I cant be certain but that could be a fungal problem; I had a h. laurina growing for about 5 years (reached a height of about 4 to 5 metre) and also noticed some of leaves occasionally had that red marking; it didn't affect the flowering or growth in any way. Mind you, I had it in a very well drained (somewhat sandy) soil in an open garden position and once it was established let it rely only on rain fall for water - quite often the soil seemed bone dry. From your description, you are growing this in a completely artificial environment and given that h. laurina is a native of Western Australia, and as such, like many natives from that part of the country, can be cantankerous outside it's native habitat. Humidity could be the cause, Western Aus is known for it's aridity, and for that reason many natives from there will not grow in the (humid) eastern states, where I am. Sorry I can't be more specific.

Thanks for the input funnelweb. I'm in the US, and do have the plant in an artificial environment - less than ideal for any plant I suppose, but I was particularly captivated by this plant the first time I saw it, hence my interest in growing it. I suppose my largest concern with the reddening of the leaves is that it seems to spread. If it were just on a few of the leaves, perhaps as a result of a brief period of stress, it may not be as big of a deal. But the symptom is showing up on more leaves and seems to 'grow' larger. Did the red color on your tree ever cause leaves to drop?
Would you mind sharing what happened to your H. laurina after 5 years?
I guess I'll try to be patient with the tree unless someone else has further insight.

You might find this link helpful. It mentions that the soil should be lime free.

Here is a link that might be useful: Growing Hakea laurina

Yeah, tropicbreezent, practically ALL Aussie natives prefer a neutral to slightly acidic soil environment. Hakea laurina, Cyto.... is one of the few W. A. natives that are fairly hardy in that with care they can be successful outside their native environment. The red on the leaves of mine wasn't a problem in that it didn't particularly spread nor noticeably affect the plant. The tree didn't flower well though, in fact I had to look for the flowers even in its best year. The flowers are nice and unusual but (in my garden) not spectacular. The growth of my specimen was sparse, as many Aussie natives are, and it didn't die of natural causes it just became awkward in it's spot so I removed it root and all. It was originally a pot grown specimen.

@tropicbreezent- Thanks for the link. I suppose I could test the pH of the growing medium, but I don't believe it'll contain lime because the main components are inorganics and pine bark (with some peat moss). I've read the pine bark can acidify soil, so if that holds true then this growing medium should be in a more acceptable range for the H. laurina.

@funnelweb - I'm a bit discouraged by your flowers being underwhelming; the pictures I have seen online really grabbed my attention. I hope the H. laurina is hardy enough for my conditions! The growth seems to have slowed down in the last month or so, so it might not make it. I'm going to switch to distilled water and see if there are any changes.

Will post updates.

Other advice and suggestions are most welcome!

A lot of Protoaceae are susceptible to Phytophora fungus which has become a big problem in WA. It might be worth looking into that angle. In a pot that should be treatable.

Yes, dunno if that's a problem over in the US Cyto.... , I think that's what took out my Banksia coccinea last year - I had it for 4 years and it flowerd every year; also my black kangaroo paw, macropedia fuliginosa. It only lasted a year but got one burst of flowers, and that made it worthwhile. I'll see if I can get my pic of it to post. Spectacular thing really.

So I think my issue may be phosphorous toxicity. I'm not certain, but I read an article (http://www.sciencedirect.com/science/article/pii/S0304423808001544) on this topic and they state that accelerated leaf senescence can be a symptom. This sounds like what I'm seeing (http://en.wikipedia.org/wiki/Plant_senescence).
So when I applied an aqueous fertilizer to the plant - thinking that it was deficient in some nutrients - I probably exacerbated the problem. I've been watering with distilled water because I anticipated that the toxicity might be an issue; the hope is that I can flush out some of the nutrients - not very likely, but worth a shot.
I guess my concern for the plant being deficient in nutrients was strengthened by some symptoms of phosphorous deficiency (http://www.extension.uidaho.edu/nutrient/crop_nutrient/corn.html).
Jeez... I'm really not sure where to go with this.

I don't think fungus, or root rot, should be a problem because the growing medium drains well and I let it dry-out prior to watering. I guess I'm not too familiar with the plants natural conditions, despite all my research. It's quite possible that it needs even less water than what I give it, but I don't over-water it as best as I can tell.
On topic of the natural growing conditions, could one of you explain more about the soil that Australian Natives grow in? This may help me prevent this issue in the future..

Wow funnelweb - I just looked up those plants you were talking about; haven't seen anything like that before! Are those species also native to Australia?

Yes, they are Aussie natives - specifically native to Western Aus. about 3,000 miles from where I am. As I mentioned, it is difficult, extremely difficult, even if the plants are grafted on hardy stock, for some them to perform outside their natural environment - which, in plant terms, is tough. The focus of this discussion, by the way, hakea laurina, is nowhere near as difficult as many others, and I've tried a lot. So you are up against it. My most successful is (a few of the) eremophila genera. I'll try a pic. of one: This eremophila macmilliana. It's rare in the eastern states, and while the flower is insignificant the foliage is a gorgeous pale gray. Oh, and this one is grafted.

Here is an update:

I have continued to water the Hakea with distilled water. The intent is to flush out nutrients (or at the least make an attempt to lower nutrient concentration). The 'Cluster roots' common to proteaceae are especially efficient at uptaking nutrients - this leads to an increased chance for toxic levels of nutrients which may lead to premature senescence (which I believe to be the problem my hakea is experiencing) among other things.
The first few weeks of flushing the pot with distilled water resulted in a growth spurt (albeit a relative small amount of growth). Additionally, the senescence had halted on the older leaves (ie leaves before new "growth spurt"). While this seemed promising, the hakea has once again halted its growth and has continued with senescence (or what I believe to be senescence). It seems to be spreading faster through the "older leaves" but does not seem to have effected the leaves from the "growth spurt" yet. I am not too optimistic about this hakea's survival - she's looking rough!

I would still appreciate any advice from people ho have experience with hakeas or other proteaceae.

Also if a reader would be so kind as to provide me with a better description of the soil that constitutes native Australian soil, or soil that Australian natives naturally occur in, I would be very grateful for your time & assistance.

Until next time,

James.

The climate where the plant comes from borders mediterranean and maritime. Unfortunately, the soil over the whole area would vary quite a lot. Makes it very difficult to generalise. Obviously the plants would grow where seed falls in a suitable environment, and wither where it's adverse. I was down there last year but don't remember seeing that particular one. Although, I did take hundreds of photos of wildflowers.

That link above is from the National Botanic Gardens in Canberra. The climate there can be quite cold as it's up in the mountains. The soil is mostly heavy, clayey, but in the gardens they would no doubt set up artificial beds for different plants.

Mine grew in well drained sandy loam. Being in Aus. I certainly didn't give it any special treatment, just bought the thing from a local (natives specialising) nursery, stuck it in the ground and off it went. Most Australian natives don't like to be fussed over too much, just ensure the growing medium - and perhaps the climate - is suitable and let it do its thing. That might be easier said than done in the US but also Cyto.... there is nothing spectacular about that variety of Hakea, others of the species have far more showier flowers; H. Burrendong Beauty, a bush, a typical example.
B.
PS. Oh, and yeah, both those plants mentioned above are Australian natives, mind you, the black Kangaroo Paw is very particular where it wants to be planted, and in these eastern states you can't expect more than one season out of it - too humid. Similarly with the Banksia coccinea, though I managed mine for about 5 years. They are particularly prone to phytophera fungus, a soil born disease, which, I understand is becoming a problem in the west also: they have very rigid quarantine laws over there.