Promiscuous Grevilleas: There are at least 250 Grevillea species and a huge number of hybrids. Of all the thousands of Australian native plants, the Grevilleas are those that hybridize with reckless abandon. Almost without exception named hybrids have arisen in gardens where a range of grevilleas are cultivated. Grevillea Robyn Gordon is the best-known hybrid and appeared in a Queensland garden and was the result of a liaison between Grevillea banksii a Queensland native and Grevillea bipinnatifida a Western Australian native. This hybrid occurred because the parents were growing in the same garden.
The Poorinda range of hybrids appeared in a Victorian garden over a number of years. A large number of Grevilleas were cultivated in this garden and many hybrid seedlings were grown to maturity. Their horticultural potential was assessed and those with merit were named.
On a personal note: We always have Grevillea seedlings appearing in the gardens at Yallaroo. Because there are now over 100 different Grevilleas growing in the gardens there is a huge number of combinations possible for the production of hybrids. We are always on the lookout for Grevillea seedlings with interesting foliage. Recently we discovered 18 Grevillea seedlings growing in an area of about one square metre. Sugar Ants collected these seeds. These seedlings were potted on and eight were planted in a garden bed. There are four different leaf shapes in this group and two are developing ground covering growth habit. Grevillea seedlings mature in about two years and we are looking forward to their flowers.
There is a downside to this horticultural promiscuity. If your garden is close to natural bushland and you grow a number of different Grevilleas there is the risk of hybrid seedlings invading the bush and becoming environmental weeds.
There are very few naturally occurring hybrid Grevilleas. This is because not many areas have different Grevillea species growing in close proximity. One well-known exception is Grevillea x gaudichaudii. This natural hybrid occurs in the Blue Mountains of NSW. There are reports of other native hybrids occurring in the Grampian Mountains in Victoria.