Pawpaw

Basic Information
Tree ID: 
76
Family: 
Annonaceae
Genus and species: 
Asimina triloba
Description: 
The Pawpaw, otherwise known as the Asimina triloba, is a small tree that bears the largest edible fruit in its native United States. Located close to Hillside Place, the Pawpaw stands (somewhat) tall in the Marsh Botanical Gardens. The Papaw is deciduous and growns as far south as northern Florida, as far north as southern Ontario, Canada, and as far west as Nebraska and Texas. The leaves of the tree grow at the ends of the branches, it grows perfect flowers with six petals, produced in early spring. The fruit of the tree, perhaps its most intriguing aspect, ripen in around September and stay ripe until winter, when it begins to soften and ferment. Sometimes called the "poor man's banana," the Pawpaw fruit has a blend of tropical flavors, including bananas, pineapples, and mangoes and has a custard-like consistency. The fruit is remarkably unsusceptible to insects and disease in comparison to other cultivated fruits, which has made the Pawpaw of interest to organic farmers as it lacks the need of pesticides.
Surveyors: 
Courtney Screen and Kevin Biju
Location
Area: 
Marsh and Farnam Gardens
Collected Data
Tree shape: 
Pyramidal
Date of tree entry: 
02/23/2017
Height: 
5.70 m
5.80 m
Diameter at breast height: 
0.07 m

0.07 m

Bark
The pawpaw's bark is smooth and brown. It is often splotched with wart-like lenticels, which can be observed as light gray patches in the close-up picture. Lenticels are raised pores in that allows gas exchange between the atmosphere and the internal tissues. This is essential for many of the metabolic processes of the woody bark, such as respiration. Interestingly, the tree's bark contains a chemical insecticide which can be used to repel insects that may cause dangerous infections. Some studies have shown that extract from pawpaw can even inhibt the growth of cancer cells!
Twigs & branches
As seen in our tree, the branches can grow throughout the height of the tree, with several starting near the base of the tree. The branches are thus of a spreading pattern. The Pawpaw is a small tree, which can grow up to 12 m. Branches may point towards the sun in shaded sites, thereby creating an open, irregularly-shaped canopy. However, in an exposed location such as that of our tree, the branches do not appear to localize to one direction alone. As seen in the above pictures, the twigs are red-brown with fuzzy, purple-brown buds. The buds were measured to be about 0.6 cm in diameter. The pawpaw can be trained to grow with multiple trunks and its limbs are break-resistant. Some pruning is needed to create clearance because of the drooping of its branches.
Foilage
The leaves of the pawpaw can be classified as simple, alternate with pinnate venation. The leaves appear to be obovate or oblong in shape and are often 12 to 28 cm long and 5 to 8 cm wide. The leaves are normally green in color but turn yellow in the fall. Interestingly, crushing of the leaves will produce a green pepper odor. As seen in the pictures, the leaves of the pawpaw will droop. This is because the leaves are broader at the tip than at the base. This drooping of leaves results in a seemingly wilted appearance. The leaves will fall off in the winter and will remain absent from the tree until after appearance of the Pawpaw's distinctive purple flowers.
Reproductive Structures
The pawpaw species is monoecious, with the organs or flowers of both sexes carried on a single plant. The flowers (observed in another specimen) appear as purplish-brown with a broad bell shape. There is a total of six petals per flower, and each flower is approximately 2 to 4 cm across. During springtime, the flowers tend to appear with or after growth of the leaves. Each flower contains several ovaries, enabling a single flower to produce several fruits. This allows for great amplification of progeny through generations. The pawpaw flower is perfect, having both male and female parts. However, the flowers are also protogynous, a term botanists use to describe when the male and female portions mature at different times. This is an evolutionary adaptation to avoid self-pollination and lead to greater genetic variation in offspring through cross-pollination. Flies and beetles are the main pollinators of the pawpaw. The maroon color and "rancid meat" fragrance of the flower have evolved to attract these pollinators.
Fruit
There are various names for the fruits of the pawpaw: poor man's banana, Hoosier banana, and custard apple.The fruits of the pawpaw are oblong in shape and frequently appear in clusters, with each individual fruit resembling a short, fat banana. They are at first green in color then turn yellow then brown as they ripen in the fall. The fruits attract birds, squirrels, and other small mammals. Consumption of the fruit will lead to dispersal of the seeds in feces. This increases dispersal of seeds so that progeny grow distant from the parent tree. When fully ripe, the edible flesh becomes soft like a custard and will have a taste very similar to that of a banana. The fruits are very nutritious, as it is an excellent source of vitamins A and C, unsaturated fats, proteins, and carbohydrates. Pawpaws actually contain more potassium, phosphorus, magnesium and sulfur than apples, grapes or peaches. Ripe pawpaw fruit have two rows of relatively large, bean-shaped seeds. However, one must be careful, since these seeds can result in digestive problems if consumed.
Seasons
  • Spring
  • Summer
  • Fall
  • Winter
Research
Natural range of distribution: 
Habitat: 
In the map above, the native range of the Pawpaw tree is shown by the purple region, and the area in which temperatures are suitable for its growth is shown by the green region. Thus, the native habitat of pawpaw spans several regions across the United States. Examples of regions include northern Florida to Western New York, the northern shores of Lake Ontario, Southern Michigan to Southwestern Iowa, west to Southeastern Nebraska, and eastern parts of Kansas, Oklahoma and Texas. The pawpaw fruit is the largest edible wild fruit native to the USA. As shown by the map above, they are seldom found near the Atlantic or Gulf coasts. The Pawpaw's preferred habitat is rich, moist bottomland, but the plant will also grow on other well-drained sites. The local habitat should be slightly acidic (pH 5.5-7) soil. They will grow in USDA zones 5A through 9.
Origin, history, and uses: 

