Growing a Grevillea is not a tough proposition but try to propagate them and you’ll quickly understand what a challenge this plant can be – especially for the home gardener. It’s not that they require such special treatment but the success rate can be quite low and even in commercial settings there is still much that is being learned about these plants. The methods that work for one species does not naturally translate to another.
This can be extremely frustrating or the challenge that you were looking for. Grevillea propagation is not a defined science yet and while there are ways that are proving to be successful experts are still be bamboozled by this species.
At present, there are three main ways to propagate grevillea: grafting, cuttings and seed germination.
Grafting has proven to be the most successful propagation technique by using Grevillea robusta as the rootstock. While this won’t work for every grevillea variety it is successful for most. Plus, G.robusta is one variety that grows well from seed propagation.
Cuttings are another option that have a fairly good strike rate. Semi-hardwood cuttings taken at the end of autumn are going to be the most beneficial material. You will need a cutting of around 100mm (4ins) in length. Once you have your grevillea cutting, remove the lower foliage and strip back some of the bark on the stem to expose the living tissue. Then dip this into some very strong root hormone powder or gel – I would recommend the gel – and then place into trays, or pots, of potting mix.
Your cuttings should strike within a few months and hopefully go onto grow into a healthy specimen. If they don’t seem to be doing too well then remove them from the potting medium, scrape the stem back again and re-dip into the footing gel and start the process again.
The final, but least successful, form of grevillea propagation is through germinating seeds. The reason this method is not as viable is because the home gardener needs to understand how this process naturally occurs in the Australian landscape. Seeds can often be torn apart by birds and other wildlife, eaten and then scatttered by the same beasts in their droppings or invigorated by smoke in a bush fire scenario.
Just taking a seed and planting it in some potting medium will have very limited success. The seed, which is tough to collect anyhow, needs some pre-treaments if propagation is going to work. These may include smoking the seeds until they open, heating them in the oven or microwave, soaking them in boiling water, or cutting the hard shell exterior to allow the embryo to moisten.
Once all this has been completed you may have to wait anywhere between 8 weeks and 12 months before you can determine whether your propagation has been a success or a failure.
So, while grevillea propagation may not necessarily be the best way to increase your plant stocks at home it certainly is one of the last great challenges that home gardeners have in front of them. If you have the time, and the patience, then this activity may suit you. All the best.