Cultivating a plum tree from the seed found inside the fruit, known as the pit, is a rewarding project that requires patience. This process bypasses grafting and allows a unique tree to grow from its own root system. Starting a plum tree this way is achievable for the home gardener, though the tree will require several years of nurturing before it matures. The journey begins with careful preparation of the seed to mimic the natural cycle required for germination.
Preparing the Plum Seed
The first step involves extracting the seed from the plum pit and thoroughly cleaning it. After consuming the ripe fruit, the hard pit must be rinsed under cool, running water to remove all traces of fruit flesh and sugary residue. Any remaining sugar can encourage mold or fungus, which compromises the viability of the seed.
Once the pits are clean, they should be allowed to air-dry for a few days on a paper towel. While some gardeners plant the entire pit, success rates are higher if the inner, almond-shaped seed is gently removed from the hard outer shell. A nutcracker or a light tap with a hammer can be used to crack the protective pit without damaging the soft seed inside. Before moving to the next stage, the separated seeds can be checked for viability by placing them in water, discarding any that float.
Simulating Winter: The Stratification Process
Plum seeds possess dormancy, which must be broken before the seed will germinate. Stratification is the process of exposing the seed to prolonged cold, moist conditions to simulate a natural winter, signaling that spring is approaching. Without this cold period, the seed’s germination rate is very low, as chemical inhibitors within the seed remain active.
To perform cold, moist stratification, the cleaned seeds should be placed in a sealed container or plastic bag with a damp medium. Suitable materials include a lightly moistened paper towel, peat moss, or vermiculite, which hold moisture without becoming waterlogged. This sealed environment is then placed in a refrigerator at a consistent temperature, ideally between 36 and 41 degrees Fahrenheit (2–5°C). The required duration for this chilling period is typically 8 to 12 weeks, and the medium should be checked periodically to ensure it remains damp and free of mold.
Sowing the Seed and Early Growth
The transition from the cold stratification environment to the planting stage means the seed is ready to germinate. Once the chilling period is complete, or if a small root has already begun to emerge, the seed can be planted in a suitable container. A small pot, approximately 4 to 6 inches deep, with excellent drainage holes is a good starting choice for planting indoors. Fill the container with a sterile, well-draining seed-starting mix or a blend of potting soil and coarse sand.
Plant the plum seed approximately 1 to 2 inches deep in the prepared soil, covering it lightly and tamping down the surface gently. After planting, the container should be watered thoroughly until moisture begins to drain from the bottom, and then placed in a warm location. Optimal temperatures for germination range from 65 to 75 degrees Fahrenheit (18–24°C), and the soil must be kept consistently moist but not saturated. Germination can occur quickly, often within a few weeks after stratification, but it may take up to a couple of months for the seedling to emerge.
Long-Term Care and Genetic Expectations
Once the seedling has developed its first set of true leaves, it needs a location with ample light to support its growth. Placing the young tree near a sunny window or under a grow light for 12 to 14 hours per day will ensure healthy initial development. As the seedling grows, it will need to be transplanted into progressively larger pots or moved outdoors once the danger of frost has passed. A permanent planting site should offer full sun exposure—at least six to eight hours of direct sunlight daily—and well-drained soil with a pH between 6.0 and 7.0.
A plum grown from seed will not produce fruit identical to the parent plum. Plums are genetically diverse, and the seed contains a unique combination of genes from two parent trees, meaning the resulting fruit will be a distinct hybrid. The tree may produce fruit that is smaller, larger, or has a completely different flavor profile than the original plum, or it may not produce usable fruit at all. Patience is required, as a plum tree grown from seed typically requires 5 to 10 years of growth before it will be mature enough to flower and produce fruit.