Grevillea Robusta

Grevillea "Pink Ice"

Grevillea Pink Ice, a Gem amongst the Gravel.

One of my favourite things to do where shopping for plants is to search through the “sale” plants at the back of the nursery. Not only because sometimes you can pick up a bargain but also because sometimes you can find a gem in amongst the rubbish.

Back in Autumn I was doing this and came across a Grevillea which had a label that indicated it was grafted and that was all it said. The only identification it had was “Grevillea Pink Ice” written on the pot with $28 crossed out and replaced with $15. This Grevillea caught my attention straight away as I wasn’t familiar with it. The good thing about it though, was it was grafted onto the rootstock of the Silky Oak, Grevillea Robusta. This meant that it would grow quite happily with the phosphorus toxicity in my soil. On the downside though, it didn’t appear to be doing very well as the potting mix was dried out and the thin needly leaves also reflected that it was really struggling.

The first flower for the season in August.

Never the less my curiosity got the better of me so I purchased it and took it home. Now normally when I buy a new plant I’m pretty quick to plant it but in this case I decided that it might need some pampering before hand so the first thing was to soak it in some Seasol for a few minutes. I then potted it up into the next size pot, left it a protected place for the last few months and then pretty much forgot about it.

Grevillea Pink Ice. Still narrow and sparce but I'll tip prune it after flowering so it will thicken for next season.

Then about a month ago it started to flower. The flowers in fact didn’t turn out to be pink as the name suggested but instead they are white which is reasonably uncommon with most Grevilleas you find in nurseries. Then again it has been groing in the shade for the last few months so maybe when it starts to get some sun the flowers may have a pink tinge to them but we’ll wait and see. The other option is that it might not even be Grevillea Pink Ice?

Anyway yesterday being the 5th day of spring I decided to go ahead and plant it. It’s still in flower with lots of small buds still appearing as well so it appears as if it may have a reasonably long flowering season. The other thing I like about this grevillea is that it does appear to have an erect growing habit which will make it fit in well in a small garden with lots of plants in it.

So looking at my purchase today I must say that I’m pretty happy with it. Whether it has pink on white flowers doesn’t make much difference to me. The important thing is that it looks like it will put on quite a nice flowering display, it is a little different to the other grevilleas in my garden and it should be very hardy and drought tolerant.

Grevillea Pink Ice Flowers and Buds

So next time you’re at the nursery have a look out the back and see if you can find a gem. You may not find the same one I did but never the less you may find one just as good as Grevillea Pink Ice.

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Posted in Grevillea | Tagged drought tolerant plants, Grevillea, Grevillea Pink Ice, Grevillea Robusta, Seasol, Silky Oak | 2 Comments

Silky Oak, what you really need to know

Grevillea Robusta aka the Silky Oak

The Grevillea Silky Oak is not only one of the most popular Grevilleas in cultivation but it also does have some features that are quite desirable. It does tolerate badly drained soils such as clay and will also tolerate some phosphorus toxicity in the soil as I’ve discovered in my own garden. It’s because of these features that it has become popular as a rootstock for grafting some (but not all) of the more difficult to grow Grevilleas and as such has enabled them to be introduced into cultivation in areas that once would have proven difficult.

The Grevillea Silky Oak also has a reputation for being one of the most adaptable Grevilleas. Despite growing naturally in the sub tropics in deep rainforest soils, near rivers and streams, it seems to have adapted fairly well to the cooler climates of southern Australia. For a rainforest tree it is considered to be drought tolerant and for a tree from the sub tropics it is also considered to be frost tolerant.

So there you have it that’s the Silky Oak in a nutshell, drought tolerant, frost tolerant and very adaptable. Sounds like the perfect tree to plant as a specimen. It’s also a tree that I greatly admire as I’ve seen some absolutely fantastic specimens of it in flower over they years but for me when I started my new garden I just couldn’t bring myself to find a place for it……..and here’s the reason why.

As you drive around you do see lots of Silky Oaks growing as street trees, in parks and in peoples front gardens. You see lots of fantastic looking specimens but for some reason you also see a lot that look like absolute rubbish. Now when I say rubbish I’m taking about the fact that there seems to be lot of Silky Oaks with branches that appear to be dead without any foliage on them……and here’s the strange thing. Quite often you will see a group of them growing in close proximity and they really appear to be a mixed bag. Some look fantastic, some look just average and others look to be quite good specimens……and my question is, why?

