What do you want to know?

Al

How fast they are growing? How often to transplant? Do i need to protect containers from freezing temp?
What kind of fertilizer to use if i plant them in gritty mix? How often to fertilize?

I'd say J communis grows faster than the average conifer, but HOW fast it grows will depend in part on how it likes the cultural conditions you provide. Containers don't necessarily need to be kept from freezing temps (the SOIL can freeze solid with no ill effects), but they need to be protected against killing low temps. I've left junipers out on the benches for extended periods down to 20* or so, with no apparent ill effects, but if you can keep actual root temps above 25-28*, you should have little loss of fine roots to cold temps. I fertilize when they are actively growing an soil temps are above 55* with Foliage Pro 9-3-6. Any of the commonly available fertilizers with a 3:1:2 NPK RATIO (different than NPK %s), like 24-8-16, 12-4-8, 9-3-6, would be a good choice. How often you fertilize depends on how often you water and mean temperatures. A full recommended strength dose per fortnight or a half dose weekly is about right when temps are above 55*.

Al

Thank you, Al, you are as usual very helpful.

..... and thank you for the kind words. I wish you well. Junipers aren't very demanding in containers. Try to avoid over-watering - they'll take it pretty dry; and in the dog days, try to keep the containers from over-heating. The heat often doesn't kill the plant outright in the summer, but those roots that are heat-killed often start to rot in the fall & your plants can collapse over winter from root rot.

Have you read the thread about tending to woody material in containers? It has a lot of good info in it.

Al

Here's the birth of a very small bonsai juniper from a 3 year old cutting I started:
{{gwi:10892}}
{{gwi:10894}}

Al

Here is a link that might be useful: More about trees/shrubs in containers ....