Juniper Foliage

[hawkforce]

My mother has a juniper in the ground and a few months ago I noticed a change in foliage. Changing from lil spikey tufts into long tight needle like foliage. It was the tight needle like for a while, now it seems to be changing back to spikey tufts. Like the needles are unfolding? I think younger growth is spikey and more mature growth is long thin? It's what I see on one of my potted junipers. Question:what causes the changes in either direction? Does it have anything to do with fertilizer? Shock? Watering? And how?
Thank you all for any help and I'm in a 10-B ag area. Thanks, image is of mature?

 

[Wires_Guy_wires]

We like calling it scale 'adult' foliage and needle 'juvenile' foliage. That makes it easier to keep apart.

Needle foliage on junipers can be caused by a couple things. One of the key takeaways is that needle, or juvenile, foliage is photosynthetically more active because it has a larger surface area. This means it loses more water. It also hurts more when you rub against it.

Junipers produce this needle foliage in a response to the following: a high activity (as in growing fast, especially in younger plants), a response to grazing (to prevent future grazing for a while), as a response to heavy pruning, as a response to shade (more activity needed from the foliage that is there).
Scale foliage tends to return after a one or a couple years in stable conditions, unless there's a lack of light. Then they tend to stay juvenile.

 

[hawkforce]

We like calling it scale 'adult' foliage and needle 'juvenile' foliage. That makes it easier to keep apart.

Needle foliage on junipers can be caused by a couple things. One of the key takeaways is that needle, or juvenile, foliage is photosynthetically more active because it has a larger surface area. This means it loses more water. It also hurts more when you rub against it.

Junipers produce this needle foliage in a response to the following: a high activity (as in growing fast, especially in younger plants), a response to grazing (to prevent future grazing for a while), as a response to heavy pruning, as a response to shade (more activity needed from the foliage that is there).
Scale foliage tends to return after a one or a couple years in stable conditions, unless there's a lack of light. Then they tend to stay juvenile.

Thank you. That's helps me understand it better. I really appreciate the help you and others have given me.

 

[Wires_Guy_wires]

One other thing I didn't mention is that large influx of auxins can also push scale foliage to produce needles, for instance when we air layer or take cuttings while using rooting hormones.

Some junipers are more prone to needle production than others. Regular chinensis in my book hardly ever does so, itoigawa tends to do it faster but also reverts back to scale within a year, sabina seems to be similar. Blaauw, media/pfizer/tamariscifolia/mint julep, US procumbens, scopulorum, phoenicea and virginia tend to go juvenile pretty easily and can take a long time to revert back.

I mention US procumbens specifically because here in Europe they never produce scale foliage.

 

[leus]

Down here in Chile Procumbens pretty much stays juvenile a long as you prune or pinch it, so for bonsai that’s pretty much always. It used to bum me but now I kind of like it.

 

[Leo in N E Illinois]

In Florida the 'San Jose' juniper was commonly used for landscaping. It switches between juvenile spikey foliage and mature scale foliage very easily, almost any time it is pruned.