Asimina triloba is a deciduous under-branch small tree or bush. The tree itself is not demanding and grows rapidly in a variety of soil conditions, optimally in moderately acidic soil of pH 5.5-6.5. The plant is however sensitive to strong full sun and must be shaded for the first two years. Without shade the leaves will get burned and may fall off and that will lead to slower growth of Asimina.
Nurseries will usually carry 2 years or more old saplings that can be transplanted easily. Care must be taken when transplanting to avoid damaging the long tap root that Asimina has. Damaging the tap root will hinder growth rates significantly and could even result in plant death. When transplanting it is usually best to try to keep the soil around the roots undisturbed.
It is also good to frequently water the plant during dry season until root system develops fully. After 2 years watering is not needed except perhaps in severe drought..
If the tree is grown from seed it may take up to 6 years to see first fruit production. Grafted Asimina triloba will produce fruit in about 2 years after transplanting.
Each fruit of Asimina triloba contains 8-12 larger seeds. The seeds are brown to dark brown colored, but will turn light brown when dried. Asimina seeds should not be allowed to dry as this will severely reduce the vitality of the seed. If dry seeds are exposed to "higher" temperatures its vitality will drop down to zero. Seeds are 15-25 mm in length. After the fruit has been consumed the seeds should be thoroughly washed to remove the pulp residue. This will help to reduce mold problems.
Asimina triloba seeds need to be stratified before seeding. When removed from the fruit the seeds are in a dormant state and if seeded will not sprout. They need to be exposed to winter conditions first. This is best accomplished by placing the seeds in a plastic bag together with some soil or peat moss, moistened and stored in the fridge at 4-8°C for at least 2 months. An enzymatic reaction will occur in the seeds at low temperatures and awaken the seed. This process is called stratification. Ziploc plastic bag will work nicely. Seeds should never be allowed to freeze as this will damage the sleeping embryo often killing the seed completely.
After the stratification process is complete the seeds are transferred in to a plastic box with a lid. About 10 cm of humus rich substrate is added to the box, seeds are seeded into the soil and the soil is moistened and covered to help prevent evaporation. The cover should not be to tight and allow for some air penetration. The plastic box should be placed in an environment with a temperature above 20°C. Asimina triloba seeds will sprout best at 29°C. The seeds in the soil should be checked regularly and moistened to prevent the developing seed from drying out. Germination process takes a long time for Asimina and in optimal conditions the seeds will start to sprout after 3 weeks, but in less than optimal conditions seeds will start sprouting after 5 weeks or more.
Less then 4 weeks after planting the seeds first roots can be observed. The roots are 1-6 cm in length. It is much easier to transplant seeds with a short root as it is less likely for the root to get damaged during transplantation. Rooting seeds are transferred to individual 40cm tall planting pots.
Seeds that show signs of life should be planted to tall planting pots as soon as possible. If tall planting pots are not available the roots will not have enough depth to develop properly. Due to unavailability of deep planting pots I used two 20 cm pots and taped them together, to make a 40cm deep planting pot.
Seeds should be planted about 1 cm deep and care should be taken to keep the substrate moist. The root should never dry out completely. Water as needed but do not allow the substrate to completely dry out. It is also not a good idea to water too much.
In a couple of days the young shoot will straighten up. Once the shoots appear out of the substrate light should be applied as soon as possible to prevent the shoot overstretching as this would result in long but weak shoots. As soon as light is applied first leaves will develop rapidly. Fluorescent lighting or partially shaded natural sunlight will work nicely.
About 4 months after planting the seeds this Asimina is about 40 cm tall and has 9 leaves. The plant is watered when the substrate is almost dry. Do not over-irrigate at this point as the stem could develop rot and the plant might fail.
If the tree is kept indoors enough light should be applied to avoid overstretching.