The first reference to the pawpaw tree can be seen in the writings of the explorer Hernando DeSoto during his 1541 expedition to the Mississippi Valley. The fruit, which was a favorite food of American Indians, was eaten by the conquistadors led by DeSoto. Later, American settlers used the fruit to make jelly and the tree’s inner bark to string fish. However, the pawpaw fruit is not currently a commercially available fruit. Interestingly, there has been increasing demand for the pawpaw in recent years. Studies have recognized the plant’s potential as a source of organic insecticide.  An insecticide can be made from the tree’s ground-up bark and twigs.This can lead to potential applications in the agricultural industry. The pawpaw tree apparently can also be used for cancer therapy. Extract from pawpaw can overcome the ability of some cancer cells to reject chemotherapy, leading to better targeting of these cancer cells. 

Phenology: 
The budding of the pawpaw is triggered by increasing temperatures and other seasonal changes. The two-inch-wide purple flowers appear before the leaves unfurl in springtime. These changes are then followed by the production of round and oval fruits. The buds of the tree tend break open from mid-April to early-May. During the summer and fall, the pawpaw invests significantly in the forthcoming spring. The conditions throughout the summer, especially in terms of rainfall, affect growth of the pawpaw and subsequent budding in the spring. During the fall, the fruit will ripen. In the fall, the pawpaw builds up reserves of sugar and other essential nutrients in preparation for dormancy during winter. At the beginning of winter (with decreasing temperatures), the leaves will fall off, leading to completely bare branches, as it is a true deciduous tree.
References: 

Virginia Tech Database: http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=155

Carolina Nature: http://www.carolinanature.com/trees/astr.html

University of Kentucky, Department of Horticulture: http://www.uky.edu/hort/Pawpaw

The Journal of the South Carolina Native Plant Society: http://scnps.org/wp-content/uploads/2012/04/Winter_2010.pdf

Southern Group of State Foresters: http://hort.ufl.edu/trees/ASITRIA.pdf

NC State University: https://plants.ces.ncsu.edu/plants/all/asimina-triloba/

U.S. Forest Service: https://www.fs.fed.us/database/feis/plants/tree/asitri/all.html

Keeler, Harriet L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scriber’s Sons. pp. 20-23.

“Pawpaw uses, benefits & dosage.” Drugs.com. 2016. Retrieved 2017-04-26.

Connie Barlow (2001). “Anachronistic Fruits and the Ghosts Who Haunt Them” (PDF). Harvard University Arboretum. Retrieved 2017-04-26.

“Pawpaw”. University of Georgia Cooperative Extension, College of Agricultural & Environmental Sciences, Athens, GA. 2012. Retrieved 2017-04-26.

More
Other information of interest: 

Pollination

Pollination can be a limiting factor in pawpaw fruit set. The flowers are protogynous, meaning that the stigma and pollen mature at different times. Thus the flower is designed not to be self-pollinated. The natural pollinators of the pawpaw, various species of flies and beetles, are not efficient or dependable. Hand-pollination can also be done using a small, flexible artist’s brush to transfer a quantity of fresh pollen from the anthers of the flower of one clone to the ripe stigma of the flower of another clone. An important aspect of cultivation of this tree is to not overburden the tree with fruit, as this will stress the tree, resulting in smaller fruit, thereby causing limbs to break under excessive weight.

Pests

Usually, the pawpaw has few pests of any importance. One pest is Talponia plummeriana, the pawpaw peduncle borer, a small moth larva that can burrow into the flower, causing the flower to wither and drop. This can lead to destruction of many blossoms of the plant. Another pest is Eurytides marcellus, the zebra swallowtail butterfly, whose larvae feed exclusively on young pawpaw foliage.

Media and Arts
This video was a creative portion of our Presentation and was used to provide visual depictions of the tree.

The Pawpaw

The pawpaw grows out in the wood 
      Upon a little tree, 
It has a flavor sweet and good 
      That quite agrees with me. 
Its mushy meat I fain would gulp, 
      ‘Tis soothing to my soul; 
It has brown seeds and juicy pulp, 
      A skin surrounds the whole. 
I meet some folks upon life’s road 
      Who do not like its taste 
And if they had a wagon load 
      Would let them go to waste. 
I might be able to conceive, 
      If I should firmly strive 
How one might be content to leave 
      The pleasant family hive 
And go out in the cruel world, 
      In loneliness to roam 
Where disappointment’s darts are hurled 
      And never think of home; 
Or even how a man might learn 
      To love his mother-in-law, 
But cannot see how one could spurn 
      The glorious pawpaw. 
If I were rich as Morganheim 
      I’d buy a plot of land 
And put in all my leisure time 
      Upon a project grand; 
I’d set it out in pawpaw trees 
      And thus provide a treat, 
That all the folks on land and sea 
      Might have enough to eat.

__Albert Stroud.

The Ohio Pawpaw Festival is a fun-filled and educational community event celebrating one of America’s largest native tree fruits, the Pawpaw (Asimina triloba). This three-day event highlights the rich history and future possibilities of the pawpaw through delectable foods, quality entertainment, unique arts, crafts and local businesses throughout southeastern Ohio and beyond. Special events at the festival include competitions for the best pawpaw, best pawpaw-related work of art, pawpaw cook-off, and the ever-popular pawpaw-eating contest. An energetic family environment is created by Kids Central, which provides a wide range of hands-on activities. The Main Stage is host to some of the best musicians and performers in our region. A full line-up of presentations and activities cover pawpaw growing, cooking, genetics, medical use and other topics related to sustainability.