Some plants are grown purely for their foliage, and Grevillea robusta, the Silk Oak or Silk Bark Oak, is one of them. The finely cut, fern-like leaves of this Australian plant, silvery-bronze in colour, make it attractive for greenhouse decoration. When stood between begonias, gloxinias, primulas and similar plants they set theoff admirably.
In addition to its usefulness as a greenhouse plant, G. robusta is used for summer bedding and window-box decoration.
Cool, airy conditions suit this plant best; indeed the leaves tend to drop if the air is hot and stuffy. It is quite happy with a temperature of 4°C. (40°F.) during the winter months. Rapid growth is made in summer and water is needed in some quantity.
This plant is increased by sowing seed in a propagating frame between April and September. A temperature of 16°C. (60°F.) is needed for successful germination. It should be noted that the seed can sometimes take many months to germinate.
When the seedlings have developed their second pair of leaves, they should be potted separately in 3-½-in. pots using John Innes No. 1 or 2 Potting Compost. When the root system has permeated the compost, pot on into 5-in. and subsequently into 7-in. pots. When these have been outgrown the plants are too large for the greenhouse and should be discarded. I sow seed each spring to maintain a regular supply of young plants for growing on.