Help! Botanic emergency!

Does anyone knows the proper way to sow leptospermums (Manuka tree? Bush Tree??)

Because I am reading what I can find about it (not much), and they say that IT'S EASY. It is not easy! o_O

I think I've must have killed at least eight shrubs. The god damn thing gets attacked by this black soot, and white things -_- and puff!

And now another one is close to demise and I have all those seeds. Those tiny, minuscule seeds, and I don't know what to do with them.

The variety I have doesn't grow all that much. They must be about two meters. And this was it looked like when it wasn't dying -_-

Red Leptospermum:


Supposedly this is it:


Oh, and apparently when it's in danger it starts releasing seed as crazy. It means the "thing" is stressed. You know who is stressed?!

I think this is my third red one. Had two whites. And three pinks...