The Ginkgo biloba tree represents a lineage that extends back over 290 million years, earning it the title of a “living fossil.” This ancient species is the sole survivor of its entire division of plants. Its distinctive fan-shaped leaves have a unique two-lobed structure, contributing to its scientific name, and turn a brilliant golden yellow in the autumn. The tree’s remarkable durability allows it to thrive in urban settings, where it is valued for its unique appearance and ability to withstand pollution.
Addressing the “Bloom” Misconception
The idea of a ginkgo tree producing a “bloom” is a common misconception because it is not a true flowering plant. As a gymnosperm, the ginkgo does not produce the showy flowers characteristic of angiosperms, which are plants with enclosed seeds. Instead of traditional flowers, male and female ginkgo trees develop small, inconspicuous reproductive structures. This species is dioecious, meaning individual trees are either exclusively male or exclusively female, so a single tree cannot reproduce on its own.
Male trees produce small, yellowish pollen cones that are loose, catkin-like structures. These pollen cones appear clustered on short spur shoots and are designed to release pollen grains into the wind. Female trees produce two or sometimes three ovules at the end of a stalk, which are also found on the short spur branches. These ovuliferous structures are the precursors to the seeds but do not resemble a conventional flower.
Seasonal Timing of Pollination and Seed Production
Reproduction begins early in the spring, typically around March or April, when the male trees shed their pollen. The wind carries this pollen to the receptive ovules on the female trees, a process known as wind pollination. The male catkins emerge just before the leaves unfurl and quickly fall off after releasing their pollen.
After pollination, the female reproductive cycle involves a significant time delay before fertilization occurs. Fertilization does not take place immediately, but is delayed until late summer or early fall, around September or October. This long gap between pollination and fertilization means the entire reproductive cycle, culminating in a fully developed embryo, can take approximately 14 months.
The seeds begin to develop on the tree and drop in the fall, typically in September or October. These seed structures resemble small yellowish plums, consisting of a hard inner shell surrounded by a soft, fleshy outer layer. This outer layer, called the sarcotesta, contains butyric acid, which is responsible for the characteristic foul odor often compared to rancid butter. The embryo continues to develop even after the seed has fallen from the tree.
Age Requirements for Reproductive Maturity
Ginkgo trees have an extensive juvenile period, meaning they must grow for many years before they are capable of reproduction. A ginkgo tree typically does not reach sexual maturity until it is between 20 and 40 years old. This long span of time without reproductive structures makes it nearly impossible to determine the sex of a young tree by visual inspection alone.
Only once this maturity is reached will a tree produce the pollen cones or ovules that initiate the reproductive cycle. The nursery trade often addresses this delay and the unpleasant seed odor by cultivating male cultivars, which are clones grafted from mature male trees. Planting these known male trees ensures the absence of the malodorous, seed-bearing structures.