Tropical Zone Gardening: Grevillea "Long John", 2 by Anniesfollies

Anniesfollies wrote:
This is a rather old thread so I hope someone will see my new post.

Three years ago I planted a beautiful 15 gallon Grevillea ‘Long John’ and it has done nothing but go slowly downhill since then. It was planted as a focal point in the garden with the expectation that it would grow, bloom and be a beautiful plant to see coming in through the entry.

At this point is still as tall with the same two main branches and it has a few blooms in late winter and spring, but small side branches have gradually dropped off, no new ones have grown, and it has only about 20% of the foliage it did when purchased. I'm in zone 10a/b, and in summer it gets a little morning sun and then shade the rest of the day, and in winter it gets sun about 2/3 of the day. The few leaves it has seem to turn yellow and die, although it does get a few replacements. In researching yesterday I found that they can become yellowed in alkaline soils (which we have) but applications of iron sulfate or sulfur will correct the problem so I plan on trying that. However, I don't think that's the only problem but I'm not sure what to do. It has had no fertilizer.

It's on drip irrigation so it doesn't get overwatered, but our drainage isn't great as you hit extremely hard ancient seabed about 14-18" down and in places need a jackhammer to get through it. Most other plants do fine but I know Grevilleas don't want to be wet.

So I don't know if it's lack of sun, poor drainage, or our alkaline soil that is slowing killing it. I'm wondering if it should be moved to the sloped part of the yard which has good drainage and potentially more sun, or would it do okay in a large (almost 20" box size) terra cotta pot? I've included two photos, one showing the plant and one with a close up showing the yellow and dead leaves.

Any advice would be greatly appreciated.

Please excuse the sideways photos, can't figure out why it is always doing that lately.