I've been asking the same question for years.
You are right about bottlebrush and grevillea, Mackayboi. We planted all different varieties, and there are a few in flower all the time. Nearly all of them flower multiple times a year, all year round, and there are always bees in them. They say they are dry tolerant, but do like watering a couple of times a week, especially in the heat. Make sure you use native tree fertilizer or manure.
Michael, I think we'd be hard pressed to get any of those trees here, nor do they sound tropical. Gum trees of course grow wild..but would you believe..you can't buy them from the nurseries here anymore?? Apparently they are not currently fashionable. Gum trees vary of course, but some varieties flower every 7-10 years, some take 20 years to flower. Some seasons they will flower for extended periods. They are naturally the best honey source. I read in an american bee magazine about E. torwood, a hybrid. It's grown specifically for bees in Israel (I think, from memory). This would be ideal..if it's possible to get hold of! It's probably a subject for a different post, but where can you buy eucalypts in north queensland?
Bettertobe.. there are some things on that list we have here, such as pumpkin. Most of the trees are foreign to us.
Mek, I haven't heard of Tradescantia ‘Purple Heart’, but that article seems to suggest it is used to attract blue banded bees, not european honeybees. I think most of your suggestions are good...for native bees, that is. Mangoes are fertilized primarily by flies or stingless bees. That's why you hang a dead chook from the mango tree. Even so, I haven't seen my stingless bees work the mangoes here. I don't know enough about what is used in commercial pollination on lychees, paw paws and bananas, but I've only seen stingless bees on the banana flowers. I think A. mellifera like paw paws, and possibly lychees. If you are talking about jaboticaba, then the bees do love the flowers when they are out. It can flower a few times a year, but just for a couple of days at a time as you say. Awfully slow growing, but the fruit is terrific.
Mackayboi, don't think that you can plant enough to feed your hive. It's only supplemental feeding. You'll find they will be more attracted to whatever is out in the paddocks than what you spend time watering twice a week. Bees do tend to like citrus which grows well here. The smaller ground covers are a bit harder to maintain..tend to die off in the heat, and hard to keep water up to unless you have good irrigation system. I do have a few "morning star" bushes in the garden, which flower in full force every morning, and the bees love them, mainly for pollen I think. When you plant fruit trees, you will probably benefit from good pollination more than the bees will benefit from your efforts. By the way, there are lots of kinds of melaleuca, and some have masses of sweet bushy flowers. Fiddlewood is another dependable tree that flowers a few times a year, and is fast growing with lots of flowers. It might not be the best honey producer, but adds to the rations.
Does anyone know if bees like fig tree flowers? I don't mean the small edible fig trees, but those massive figs, such as moreton bay? We have a few young ones growing here, haven't flowered yet. But I imagine when they do flower there will be zillions of flowers. I might have to live to 150 to see it I guess.