How To Plant Pawpaw Tree Seeds: Tips For Germinating Pawpaw Seeds
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Once a common understory tree native to the eastern United States, pawpaw trees have become increasingly popular in the landscape lately. Not only do pawpaw trees produce delicious fruit, but they also make attractive small, low maintenance trees for the landscape. In organic gardening, they are popular due to their resistance to pests and diseases, fitting in perfectly with chemical-free garden practices. With the many dark brown seeds produced in each pawpaw fruit, gardeners may naturally wonder: Can you grow a pawpaw tree from seed?
Can You Grow a Pawpaw Tree from Seed?
If you are seeking instant gratification and hoping to immediately enjoy its fruits, then purchasing a growing rootstock cloned pawpaw tree may be the best option for you. When growing pawpaw trees from seed, the more pertinent question is when to sow pawpaw seeds, rather than how to plant pawpaw tree seeds.
Most gardeners have heard the old Chinese proverb, “The best time to plant a tree was 20 years ago.” While 20 years may be a little excessive, many fruit trees, pawpaw included, do not bear any fruit for many years. When planted from seed, pawpaw trees usually do not produce their fruits for five to eight years.
Growing pawpaws from seed is an exercise in patience, as the seeds are slow to germinate and require special care. In the wild, pawpaw trees naturally grow as understory trees. This is because germinating seeds and young seedlings of pawpaw are extremely sensitive, and even killed by direct sunlight. To successfully grow pawpaws from seed, you will need to provide them with some shade for the first year or two.
How to Plant Pawpaw Seeds
Even when provided with adequate shade, germinating pawpaw seeds requires a 60- to 100-day period of cold, moist stratification. Seeds are generally sown directly in the ground, or in deep tree containers in late fall, after the seeds ripen in fall. Stratification can also be mimicked in a refrigerator at 32-40 F. (0-4 C.). For this method, pawpaw seeds should be placed in a Ziploc bag with moist, but not wet, sphagnum moss and sealed.
Seeds should be kept in the refrigerator for 70-100 days. Once removed from the refrigerator, the seeds can be soaked in warm water for 24 hours to break dormancy, then planted in the ground or in deep containers. Pawpaw seedlings usually sprout a month or two after germination but aerial growth will be very slow for the first two years as the plant expends most of its energy in to root development.
Pawpaw trees are hardy in U.S. hardiness zones 5-8. They prefer well-draining, slightly acidic soil in the pH range of 5.5-7. In heavy clay, or waterlogged soils, pawpaw seedlings will not perform well and may die. Proper drainage is essential for optimal growth. Pawpaw trees also do not transplant well, so it is important to plant pawpaw seeds in a site where they can permanently stay, or in a large enough container where they can grow for some time.
Pawpaw seeds, like their fruit, have a very short shelf life. Seeds should never be stored by drying or freezing. In just three days of drying, pawpaw seeds can lose about 20% of their viability. Pawpaw seeds ripen in fall (September to October), and are usually removed from the fruit, washed and used immediately for seed propagation.
When planted in autumn, pawpaw seeds usually germinate and produce shoots in summer of the following year.
How to Sprout Wild Paw Paw Seeds
Sometimes called custard apples, pawpaws (Asimina triloba) occur naturally within the hardwood forests of the southeastern United States. Gardeners within U.S. Department of Agriculture plant hardiness zones 5 to 9 can grow pawpaws with few problems, although they require partial shade when young and fast-draining soil to truly thrive. Seed propagation is the most effective method for growing pawpaws, and they will sprout reliably in just a few months. However, to ensure successful germination, wild pawpaw seeds must be potted in soil from the parent tree's growing site to inoculate the seedling with the proper soil microbes.
Gather the seeds from a ripe pawpaw fruit in autumn once the skin is solid light-green and the flesh yields to slight pressure. Slice the fruit in half, and pop out the dark brown, bean-shaped seeds with a spoon or the tip of your knife.
Place the seeds in a colander, and run water over them until all of the creamy, sticky fruit pulp has washed away. Dry the seeds on a dishcloth or paper towel.
