Propagation
Sow seeds when ripe in situ or in a container and place in an open frame. Germination will occur during spring, prick out and pot up and place outside to harden off.

Note:
Care must be taken when selecting a site as the shallow spreading roots can damage pathways or block drains.

Botanic information
Leaf: The palmately lobed leaves have 3-5 deeply cut lobes with a dentate margins and the reddish petiole is 150mm to 300 mm (12in) long. It is the largest leaf of any maple and is commonly up to 300 mm (12in) wide. The new growth is bronze coloured and pubescent on the underside and during autumn the glossy green leaves turn yellow-orange before falling. 
Note
The rounded leaf buds have overlapping scales.

Flower: The unisexual greenish cup-shaped flowers have 4-sepal-like petals with up to 10-excerted stamens with yellow anthers. The slender pedestal is long and the flowers are arranged in a pendant raceme that is up to 200 mm (8in) long and appears during spring.

Fruit: The large twin samara is reddish when young and matures green with almost glabrous wings at a 60° angle to each other.  The nutlets are densely covered in brown pubescence and the seeds are very viable.

General information on pruning Acer species 
The Maples normally do not require regular pruning apart from damaged, diseased or dead wood removal and this should be carried out from autumn to winter. 

Pruning in late winter or spring may result in bleeding of the sap and should be avoided. Remove reverted branches in variegated trees and clean up split bark with a sharp knife and allow natural healing