Well one reason might be because Silky Oaks do have a reputation as being semi deciduous in cold climates. This is true but some of these trees actually look like this during the warmer months as well. I suppose the important point is that some Silky Oaks are affected by this and others aren’t. So back to my question, why is it so?

The upper branches on the first Silky Oak have lost their leaves while others behind range from "doing quite well" to "struggling" like the one at the front.

These Silky Oaks are growing in Melbourne. The upper branches on the first Silky Oak have lost their leaves while others behind range from "doing quite well" to "struggling", just like the one at the front.

Is it because maybe they’re not as drought tolerant as their reputation suggests. Well my sister lives in central Victoria where the summers are a lot hotter and drier than Melbourne. She has a very mature Silky Oak growing in her front garden that looks to be handling the conditions very well and I also know for a fact that she never waters it so it just survives on the local rainfall. I’d consider this tree to be a very drought tolerant plant. Now the other thing about her locality is that they also get a lot more frosts there over winter so it would be safe to assume that this particular Silky Oak is also frost tolerant.

Now here’s the other interesting thing. Just a few hundred metres up the street there are some Silky Oaks growing as street trees under the same conditions as my sister’s Silky Oak and they are a real mixed bag. Some are doing fine and others have defoliated branches that look quite ugly. So, why does this happen?

The only thing that I can suggest is that the one thing that all of these Silky Oaks have in common is the fact that they are all grown from seed. As any gardener who like to propagate plants knows, when you propagate plants from seed you get variation. It’s just like a litter of puppies and kittens. When you go to pick out a puppy from a litter there will always be one that stands out from the rest, there will be the runt and the rest will be a variation somewhere in between. So it stands to reason that if you are going to propagate Silky Oaks from seed, even if you pick superior trees as the parent you will still get some variation in the ability of the new plants to withstand drought and frost…….and then again, if you were to use seed from inferior trees then the quality of your results will be even less again.

This was the only young Silky Oak I could find.

Now here’s the other thing that I’ve also noticed about Silky Oaks in Melbourne. The other day I drove around my local area looking for Silky Oaks and guess what……..I found heaps of them. They were everywhere. The one thing that they all had in common was that they were all very mature trees that had been planted 20 or 30 years ago. I couldn’t find any that were young of less than say 10 years old except for one solitary Silky Oak growing in a park all by itself. I even looked in new housing estates and couldn’t find any growing there either.

It appears as if what was once a very popular tree has now lost it’s popularity, and understandably so. There are just too many Silky Oaks out there in the gardens of Melbourne (and other places) that actually just look like rubbish, and I reckon it is a real shame. Growing these trees from seed seems to be a little bit too unreliable. So you have to ask, why not just grow them from cuttings?

Well it’s not hard to guess why. Growing Silky Oaks from seed is pretty easy. After flowering they set lots of seed and the seed also germinates fairly easily so from a commercial sense this is probably the most economical way. But as we’ve already discussed this also means that you don’t necessarily get the best trees as a result. The other problem is that a seed grown Silky Oak takes many years to flower. So if you want flowers you have to be patient and then when they finally do flower quite often the flowers are that high in the tree they can only be admired from afar.

On the other hand though if you were propagating cuttings from a superior Silky Oak the advantages would be superior trees, trees that flower at a much earlier age and most importantly the Silky Oak may once again become popular in streets an gardens again.

So there you have it. That’s my take on Grevillea Robusta, the Silky Oak. I think it is a very worthwhile tree to grow, but if you are going to grow it find an old tree that looks like it doing very well and take some cuttings and propagate from it. After all if you are going to spend the 10, 20 or 30 years growing a Silky Oak into a specimen tree then why not take the time to do it properly and just propagate it yourself.

Read more about Grevillea Robusta, the Silky Oak.

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Posted in Garden Plants, Grevillea | Tagged Grevillea, Grevillea Robusta, Silky Oak, trees | 22 Comments

Grevillea Robusta, an alternative way to grow.