Store the pawpaw seeds inside a paper bag away from heat and humidity until late winter, approximately two months before the last frost. Inspect the seeds, and discard any that appear damaged or rotten.
Put 2 cups of moistened sphagnum moss into a plastic freezer bag. Nestle the pawpaw seeds into the sphagnum moss so they are completely surrounded by the moist medium. Close the bag.
Store the bag in the vegetable drawer of a refrigerator for two to four months to cold stratify the pawpaw seeds. Mist the sphagnum whenever it feels slightly dried out.
Prepare a planter for each pawpaw seed after the chilling period has ended. Fill 2-gallon nursery containers with a mix of standard potting soil and 3 to 4 tablespoons of soil taken from the parent tree's growing site.
Poke a 3/4-inch-deep hole in the soil mixture. Place the pawpaw seed in the hole lengthwise. Bury it with loose soil. Pour water into each pot to distribute the beneficial microbes from the growing-site soil throughout the mix.
Place the potted pawpaw seed indoors near a window, or outdoors in a cold frame or on a lightly shaded porch. Choose a spot with at least six hours of direct sunlight daily.
Set the pots on a propagation mat to promote faster germination if daytime temperatures are well below 70 degrees F. Set the temperature to between 70 and 85 degrees F. Do not lower the temperature at night.
Check the soil moisture level daily to ensure the top inch stays moist at all times. Drizzle water onto the soil whenever the surface dries out. Add water until the top 1/2 inch feels fairly saturated.
Watch for a single stem sprout in midsummer approximately two months after sowing. Transplant the pawpaw seedling into a bed with full or partial sun and moist, acidic soil. Space multiple trees at least 15 feet apart.
Pawpaw Reference Table
|Common Name||Pawpaw Tree, Appalachian Banana|
|Native Range||Eastern United States, USDA Zone 5-9|
|Scientific Name||Asimina triloba|
|Height / Spacing||15-30′ (5 m – 10 m) / 10-20′ (5 – 10 m)|
|Light Conditions||Full Sun to Full Shade|
|Soil Type||Sandy, Loam, Humus|
|Moisture||Wet to medium – not drought tolerant|
|Harvest Time||Late Summer, Autumn|
How to establish your Pawpaw plants
To successfully grow pawpaw fruit we must first understand a few things about its natural history. The tree grows primarily in river floodplains and shady rich bottomlands. They form dense groves, spreading clonally by underground runners and spend many years growing as an understory species until there is a break in the canopy and they can make their leap into the sunnier conditions provided by an opening in the canopy. It is only once they are growing in fuller sunlight that they produce significant crops of their delicious fruit. These are the conditions we must try to mimic in order to grow healthy paw paw trees that give us good crops.
Rich, deep, well draining soils are ideal conditions for planting your new pawpaws in. Although they grow in river floodplains that may become seasonally inundated, the pawpaw does best when it has deep well-drained soil with a pH between 5.5 and 7.0. To mimic the understory conditions that the pawpaw needs for its establishment years you could plant on the north side of a fence where the pawpaw will be shaded while its young but receive full sunlight as it matures and grows above the fence line.
Another option is to establish a quick growing nitrogen fixing tree or shrub on the south side of where you plan on planting your pawpaw. Get this tree established the year before so it can provide adequate shade for your newly planted pawpaw tree. Choosing nitrogen-fixing species gives you a quick growing tree that will properly shade your pawpaw as well as providing fertility for the tree. The shade tree can then be cut down a few years later once your paw paw is established and the danger of sunburnt leaves and shoots is no longer a threat.
A third option is to plant quick growing annual legumes on the south side of the pawpaw while also building a simple bean or pea trellis over the top of the paw paw to provide quick shade, nitrogen fixation, as well as a crop from your leguminous shade-giving plants as you wait for your pawpaws to mature. Also, planting in a site that is as humid as possible is ideal for the pawpaw. Near a pond can be a great place to plant if you are in an area with dryer summers like we have here in the Pacific Northwest.
The paw paw can be a very difficult species to transplant. It has a very deep root system and does not like its roots to be disturbed or broken. For this reason we sell pawpaws while they are still quite small to ensure higher transplant success rates. While the plant is dormant, or in the spring just after bud break, is the best time to transplant. Be very careful not to disturb the roots. Water in well just as you would any other tree and keep very well watered for the first couple years.
