Silky oak (Grevillia robusta), which is also known as silver oak, is a tree native to the coastal rainforests of Australia. It has been planted in many parts of the world as a shade tree for coffee and tree plantations. The tree tolerates heavy branch and root pruning, and can be harvested to provide timber, poles, firewood or leaf mulch. The tree's golden-orange blossoms have led it to be considered a decorative ornamental tree. The silky oak is a prolific seeder, producing smooth oval seedpods about 2 cm long (a bit less than an inch) and slightly flattened. Each seedpod contains one or two brown flat seeds about 1 cm by 0.5 cm with shiny centers surrounded by papery wings.
Wait for seedpods to ripen. When they turn from green to yellow and begin to turn brown, they are ready to harvest.
Collect the ripe seedpods by plucking them off by hand or using pruning shears. A pole lopper can be used to harvest seedpods too high to reach by hand.
Line a tray or cookie sheet with paper toweling and spread seedpods out on it in a single layer, so that they do not touch each other. Set the tray in a warm dry spot until the pods open, which should take several days.
Gently separate the seeds from the pods and remove the wings from the seeds by hand. This reduces the chances of fungal infection and will make sowing them easier.
Spread the seeds out on fresh paper toweling and set them out in the sun to dry for a few days. If the weather is cool at night, bring them indoors. If the weather isn't favorable for outdoor drying, keep the seeds in a warm, dry room for up to five days.
Place the seeds in a paper envelope, and put the name of the seeds and the date on the outside of the envelope with a pen.
Place the paper envelope in a plastic food storage bag and store in a cool, dry, dark location until it's time to plant the seeds.