In my last article about Grevillea Robusta, the Silky Oak, I wrote about the fact that seed grown trees often take some years to flower and the possibility that trees propagated from cuttings may actually flower a lot sooner. The other issue with Grevillea Robusta is the fact that most of the flowers are held quite high in the tree and are quite difficult to admire up close.

I’ve often wondered if there was something that could be done to solve this problem, especially since this tree looks so spectacular when in flower. This reminded me of a Grevillea Robusta that I once saw growing under some powerlines that had been pruned quite heavily to limit it’s growth. This tree was about 4 or 5 metres tall and had an wide canopy that actually made the tree look quite attractive. It occurred to me then and there that Grevillea Robusta was indeed quite receptive to heavy pruning.

I then decided to pursue this line of thought that then led me to the obvious idea that instead of waiting until the tree is 3 or 4 metres tall, why not just prune it right from the start and in an attempt to prune it into a bush rather than it’s natural tree habit. Now I must say right from the start some gardeners may be skeptical about the ability to limit the size of a tall tree such as Grevillea Robusta in such a manner. But then again if it is possible to do so by pruning it at 3 or 4 metres to keep it to no more than 5 or 6 metres in overall height then why couldn’t you just prune it at ground level to turn it into a bush that is 3 or 4 metres tall.

Imagine this, Grevillea Robusta grown from a cutting (from a superior specimen). Then successively pruned as required until it branches prolifically to produce a rounded bush. Then when it flowers, it’s covered in it’s trademark orangey, yellow flowers that extend nearly all the way down to ground level. Wouldn’t that just look spectacular?

So what I’ve decided to do is go ahead and do it. Now for me though unfortunately I haven’t got enough room to do it in the ground so I’ve decided to grow one in a pot and here’s what I did.

This wasn't the best specimen of a Grevillea Robusta I could find but it did have lots of branches.

First of all I went to a nursery to purchase a Grevillea Robusta. Normally I would have selected a plant with one straight single trunk but for the purpose of the exercise I decided to select one that had several branches on it already.

Next up was to take it home and then prune it encourage it to branch even more.

Then re pot it into a larger pot, add some water granules so it is always moist and also some low phosphorus native fertilizer so it never goes hungry.

The idea here being to pamper the plant (something I don’t normally like to do) so as to optimize it’s growth potential.

Grevillea Robusta, now pruned and in a larger pot full of water granules and Native plant fertilizer.

The other thing to mention here is that the plant that I’ve selected has most probably been grown from seed so it may take some years to flower. The important thing though is that I’m trying to see how much I can get it to branch into a shrub rather grow into a tree.

As far as flowering goes though, what I intend to do is find a Grevillea Robusta that is mature and does appear to be a good specimen tree so I can try propagating it from cuttings in an attempt to then compare it against the seed grown one. So over a period of time there can be a comparison between the flowering and the growth rates.

This of course will take time but in the meantime my main objective is to just to see how much I can get this Grevillea Robusta to branch while growing in a pot.

So there you have it an alternative method to grow Grevillea Robusta but a while ago I saw something that made me think there may be another way of growing this tree.

As I’ve said before, Grevillea Robusta is quite often used as a rootstock for grafting other less reliable Grevilleas. Not long ago I was in a nursery and saw a grafted Grevillea with a scion that wasn’t growing very well at all. As a result the Grevillea Robusta rootstock had started to grow a shoot just below the graft that was actually doing better than the scion.

This then led me to wonder if you could actually coppice a mature Grevillea Robusta that was struggling as described in the previous article to rejuvenate it and then maybe grow it into a shrub as suggested above. I then went home and researched it and what I discovered was that it wasn’t considered to be a tree that you could coppice. Nevertheless that grafted grevillea had in fact grown a shoot just as you’d expect a coppiced tree to do so. So maybe it is possible.

Now I wouldn’t advocate for a minute that somebody should cut down their Grevillea Robusta to find out. But on the other hand, trees do from time to time get old and do get cut down because of it. This would in fact be a perfect opportunity to leave the stump in the ground and see if it does re shoot. You never know, you may just end up with a new plant because of it.

So there you have it. Whether you’d like to grow a Grevillea Robusta from scratch or if you’d just like to rejuvenate an old one here’s a couple of alternative ways to grow it.

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