THE AMAZING PAWPAW TREE

‘ God has cared for these trees,

saved them from drought,

disease, avalanches and a

thousand tempests and floods.

But he cannot save them

from fools.’

John Muir

 

 

Out of all the plants we grow, the pawpaw is the most sought after. Its popularity lies in its uniqueness and scarcity. There are limited pawpaw in the wild, and it seems, fewer seeds to be obtained from true Ontario cultivated stock. Add to this that the pawpaw has the most involved germination requirements. These factors, when combined, create a scarcity of pawpaw for purchase.

But why do people want pawpaw? The answer is simple, uniqueness. In every aspect, pawpaws are unique and are like a crown jewel in anyone’s garden collection. Even the name, Asimina triloba, sets the plant aside. Asimina translates to ‘ food of the gods ‘ and refers to the strange mango looking fruit produced. Triloba refers to the strange three lobed flower.

This tree was a hugely popular tree for the native inhabitants of North America and when the Spanish started to explore the Mississippi valley, back in 1541, the Conquistadors named the fruit ‘ pawpaw ‘ after the Spanish word papaya. This tree, native to North America, produces the largest edible fruit. It was the major source of fruit for the native American since the present day apple was brought from Britain in 1625. Hard to believe the cultivated apple tree is not native.

How do I explain how the fruit tastes? Like nothing you have ever tried! Actually, the family name that the pawpaw belongs to hints as to the taste of the fruit. The apple custard family.

In the wild, these trees grow in thickets in the forest understory and along woodland edges. They prefer fertile soil that is well drained. The amount of sunlight will determine the shape of the tree where dense growth is typical of sunny conditions and a more open growth is indicative of shady conditions. They have moderate growth rates and will attain heights of 15 – 20 feet and widths of 15 – 20 feet.

Unfortunately, people stopped seeking out pawpaw in the forest when apple tree cultivation became popular. At the same time, massive deforestation for land colonization happened which vastly decreased populations and left only scattered remnants of pawpaw. Finally, this tree is coming back to popularity. There is renewed interest since there is potential for organic insecticides from its ground up bark and leaves. Also, extracts from pawpaw can overcome the ability of some cancer cells to reject chemotherapy.

You would assume, with this renewed public interest in this tree that propagation and growth of pawpaw would be embraced by the horticultural industry. – Nope. Again, it comes down to the uniqueness and challenges of growing these plants. The first hurdle to propagation is the flower biology and fertilization. The flowers are lovely in color, maroon, and 2 inches wide. But the flowers are self incompatible which means that the flowers cannot pollinate themselves but must be cross pollinated.

Many plants are self incompatible and manage to get pollinated. The key to the pollination puzzle lies in which pollinators are attracted to these lovely flowers. In nature, flower shape, color and smell are all carefully designed to attract the appropriate pollinator that will be the most efficient at pollination. Believe it or not, bees show absolutely no interest in these showy flowers. It is flies and beetles that are the required pollinators. The flowers are attractive to the flies and beetles by both their color and aroma. The maroon coloring mimics the look of rancid meat and the aroma is not pleasant, again, mimicking rotting matter.

For some reason, flies and beetles, are not consistent as pollinators. In the wild, pawpaw have low seed set. The pioneers were quite inventive. To overcome this issue, they would hang road kill at 8 foot intervals throughout the trees to maximize flower appeal and increase pollination rates. I could see my neighbors taking offense to these pollinator techniques!

I’ve already mentioned that pawpaw have one of the most complicated germination requirements. There are several months of warm conditioning followed by several months of cold stratification. And of course, it is all about careful timing that the end of the cold treatment coincide with spring planting. Even the planting of germinated seeds requires more thought and precision.

But no matter what the difficulties, be sure to plant these trees. Once established, they are self sufficient. They are generally pest free, drought resistant and will multiply by suckering to create a lovely thicket. Even though pawpaws look exotic and have beautiful flowers, I planted them for the butterflies. The pawpaw is the only larval plant for the zebra swallowtail butterfly. Since there are few pawpaw we now have few zebra swallowtail butterflies.

Whatever your reasons, be sure to plant the lovely and unique pawpaw.