Ginkgo biloba produces neither seeds nor fruit. Male trees bear pollen and female trees, ovules, commonly called “fruit.”
A mature ovule resembles a small golden plum. Beneath the fleshy outer layer there is a woody shell that looks like a large pistachio. This “seed” contains an almond-like “nut” (see the box below).
Gather the ovules when they fall to the ground in late October or early November. It is important to wear gloves when handling the ovules, because contact with the fleshy layer can cause dermatitis. This “pulp” is also toxic if ingested. Note that the pulp gives off an odour of rancid butter or vomit as it decays.
Soak the ovules in water to remove the fleshy layer. To allow the embryo to completely mature, you will need to warm stratify the “nuts” for 6 to 8 weeks, and then cold stratify them for the same length of time or even all winter. After this artificial stratification period, you can pot them up. The containers can be placed outdoors once temperatures are warm enough in spring. Alternatively, you can sow your ginkgo “nuts” in the fall directly in the ground or in containers buried in the soil, to stratify them naturally. Only fertilized ovules will germinate.
Artificial stratification is intended to reproduce the natural conditions the seeds need in order to germinate. An easy way to stratify ginkgo “nuts” artificially is to mix them with moist sand, vermiculite or peat moss in clear plastic bags with small holes punched in the sides. For warm stratification, keep the bag at 20 to 30°C. Check the medium periodically to make sure that it doesn’t dry out. A refrigerator (at about 5°C) is ideal for cold stratification.
An almond or pit is the seed of a peach, plum, apricot and other drupe or stone fruit. A ginkgo “almond” or “nut” is actually the endosperm or female prothallium (nutrient-storage tissue). It is eaten in Asia, despite being potentially toxic. Cooking is said to destroy the toxin (ginkgotoxin), but the cooked “nuts” should still be eaten in moderation. A number of cases of poisoning have been reported, with children being most vulnerable.