The Ginkgo biloba, often called the Maidenhair Tree, is the sole surviving species in its division, making it a living fossil with unique fan-shaped leaves. While many gardeners use cuttings for quicker results, growing this slow-growing specimen from seed is a rewarding, though meticulous, horticultural project. Success requires careful attention to the seed’s preparation and a period of simulated winter. These steps guide you through propagating this ancient tree from seed.
Sourcing and Cleaning the Seed
The journey begins with sourcing viable seeds, found within the fleshy, yellowish ovules dropped by female ginkgo trees in the late fall. These so-called “fruits” are notoriously malodorous, giving off a scent often described as rancid butter. It is imperative to wear thick gloves when handling the ovules, as the pulp contains compounds that can cause contact dermatitis.
The fleshy outer layer, known as the sarcotesta, must be completely removed because it contains germination-inhibiting chemicals that prevent the seed from sprouting prematurely. Clean the ovules by soaking them in water for several days to soften the pulp, then vigorously scrub them to expose the inner, hard, light-colored nut or seed. After cleaning away all residue, rinse the seeds thoroughly with fresh water and allow the hard shell to air dry for several days. Only the fertilized seeds, which will not float when submerged in water, should be kept for planting.
The Crucial Step of Cold Stratification
Ginkgo seeds possess a deep dormancy, meaning the embryo inside is not fully ready to sprout even after the outer pulp is removed. To break this natural inhibition, the seed must undergo cold stratification, a process that mimics the moist, chilling conditions of a winter season.
The standard cold treatment involves placing the cleaned seeds in a plastic bag with a moist, sterile medium such as peat moss, vermiculite, or sand. This medium should be damp but not soaking wet to prevent rot. Store the sealed bag in a refrigerator at a consistent temperature of around 5°C (40°F) for a duration of 60 to 90 days. This sustained period of cold and moisture signals to the seed that winter has passed, priming it for germination once warmer temperatures arrive.
Planting and Germination Setup
Once the cold stratification period is complete, the seeds are ready to be planted in a well-draining growing medium. A mix composed of equal parts peat, perlite, and sand or vermiculite provides the necessary drainage while retaining sufficient moisture. Select a container with good drainage holes and sow the seeds shallowly, covering them with only about 2 to 3 centimeters of the soil mix.
The ideal environment for germination is a protected location with consistent warmth, ideally maintaining a temperature between 20°C and 25°C (68°F–77°F). Keep the planting medium consistently moist but never waterlogged, which is a common cause of fungal issues. Placing the container on a heat mat can help maintain warmth, and covering it with a clear dome or plastic wrap can help retain humidity until the first sprouts emerge, typically within 30 to 60 days.
Nurturing the Young Seedling
After a successful germination, the young ginkgo seedling requires careful attention as it slowly begins its initial growth phase. Ginkgo seedlings typically exhibit a slow growth rate in their first year. The hard seed shell will often remain attached to the sprout for a period, acting as a natural food source for the developing plant.
Once the seedling develops its first true leaves and is large enough to handle, it should be transplanted into its own individual, deep pot to accommodate its developing taproot. Continue to use a highly porous, well-draining soil mix in these new containers. Over the first growing season, maintain consistent moisture and provide bright, indirect light. Before the first winter, gradually acclimate the young tree to outdoor conditions through a process called hardening off, and then protect it in an unheated garage or cold frame before considering its permanent placement.