American Papaw (Asimina triloba)

Common Pawpaw, Pawpaw

The aromatic pawpaw fruit has a tropical flavor, resembling creamy custard made from bananas, pineapples, and mangos. The tasty fruit is popular with raccoons, birds, squirrels, and other wildlife as well as man. Ornamental qualities include an attractive shape that can be pyramidal or conical, and leaves that often turn brilliant yellow in autumn before dropping from the tree. Pawpaw tree care includes watering to keep the soil moist, a regular schedule of fertilization, and in most cases, hand pollination of the flowers.

I. Appearance and Characteristics 

Asimina triloba, the American papaw, pawpaw, paw paw, or paw-paw, among many regional names, is a small deciduous tree native to the eastern United States and southern Ontario, Canada, producing a large, yellowish-green to brown fruit. Asimina is the only temperate genus in the tropical and subtropical flowering plant family Annonaceae, and Asimina triloba has the most northern range of all. Well-known tropical fruits of different genera in family Annonaceae include the custard-apple, cherimoya, sweetsop, ylang-ylang, and soursop.

A. triloba is a large shrub or small tree growing to a height of 35 ft (11 m), rarely as tall as 45 ft (14 m), with trunks 8–12 in (20–30 cm) or more in diameter. The large leaves of pawpaw trees are clustered symmetrically at the ends of the branches, giving a distinctive imbricated appearance to the tree’s foliage.

The leaves of the species are simple, alternate and spirally arranged, entire, deciduous, obovate-lanceolate, 10–12 in (25–30 cm) long, 4–5 in (10–13 cm) broad, and wedge-shaped at the base, with an acute apex and an entire margin, with the midrib and primary veins prominent. The petioles are short and stout, with a prominent adaxial groove. Stipules are lacking. The expanding leaves are conduplicate, green, covered with rusty tomentum beneath, and hairy above; when fully grown they are smooth, dark green above, and paler beneath. When bruised, the leaves have a disagreeable odor similar to a green bell pepper. In autumn, the leaves are a rusty yellow, allowing pawpaw groves to be spotted from a long distance.

Pawpaw flowers are perfect, about 1–2 in (3–5 cm) across, rich red-purple or maroon when mature, with three sepals and six petals. They are borne singly on stout, hairy, axillary peduncles. The flowers are produced in early spring at the same time as or slightly before the new leaves appear, and have a faint fetid or yeasty smell.

The fruit of the pawpaw is a large, yellowish-green to brown berry, 2–6 in (5–15 cm) long and 1–3 in (3–8 cm) broad, weighing from 0.7–18 oz (20–510 g), containing several brown or black seeds 1⁄2–1 in (15–25 mm) in diameter embedded in the soft, edible fruit pulp. The conspicuous fruits begin developing after the plants flower; they are initially green, maturing by September or October to green, yellowish green, or brown. When mature, the heavy fruits bend the weak branches down. Full ripening often happens only after the fruit falls naturally, thus signifying a seed dispersal strategy aimed at ground-based, rather than arboreal, mammals.

Other characteristics:

  • Calyx: Sepals three, valvate in bud, ovate, acuminate, pale green, downy
  • Corolla: Petals six, in two rows, imbricate in the bud; inner row acute, erect, nectariferous; outer row broadly ovate, reflexed at maturity; petals at first are green, then brown, and finally become dull purple or maroon and conspicuously veiny
  • Stamens: Indefinite, densely packed on the globular receptacle; filaments short; anthers extrorse, two-celled, opening longitudinally
  • Pollen: Shed as permanent tetrads
  • Pistils: Several, on the summit of the receptacle, projecting from the mass of stamens; ovary one-celled; stigma sessile; ovules many
  • Branchlets: Light brown, tinged with red, marked by shallow grooves
  • Winter buds: Small, of two kinds, the leaf buds pointed and closely appressed to the twigs, and the flower buds round, brown, and fuzzy
  • Bark: Light gray, sometimes blotched with lighter gray spots, sometimes covered with small excrescences, divided by shallow fissures; inner bark tough, fibrous; bark with a very disagreeable odor when bruised
  • Wood: Pale, greenish yellow, sapwood lighter; light, soft, coarse-grained and spongy with a specific gravity of 0.3969 and a density of 24.74 pounds per cubic foot (396.3 kg/m3)
  • Longevity of fruit production: Undetermined

II. How to Grow and Care

Sunlight

In its natural habitat, the pawpaw tree is found in the understory of forests. As a result, these trees flourish in partial shade. Young trees especially benefit from shady conditions, as bright, direct sunlight can scorch the leaves. Upon maturing, pawpaw trees can be grown in full sun conditions, which is often the case when planted in orchards. These trees will have a more pyramid-like shape, while pawpaws in shade have spreading branches and fewer lower limbs.

