Japanese maples (Acer palmatum) are small, deciduous trees cherished worldwide for their delicate foliage and vibrant seasonal color changes. These ornamental trees are popular in landscaping and garden design, but they also produce a distinctive fruit containing their seeds. Understanding the appearance and life cycle of these seeds is helpful for both identifying the tree and for those interested in propagation. The unique structure of the Japanese maple seed is an adaptation that aids in its dispersal.
Anatomy of the Samara
The fruit of the Japanese maple is not a simple seed but a winged structure called a samara, characteristic of all maple species. Japanese maples produce a type of fruit known as a schizocarp, where two individual samaras remain joined together until they dry and separate (often called a diplosamara). Each paired samara consists of a papery wing attached to a small, hard casing at the base, which holds the actual seed.
The overall length of a single samara, from the tip of the wing to the seed case, ranges from about one-half to just over one inch long. When they first form in early summer, these paired fruits are often a vibrant green or a noticeable reddish-burgundy color. As the fruit matures, the wings become dry and papery, transitioning to a light tan or brown color. The two wings are often angled, sometimes forming an incurved arch, which helps them spin like a miniature helicopter as they fall.
The seed itself, or the nutlet, is small and rounded, encased within the hard, protective shell at the base of the wing, which shields the embryo inside. The appearance of the seed case is a key difference from other maple varieties, which can have varying sizes and angles of their paired wings. The samara’s lightweight structure catches the wind, allowing the seed to travel some distance from the parent tree before landing.
Seasonal Timing and Ripening
Japanese maple trees begin their reproductive cycle in the spring, from April to June, when they produce small, often reddish-purple flowers. Following pollination, the samaras develop and remain on the tree throughout the summer months. During this period, the fruit is soft and colorful, actively maturing the seed embryo inside.
The ripening process concludes in the fall, spanning from September to October, depending on the local climate and specific cultivar. Ripeness is signaled by a distinct visual change as the fleshy green or red color fades and the samara becomes dry, brittle, and brown. Once the seeds are fully mature, they begin to drop naturally, often coinciding with the shedding of the tree’s leaves. It is during this late autumn window that the seeds are viable and ready for collection.
Collecting and Germinating Seeds
The best time to collect the seeds for propagation is when they have reached the dry, brown stage and are just beginning to fall from the tree. The first step is to prepare the seeds for planting by removing the papery wings, a process commonly called de-winging. Following this, the hard seed cases should be soaked in warm, but not boiling, water for 24 to 48 hours to help soften the tough outer shell.
A necessary step for successful germination is stratification, which mimics the natural cold and moist conditions of winter required to break the seed’s dormancy. This is achieved by mixing the seeds with a moist, sterile medium, such as peat moss or sand, and placing them in a sealed plastic bag. The bag is then refrigerated at a cool temperature, ideally between 38 and 50 degrees Fahrenheit, for a period of 90 to 120 days.
Once the chilling period is complete, the seeds can be planted in a pot or prepared seedbed, covering the nutlet with only a shallow layer of soil. The stratification process ensures that the embryo is ready to sprout when the warmer temperatures of spring arrive. Growing Japanese maples from seed is a patient process, but it is a rewarding way to propagate these trees.