  berry-like, green turning yellow to brown or black,  3-5” long

Fall Color:  yellow

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