what is the best way to propogate seeds and can they survive cold climates/ snow?

Down here, Jacarandas seed themselves very readily. Get the seeds, plant them in sandy soil, keep moist and very warm.

They're not hardy, though and don't survive below about 30deg. F for any prolonged periods. We do get the odd frost here, and the jacarandas are dormant when that happens, so the larger trees are not harmed by frost. Smaller seedlings would certainly die without frost protection though. You'd need a greenhouse if you wanted to raise them from seed, I would think.

Could you please put in a more specific location (city, country) into your personal profile? "Europe" covers a huge range of climates. Welcome to garden.org by the way!

In Arizona in zone 9B I've managed to kill a few of them. When young, they do need to be protected from frosts. After they're older, they do fine. Any climate colder than this, and it would be quite risky. They are beautiful trees. I envy you being able to grow them, Elaine!

Sadly, we had large, leaning Jacarandas when we bought this house, and had to have them removed. They're not strong or deep-rooted trees. So I've been just enjoying my neighbors' trees the last few years. I can see one in bloom right out my window here.

There are still seedlings from those trees that pop up in my garden (or possibly from the neighbors). But always too close to the house.

It's nice that you can see one. That's good enough Our neighbors had an old one, and I just noticed that they must have taken it out. My view of it is gone.

Why do some jacaranda trees show a nice symmetrical shape with tightly borne flowers and few leaves visible, while other jacarnda trees (of the same size) ,show few flowers and mostly leaves ?

Not sure, but I've noticed the same thing here. It might be something to do with how much water the tree is getting, that it grows and blooms differently. If a tree is in an area that gets some irrigation it would probably bloom differently than one that doesn't get any water except the rain.

Here the Jacarandas bloom usually in April and the bloom is much longer and more luxuriant if there's been a fair amount of rain. This year most of the trees bloomed sparsely for a pretty short time. We had 8 months of drought and it finally just started to rain this week.

I think you're on the right track, Elaine. I love them and am always checking them out here in AZ. Most are pretty sparse and full of leaves with just a few blooms. We don't get much rain, and many of them aren't in irrigated areas. I've never seen one growing well here.