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Gyrocarpus americanus is a slender, deciduous tree with smooth, grey bark. The tree grows to about 12 m in height. The leaves are spirally arranged, crowded near the ends of the branches, and grow up to 150 × 120 mm in size. They are ovate, often 3-lobed, dark green above, paler and greyer below, with velvety surfaces, 3-veined from the base ...
The seeds, popularly known as "keys" or "helicopter seeds", are a type of fruit known as a samara. Some Fraxinus species are dioecious , having male and female flowers on separate plants but sex in ash is expressed as a continuum between male and female individuals, dominated by unisexual trees.
Male flowers Seeds of Fraxinus excelsior, popularly known as "keys" or "helicopter seeds", are a type of fruit known as a samara. It is a large deciduous tree growing to 12–18 m (39–59 ft) (exceptionally to 43 m or 141 ft) tall with a trunk up to 2 m (6.6 ft) (exceptionally to 3.5 m or 11 ft) diameter, with a tall, narrow crown. [2]
In some cases the seed is in the centre of the wing, as in the elms (genus Ulmus), the hoptree (Ptelea trifoliata), and the bushwillows (genus Combretum). In other cases the seed is on one side, with the wing extending to the other side, making the seed autorotate as it falls, as in the maples (genus Acer) and ash trees (genus Fraxinus). [4]
The distinctive fruits are called samaras, "maple keys", "helicopters", "whirlybirds" or "polynoses". These seeds occur in distinctive pairs each containing one seed enclosed in a "nutlet" attached to a flattened wing of fibrous, papery tissue. They are shaped to spin as they fall and to carry the seeds a considerable distance on the wind.
The good news for the milkvetch plant is that they usually need wildfire to sprout — meaning dormant seeds now have a massive new habitat for a new crop of the rare shrub.
Like all Leucadendrons, this tree is dioecious, with separate male and female plants. The fruit is a heavy woody cone, containing numerous seeds ; each seed is a small nut with a silky-haired helicopter-like parachute, enabling it to disperse by wind.
The advantage of using an airplane/helicopter is the ability to quickly seed large areas, even remote areas, otherwise impractical to be used in active reforestation. Aerial seeding is therefore best suited to sites whose remoteness, ruggedness, inaccessibility, or sparse population make seedling planting difficult.