Temperature and Humidity

A cold-hardy fruit tree, the paw paw is hardy to USDA zone 5 and can withstand temperatures of -20 degrees Fahrenheit. At the same time, the warm, humid summers of its native habitat provide this tree with the right conditions for growth and fruit production.

You’ll be most successful in growing the paw paw tree if your climate provides the seasonal swing that these trees are accustomed to since the dormancy of winter prepares the tree for a productive growing season.

Watering

Water your Pawpaw enough to maintain consistently moist soil, but not waterlogged. Do not let the soil completely dry out between waterings. Younger trees will need constant watering to thrive. Add a layer of mulch around the base of the tree to help retain moisture. Potted trees will need frequent watering in well-drained soil.

Soil

Soil conditions for the pawpaw must be rich and well-draining. For nutrient-poor soil, add compost to boost soil quality. The pawpaw can grow in heavy, clay soil but only if there is sufficient drainage. Slightly acidic to neutral soil pH levels are best for this tree.

Fertilizing

Pawpaw can be fertilized twice a year in spring and again in summer with a well-balanced solution. Avoid adding fertilizer in the fall to avoid new growth vulnerable to frost. Spread chosen fertilizer around the trunk base of established trees with a rake. Use fertilizer sparingly with younger, more sensitive trees.

Propagation

Pawpaw trees can be propagated by grafting and cuttings. Many nurseries graft scions taken from dormant trees that are at least a few years old. The scions are grafted onto pawpaw rootstock. This method yields good success but is a more advanced method of propagation.

Propagation by cuttings is also possible for paw paw trees but has a high failure rate. It’s not considered the most surefire way to propagate these trees.

Generally, propagation by seed is the most successful way to start pawpaw trees.

Grow from Seed

Growing pawpaw from seed is typically the easiest way to start these trees. A simple route is to plant an entire paw paw fruit in the ground in fall. It will often send up shoots during the next spring season.

But if you want to enjoy the tasty fruit rather than plant it in the ground, you can harvest the seeds from the paw paw fruit and sow them in the ground. Follow these steps to grow paw paw trees from seed:

  • Scoop out the seeds from a ripe paw paw fruit.
  • Next, scarify the seeds. This involves scratching the shell of the seed but not the seed itself. Use sandpaper or a file.
  • In fall, you can directly sow the seeds outside where they’ll naturally stratify over the winter and sprout the following summer. Alternatively, you can stratify the seeds indoors by placing them in a cold location for 90 to 120 days. If you choose indoor stratification, Perdue University recommends placing the seeds inside a plastic bag with moistened sphagnum moss to prevent the growth of mold.
  • Plant seeds once the soil temperature is between 75 and 85 degrees.

Overwintering

Paw paw trees are no stranger to winter weather and the cold season provides a period of dormancy necessary for fruit production in the following year. Since these trees are hardy to -20 degrees Fahrenheit, there is usually no additional care required for successful overwintering mature paw paw trees. There’s no need to water during the tree’s dormancy.

However, a young paw paw tree in a pot should only be planted in spring. To overwinter a young tree successfully, place it in a sheltered location where temperatures will remain above freezing.

Pests and Diseases

Common Pests & Plant Diseases

Relatively hardy and pest-free, the occasional fungal diseases like powdery mildew or black spot may affect paw paw trees that experience high humidity or very damp conditions. In the case of black spot, the fruit is still edible and it’s only an aesthetic issue.

The pawpaw peduncle borer (Talponia plummeriana) occasionally invades trees and causes the blossoms to drop prematurely, affecting fruit yield significantly. In addition, the larvae of Zebra Swallowtail butterflies feed on the leaves of the paw paw tree, but it rarely causes a serious threat to the health of the tree.

