Juvenile growth on junipers…Cut? Leave alone?
I’ve received several emails about how to handle juvenile foliage on junipers, and felt like this was one of those discussions that could be useful to a larger group of people.
- Juvenile growth in junipers is when the shoots display needle-like growth on a typically scale growth variety (a few of those are listed below).
This is Rocky Mountain juniper, a scale juniper, showing the past year’s growth as the spiky, juvenile foliage, with the tips transitioning into mature, scale foliage.
Spiky juvenile growth is a response to either too much foliage loss from pinching (don’t do that), overly hard pruning, or sometimes too much fertilizer. Naturally, since mature scale foliage is nicer to look at, and is what the tree grows when it’s content, we might have the impulse to cut the juvenile off.
- Don’t do that. Leave the juvenile foliage alone.
- The problem is, if we cut off the juvenile growth, we’ve likely cut off everything that is new growth on the juniper. And that would be deeply, seriously, and really quite intensely bad. A juniper needs its newer foliage to stay healthy and strong.
When the tree is ready, it will grow scale foliage on the new tips, replacing the juvenile. The needles of the juvenile foliage will over time yellow, brown, and eventually will be shed. But, it can be a year or two impatient wait for this to happen. You might want to stock up on gloves so you don’t nibble your fingernails off.
Of the clearly scale-type junipers, Itoigawa is one of the most guilty in how it so easily reverts to juvenile foliage after an over-strong pruning. Rocky Mountain can revert to juvenile. So can Sierra. Shimpaku is one of the least susceptible.
In short: Leave your juvenile foliage to its own devices, concentrate on other trees to dilute impatience, and try not to repeat past juniper offences.
For more about how to maintain junipers, please see the post Never Pinch Junipers!
11 Comments
Reblogged this on Bonsai Eejit.
Hi Michael, great article on juvenile foliage, as was your previous article on not pinching junipers and the distinctions in treating growth on scale versus needle junipers. I have a related question. I own one Italian Stone Pine, and I was told by the person I bought it from (now deceased) that it should be maintained much like a juniper. In the six or seven years that I have had this tree I have never been quite sure how to prune it. Right now, it is growing outside in full sun, and its new shoots are elongating. I would like to train the tree to be more compact and encourage ramification. Can you tell me how to do so? Should it be treated similar to a needle juniper?
The Stone Pines are curious creatures. They will want to grow juvenile growth in a pot, in preference to their normal mature needles. This juvenile growth is essentially bract-like growth, like the first foliage on a decandled black pine is the same thing, before the needles come out. Looks like cedar.
I don’t have any experience with the Stone Pine so I’m hesitant to offer advice. I do know that some people keep it juvenile. With the climate you’re in, I’d think you’d have a chance at getting the mature to come out. Still, I’d be very reluctant to treat it as a needle juniper to get ramification. If you do, you will probably get the ramification, but maybe don’t use it as a yearly technique.
Bingo! Well said by Michael. One more thing I’d like to add is that Rocky Mountain Juniper may also revert to juvenile growth if it has had any issues with fungus, wether you touch the tree or not; recently collected trees are already weak and more prone to getting Phomopsis.
Reblogged this on Wolf's Birding and Bonsai Blog.
Thank great info!!
Ron
Very Helpful as always.
“Let nature take its course”; we’ve all heard it said countless times. So why don’t we listen to our trees?
Because we’re too busy talking?
I repotted a RMJ this past winter. It was collected material by Randy Knight. I have been fertilizing it like my other trees; organic in tea bags and Maxsea 10-10-10 every other week during growing season. I live in San Francisco. The RMJ has put out a lot of juvenile growth since the repotting. I was told it could be the spurt of root growth after repotting. Would you advise less fertilizer? I have done zero pruning.
You could try just the organic and no Maxsea, and also be sure the tree is really drying out a bit before watering. It may well be a result of the repotting, put it in the very best sun that you have, and hopefully in a year or so the foliage will revert to mature. Be very alert to Phomopsis tip blight in San Francisco.