Pawpaws can be spaced relatively close together, even as close as 5 feet. Because you will most likely be planting grafted named cultivars, this is the best way to mimic the dense root suckering groves that paw paws form in the wild. It’s believed that pawpaws actively graft their roots together and share nutrients. More readily than many other species and close plant spacing helps to achieve this. Planting as close as 5 feet or as far as 10 feet apart, and planting at least three different varieties for cross-pollination, has been shown to be the most successful.
Pollination can be the major limiting factor to getting good crops of pawpaw fruit. The flowers are protogynous meaning that the female organ, the stigma, ripens before the pollen does and is therefore not receptive when the pollen is ripe. This ensures that the flower cannot pollinate itself. The entire tree is also usually self-incompatible, meaning that pollen from one flower on the tree will not pollinate the stigma of other flowers on the same tree.
Therefore the pawpaw requires pollination from a tree with entirely different genetics to be successfully pollinated. This is why we always suggest purchasing many different paw paw varieties to ensure the most successful pollination. The more trees you have the more successful your pollination will be. Two varieties is the absolute minimum you can plant to get fruit but more fruit is produced with three or more varieties.
Finally, you must attract the pawpaws natural pollinators to achieve successful transfer of the pollen between flowers. In this case keeping honeybees will not help you out as the pawpaw flowers are designed for the decomposers of the world. They are a deep and beautiful reddish purple color and smell a bit like rotting flesh in order to attract various species of flies and beetles. One strategy for attracting these pollinators is to put road kill or rotting meat near your pawpaws when they are flowering to attract their natural pollinators. If this sounds too unappealing to you it is also possible to pollinate by hand, just be sure that once the tree starts setting fruit that no single branch is too loaded up with fruit or it may cause it to break or result in smaller fruits.
Pests and Diseases
The pawpaw is relatively pest and disease free. If you have deer problems in your area then pawpaw trees are a wonderful choice. Deer avoid eating pawpaw leaves even in areas where deer populations are sky high. A few insect pests exist, but most are relatively minor.
The pawpaw peduncle borer (Talponia plummeriana) burrows into the flowers causing them to wither and drop and can even destroy the majority of blossoms, although this is rare. Other pests in the Eastern United States include the Zebra Swallowtail Butterfly (Eurytides marcellus) whose larvae feed exclusively on young pawpaw leaves. The relationship between the Zebra Swallowtail and the pawpaw is similar to that of the Monarch butterfly and the milkweed plant.
The acetogenins that are present in the paw paw leaves remain present in trace amounts in the Zebra Swallowtails body for the remainder of its life, making it unpalatable to birds or other predators. The incredible beauty of the Zebra Swallowtail and the minimal damage it does to the leaves make this insect not much of a concern. A blue stain disease can also infect paw paws but it is not believed that a microbial agent is responsible for this but rather it is a result of stress or trauma to the tree. In general pawpaws are one of the most disease and pest resistant fruit trees that you can grow.
The best way to select your varieties is to contact your local agricultural extension agency and ask them which pawpaw varieties will grow best in your area. In general, we recommend the earlier fruiting varieties for areas where summers are not as humid as the eastern United States where the pawpaw is native.
Using the Pawpaw Fruit
The fruit is primarily used for fresh eating. It is extremely perishable and is amazingly delicious when it is perfectly ripe. It can be used much like you would use a banana. Try replacing bananas with paw paw fruit in a banana bread recipe or adding paw paws to a berry smoothie. For longer-term storage you can freeze the fruit and make ice cream out of it. Any recipe that requires adding heat or cooking the pawpaw is not recommended as the flavor compounds are extremely volatile and cooking can destroy the delicious pawpaw flavor, although it seems to retain a good flavor when mixed with flour and used as a baking additive.
Let us know about your experiences with paw paws, which varieties work best in your area, what recipes you’ve found to use them in, and what strategies have been successful for getting them established, and enjoy the look and taste of this amazing tropical tree in your own backyard!