Common Problems 

Paw paw trees experience relatively few issues and are hardy enough to grow unattended in the wild. However, when planted in your yard or garden, you may encounter several problems. Moisture management is one of the key problems that growers encounter, since these trees like moist but well-draining conditions. In addition, the paw paw is not a self-pollinating tree and lacks abundant natural pollinators, causing issues with fruit production.

Yellowing leaves

This is a sign of overwatering or poor draining soil. Check the soil to ensure that it’s well-draining. You may need to add compost or peat moss to improve drainage. If overwatering is the problem, withhold water to allow the soil to dry out. Be sure to only water once or twice a week, depending on temperature and humidity conditions.

Lack of fruit production

Even if you have genetically varied trees planted near each other, it can be hard to attract pollinators to paw paw trees. As a result, the flowers may not become pollinated and consequently fail to bear fruit. To solve this problem, one suggestion is to use pollinate paw paw trees by hand. Find the male flowers, which will be wide open and deep maroon color. The stamen will be visible and should be covered with pollen. Place a small plastic bag underneath the bloom and gently tap the back of the blossom to drop pollen into the bag.

Right away, find a female blossom on another paw paw tree. Mature female blossoms will also be maroon, but may still be partly green and will always be only partially open. Gently open the blossom with your fingers enough to reach the paintbrush inside. Then, after dusting the paintbrush with harvested pollen, dab the stigma inside the flower.

III. Uses and Benefits 

  • Edible fruit
  1. triloba is often called wild banana, Indiana banana, or prairie banana because of its banana-like creamy texture and flavor.

The earliest documented mention of pawpaws is in the 1541 report of the Spanish de Soto expedition, who found Native Americans east of the Mississippi River cultivating what some have identified as the pawpaw. The tree’s scientific name (Asimina triloba) comes from the Powhatan word Assimina, which a Jamestown settler transcribed in 1612 as “wheat plum”. The Lewis and Clark Expedition consumed pawpaws during their travels. Thomas Jefferson planted it at Monticello, his plantation in Virginia. Legend has it that chilled pawpaw fruit was a favorite dessert of George Washington.

Historically, the pawpaw was a commonly-eaten fruit throughout its native range. With the advent of motor travel and refrigeration, it has been used less commonly to the point of obscurity in favor of other commercial fruits.

Fresh fruits of the pawpaw are commonly eaten raw, either chilled or at room temperature. However, they can be kept for only 2–3 days at room temperature, or about a week if refrigerated. This short shelf-life and difficulty shipping whole are a primary barrier to the success of pawpaw as a commercial fruit. The easily-bruised pawpaw fruits do not ship well unless frozen. Where pawpaws grow, the fruit pulp is also used locally in baked dessert recipes, with pawpaw substituted with volumetric equivalency in many banana-based recipes. The sweet and creamy fruit is commonly mixed into ice cream or blended into pancakes and other breads.

  • Uses other than food

The tough, fibrous inner bark of the pawpaw has traditionally been used by Native Americans and settlers in the Midwest for making ropes, fishing nets, and mats, and for stringing fish. Because the exotic emerald ash borer beetle is destroying black ash trees (Fraxinus nigra) in its native range, a basketmaker in Michigan whose ancestors traditionally used this northern species of ash has begun planting pawpaw seeds as a potential fiber replacement. The planting is occurring several hundred miles north of pawpaw’s historically native range, so it is an example of assisted migration of a plant in a time of rapid climate change.

Pawpaw logs have been used for split-rail fences in Arkansas. The hard, brown, shiny lima-bean-sized seeds were sometimes carried as pocket pieces in Ohio. Due to the presence of acetogenins, the leaves, twigs, and bark of pawpaw trees can be used to make an organic insecticide.

American Papaw (Asimina triloba) Details

Common name Common Pawpaw, Pawpaw
Botanical name Asimina triloba
Plant type Edible
Hardiness zone 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Medium
Harvest time Fall
Height 15 ft. 0 in. - 30 ft. 0 in.
Width 15 ft. 0 in. - 30 ft. 0 in.
Sunlight Deep shade (Less than 2 hours to no direct sunlight)
Flower color Brown/Copper
Leaf color Green