How to grow Pawpaw from seed•
Posted on October 26 2022
How to grow Pawpaw from seed
Pawpaw is a unique, uncommon, and lovely autumn fruit that everyone should try at least once. The trees are an understory shade plant, with a floppy–leafed canopy, slow–growing and deciduous. The trees can be found along creeks and in valleys throughout the eastern USA, and luckily for us, pawpaw is also native to southern Ontario and Quebec. With what tastes like a tropical fruit, pawpaw seems almost out of place as far north as Canada. If you want to read up on common pawpaw visit this blog to learn the basics about this wild fruit!
To process seeds, slice the pawpaw fruit lengthwise and remove the seeds. You will notice a membrane surrounding each seed that attaches its base. You can peel this away or leave it attached, but leaving the membrane intact will lead to mould growth in the storage/stratification stage. The mold will not harm the seeds but may be off-putting to work with. Using a knife, separate the membrane and pop out the seed, then place it in a damp paper towel or your prefered substrate.
Planting pawpaw requires that seeds be stratified for 80 to 120 days. We store our seeds in a sealed ziplock bag with damp paper towel in the fridge from October until February. Alternatively, you could place seeds in a moist lidded tray filled with sand and vermiculite. Starting seeds in February inside gives the trees ample time to germinate before spring and extends their first growing season. It is important that seeds remain moist and at no point are left to dry out before being stored or germinated. Seeds that have been frozen may germinate, however freezing can significantly reduce the amount of viable seeds.
In February, when the seeds have been removed from stratification, lightly score them along their seam and, leaving them in or moving them to a lidded tray, cover lightly with a sand and vermiculite mix, triple mix, or potting soil. If your seeds are moldy give them a rinse; the mold will not harm them. The pawpaw seeds will begin to germinate at around 16°C ( 60.8°F ) after about three weeks. However, the unpredictable nature of germination means that three weeks could stretch to three months. Don't get discouraged if they don't show signs of life in March or April. Roots will eventually emerge!
Planting temporary pots
When your pawpaw seeds have begun to sprout, plant them just below the surface of loosely packed tall pots, 10 inches deep minimum. ( One litre milk cartons with holes punched in the bottom work okay .) We use tree pots imported from the US that are open at the base and will allow the roots to protrude from the bottom. I've seen people use stapled, cut up yoga mats and poster tubes cut into 12-in lengths. The seed will shoot down a long tap root before it does much above the soil. You want to give the tap root plenty of room to avoid growing into a J-root and causing issues such as stunted growth or sudden loss of the tree later on.
While fruit trees can really be planted whenever you can work the soil, to give your pawpaws their best start, plant them either in early spring, before you see any leaves forming, or in mid fall when trees start to change colour and lose their leaves. This will reduce stress on the trees as any leaf that starts off in sheltered or greenhouse conditions will not be as tolerant of the sun as a leaf that grew in sunny conditions. If you start your seeds in February inside, your first-year growth will not be accustomed to the sun. You will want to keep them shaded or behind glass for the first year and plant them any time after mid September to early November. This autumn planting will give them time before they go dormant to shoot down roots while they lose their leaves, avoiding the brightest and heaviest sunny conditions of summer that can scorch them.
Your pawpaw's forever home
Now that you have a sprouted pawpaw growing happily in a tree pot or milk carton, you will want to find a forever location for your tree, either before it goes dormant after its first year of growth or in the early spring while it is still dormant. Because pawpaws put down deep tap roots, replanting them is difficult and could cause permanent damage to the trees. So wherever you put them should be suitable for them to live permanently. Keeping in mind that the tap root drives growth, planting them in super rocky soil and places where they would compete with other tree roots will slow or hamper their growth rate. Find a location with rich slightly acidic soil that has good drainage and few other plants competing for resources.
How to plant
How you plant pawpaw can have a significant effect on how quickly they grow. While factors such as genetics and soil conditions will dictate growth rates to an extent, some simple procedures can really help start them off on the right track. Dig twice as deep as you need to accommodate the tap root. This will let you know if there are any obstructions under the tree that might interfere with growth. It will also loosen the soil, making it easier for the roots to grow downward. A small handful of blood meal or bone meal can help stimulate root growth and give the tree a little boost, the addition of chemical fertilizers may stunt growth or burn the young trees, so keep it simple.
After planting, surround the pawpaw with mulch, making sure not to pile it up around the stem or trunk of the tree, as that can lead to mold and pest issues. If you are planting trees in spring and or summer that are already in leaf, some shade cloth may come in handy as trees that are not accustomed to direct sun may scorch. If the trees are already habituated to sunny conditions, the shade cloth is optional. Many people advise you give the trees some shade during their first few years of growth, however it is possible to growth them in full sun, as long as they get ample water.
Pawpaws don't need special attention when it comes to winterizing them, but young trees can always benefit from mulch, raised shade cloth and deer fencing; however wrapping trees in burlap may result in rodent damage, so it's not advised. Pawpaw is hardy in zones 6 and 7 and they can survive in zones as cold as 5a or 5b and perhaps even 4. There are fruiting pawpaw trees as far north as Ottawa, Ontario, and it is entirely possible that global warming will extend their habitable range farther. Pawpaw trees can generally resist colds down to -30°C or -22°F.
Organic milk-based paint applied to the south-facing side of a small tree can help prevent trees from cracking in the winter sun. As the sun warms the tree trunk, it can cause sap to flow out of season, resulting in cracks and breaks in the bark that can lead to stress that will later affect the health of the tree and the amount of fruit it produces. If your plants are already shaded from winter sun, this is less of an issue.
The best way to get your hands on some seeds is to find ripe pawpaws. There are also a few places online that will have them, or you can always ask us at Forbes Wild Foods shortly after pawpaw season if we have any fruit left. While not true-to-parent, pawpaws will have many of the same features of their parent trees; fruit flavour, size and hardiness may all be passed down, so there is a good chance that if you enjoyed the fruit you got your seeds from, your trees will produce the same wonderful pawpaw fruit themselves.
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