Sugar maple trees seldom flower until they are at least 22 years old, and flowering is heavier at later ages.
Typically, both male and female flowers are produced on the same tree.
Maple trees are considered to be wind-pollinated. Flying insects may also play a role in pollination.
The production of seed begins with pendulous clusters of yellowish flowers that appear over the entire crown of mature sugar maple trees in late April to early May, depending on geographic location. This timing is usually just before leaves start to develop.
Sugar maple flower Photo credit – bobklips.com/bob
The fruit, a double samara, ripens in about 16 weeks changing from a dark green colour to yellow-brown at maturity. Only one of the paired samaras will form a viable seed. The seed is collected in late September either by spreading tarps under the trees to collect the seed as it falls or by collecting it directly from the trees by hand using ladders.
Seed can be stored for several years, if properly conditioned prior to storage and monitored during the storage period. Some nurseries will store sugar maple seed when a heavy seed crop occurs perhaps anticipating a poor crop the following year. The potential to germinate declines as the storage period extends.
Most nurseries prefer to sow sugar maple seed in the fall covering the beds with a mulch. Stratified seed can be sown in the spring, but results are variable and frequently disappointing.
Sugar maple seedlings are large enough to plant as two- or three-year-old seedlings, occasionally as a larger transplant. Seedlings are selected and lined out in fields for an additional 3-4 years before becoming the 4-6 foot tall saplings planted by many of MLF’s Customers.