Tagasaste/ tree lucerne

I first encountered tagasaste on YouTube,  where I learned it is  widespread in Australia and NZ. I was immediately intrigued. A fast growing and tough perennial shrub,  evergreen, high protein fodder and pods for almost every conceivable type of livestock, nitrogen fixing, good firewood... a Swiss army knife in bush form.

Rare to find all those qualities in any single plant outside of the tropics.

So far I've only found one seller in the US and very limited information as to its suitability in our different zones.  Supposedly it's hardy to zone 8 but I was wondering if any Americans here have had any success sourcing and growing it here.

I tried to grow it multiple times once I found seed, both in Georgia (zone 8) and California (zone 9).  In both places it froze to the ground after any kind of hard frost.  After a mild winter in CA the last one got to maybe head tall, but was never very vigorous (no branch thicker than a pencil, so not much fuel use either), even with irrigation.  There were way more vigorous forage plants available in both places.

I planted some seeds at the edge of a garden bed, intending to transplant them later if they came up. The bed had compost and was irrigated. 2 years later the trees are nearly twice my height!

These trees survived through the coldest winter I've ever seen here, not sure how low the temperature got (probably no lower than -7ºC/19ºF), but the ground was frosted over without thaw for several days in a row.

I am about to start off more seeds, this time in seedling trays, this time around being very strict about transplanting them.

Before sowing, the seeds need to have special treatment. Putting them in a bowl and pouring water over them and leaving it to cool for a few hours is the best treatment I've found. But sometimes they can be tricky to germinate.

We've had tagasaste trees growing for upwards of 20 years in an Australian "Mediterranean" climate - seldom below 5°C and up to 40°C plus for short periods.   They haven't reached what you'd call "tree" status in all that time.  Multi-branched and still not robust, but leafy and hardy since they weathered last year's drought conditions unscathed, unlike some of the native plants.  There's something about the flowering period that makes them unpalatable, at least for cattle, but definitely very attractive to bees. It may be that it needs to be planted on upland away from frost hollows in areas where lower temperatures can be expected.  Definitely worth trying to get them started if you can get the seeds, or plants if shipping between states isn't a problem.
Edit to add:-  I went looking. . . https://permies.com/t/174914/Buy-Tagasaste-Seeds