Juvenile foilage?

What happens to juvenile foilage on a juniper? Does it change into mature foilage, or does it stay the same and mature foilage start growing from the buds and nodes in the juvenile foilage? I've never spent much time with junipers and recently picked one up.

As mature foliage grows on the tips of the branches, the juvenile (spiny) stuff browns and falls or gets rubbed off.

If I may.. Maybe it would be good to expand on the initial post..
How does one reduce / prevent juvenile foliage? (I have a very nice Ittoigawa juniper, first styling a good year ago. Now full of juvinile foliage.)

Juvenile foliage is a sign of stress. In my experience, excessive pruning is usually the culprit and the only remedy is to let the tree recover and grow out. Certain cultivars are more likely to develop juvenile foliage then others and I believe Itiogawa is one of them.

Cure for juvenile foliage - put the scissors down and step away from the tree. Excessive pruning is the main cause, and the only cure is let the tree grow.

As a general guide, for Junipers removing as little as 20% of the foliage can cause juvenile foliage, though it won't always happen, other factors play a role, including health of the tree. Some revert when you take the scissors out of the tool box, others will almost never revert.

For the health of the tree, be cautious and make sure your after care is excellent any time you remove more than 30% of the foliage. Drastic reductions should only be done during major re-stylings, and then the tree needs time, often more than one growing season to recover.

I'm growing in zone 5b, the great white snowy north, My junipers are buried in 2 feet of snow right now. It will drop to -5 F (-20 C) Saturday night, I love that my Kishu and Itogawa have no trouble at all with cold. But because I am so far north, I can not ''get away'' with treatments the California and mild climate growers use for their junipers. In mild climates you can be more aggressive working junipers. I have very little trouble with reversion following my 20% guideline. Admittedly, there are times one needs to cut more, but for routine maintenance of shape, this seems to work.