Plum trees can readily be grown from seed and will develop and mature into a fruit bearing tree in 5-6 years. Harvest plum seeds from very ripe fruit in the summer or early fall, and plant late in the fall or when temperatures drop and the first hard frost has hit your region. The cold set period plus moist, nutrient-rich soil will give the seed a good start. Plant several seeds to increase the odds of successful germination and thin the seedlings later if needed.
Till up at least one square foot of planting area for each seed with a hand trowel to loosen and lighten the ground soil. Remove any rocks or soil clods that you find. Amend the soil with a few pounds of compost and well aged manure if it is not already a very rich, quality humus.
Bury the plum seed roughly 4 inches deep in the soil and cover over it with soil, tamping sown the soil lightly to make good soil to seed contact. Space multiple seeds roughly 12 inches apart as they will be transplanted later. If planting seeds in permanent locations, leave more than 10 feet between seeds.
Water the seed or seeds in well until the surrounding soil is evenly moist. Supplement rainfall with irrigation if the winter season is warm or dry. Moisture works in tandem with the cold weather to crack and germinate the seed so do not let the soil dry out entirely.
Relocate the seedlings only after they are 1 year old or older, which translates to the second spring of a fall planted seed. Water well at transplanting time and never let the sapling root ball dry out.