The familiar “helicopter seeds,” formally known as samaras, are winged seeds that twirl to the ground in spring and summer. Their unique design allows them to travel beyond the immediate vicinity of their parent tree. This article explores which trees produce these distinct seeds and the science behind their aerial journey.
Common Trees with Helicopter Seeds
Maple trees (Acer species) are the most recognized producers of helicopter seeds. Their samaras feature two conjoined wings, forming a V-shape, with a seed located in each wing. Common varieties like Sugar Maple, Red Maple, Silver Maple, and Norway Maple all produce these paired samaras. Red Maple samaras can emerge with a reddish color, while Norway Maple samaras are larger, measuring approximately 10–15mm wide with wings 30–50mm long.
Ash trees (Fraxinus species) also produce samaras, though their design differs from maples. Ash seeds are single-winged and paddle-shaped, measuring about 25-45mm long with a width of 5-8mm. These single-winged samaras hang in bunches on the tree and are sometimes called “keys”. Ash trees are medium to large deciduous trees, often identified by their compound leaves with 5-11 leaflets and bark that develops diamond-shaped ridges as it matures.
Box Elder trees (Acer negundo) also produce winged seeds. Although often recognized separately, Box Elders are technically a type of maple tree. Their samaras are V-shaped and hang in clusters, similar to other maples. These trees are known for their adaptability and ability to thrive in various environments.
The Science of Winged Seeds
The spinning descent of samaras results from aerodynamic principles. When these winged seeds fall from a tree, their unique shape causes them to autorotate, like a helicopter rotor. This autorotation generates lift, which slows the seed’s descent and keeps it airborne longer. The wing’s design, including its curved upper surface and flat lower surface, creates a pressure difference that generates this lift.
This spinning flight aids seed dispersal. By staying airborne longer, the samaras can be carried further from the parent tree by wind currents. This increased dispersal distance reduces competition for resources between the new seedling and the established parent tree. It also increases the likelihood of the seed landing in a suitable location for germination, promoting the spread and genetic diversity of the species.
Wind plays a significant role in this dispersal mechanism. Even a light breeze can carry spinning samaras a considerable distance from the original tree. The ability of these seeds to shed raindrops quickly also helps them maintain their flight in various weather conditions. The strategic distribution of mass within the seed and wing also influences its flight behavior, contributing to efficient wind dispersal.
Beyond the Maple: Other Trees with Similar Seeds
While maples are known for their helicopter-like seeds, other trees also produce winged seeds with different dispersal characteristics. Elm trees (Ulmus species) are one example, producing samaras that are round and disc-like with a single seed within a papery casing. Unlike the distinct spinning motion of maples, elm samaras tend to flutter as they fall. Elm trees are common shade trees, identified by their serrated, oval leaves and often vase-shaped crown.
The Tree of Heaven (Ailanthus altissima) also produces winged seeds. Its samaras are single-winged, somewhat twisted, and can be green with a rosy tinge, turning brown as they mature. These seeds grow in large, drooping clusters and are dispersed by wind. The Tree of Heaven is a fast-growing deciduous tree, recognized by its large compound leaves and smooth, light gray bark.