AusBonsai

I have difficulty keeping good colour on Japanese white pine (non grafted ones) and some scots pines in winter. They go yellow. I have tried various elemental foliar sprays (still on-going) Results have not been very encouraging so far. I have sprayed Molybdemon and Manganese so far on two different lots. I figure that because the chlorosis is one older leaves, it probably is not deficiency in iron, copper or zinc. I could be wrong. Possible it's nitrogen but I can't imagine how. They green up when warm weather returns. I don't have the same problem with Black pine. I have noticed it in some natives however as well as some other plants. I expect it to happen in citrus and gardenia - that's quite normal, but cold climate trees??
Anyone have any ideas?

I see yellowing on black pines but that seems to be due to lack of feed - probably nitrogen and is especially common on the pines that have not been repotted for a few years so it is hard for nutrients to penetrate into the root ball. I can't see that as being the problem with these pines at your place Mike as you know as much as anyone about correct nutrients and potting.
As you say, it is a common problem in citrus in winter and reported to be due to nitrogen deficiency because they are subtropical and the roots just don't work properly when it is cold and connot take up N even if it is available. Again that should not affect cold climate trees as we expect their roots to work even in cold soils.

I only have a couple of seedling white pines but I have not noticed yellowing on any of them. I repotted one today and it looked fine. I'll have a closer look tomorrow now that you have mentioned this.

Just some food for thought Mike. Winter in Japan is the same where their Goyomatsu also go very golden yellow so I think it's perfectly normal and healthy. I do have a couple dwarf whites - Hagaromo, where one is way more exposed than the other, the one in full sun is very yellow wherea's the other that gets probably too much water run off from my decking and more shade is classic white pine green.. !!

Have you used Epsom salts?

I’ve only really noted ugly bronze colouring on my Hinoki and junipers and the salts helped turn them dark green / blue.

Robsterios wrote:Just some food for thought Mike. Winter in Japan is the same where their Goyomatsu also go very golden yellow so I think it's perfectly normal and healthy. I do have a couple dwarf whites - Hagaromo, where one is way more exposed than the other, the one in full sun is very yellow wherea's the other that gets probably too much water run off from my decking and more shade is classic white pine green.. !!

Hi Rob
Yes I have noticed (from pictures) some white pines in Japan do look yellow in winter and yet others which are being exhibited during winter are perfectly green so although it seems to be a common problem I'm not convinced that it necessarily ok and cannot be rectified. There's no doubt that shading them keeps them greener. Why I'm not sure. It might have something to do with destruction of chlorophyll by ultra violet light that somehow does not affect them in summer. Anyway, I've moved mine under plastic cover and fed them with a complete micronutrient solution as well as sprayed them with the same and fed a little N as well. We'll see what happens....

Daluke wrote:Have you used Epsom salts?

I’ve only really noted ugly bronze colouring on my Hinoki and junipers and the salts helped turn them dark green / blue.

Hi Daluke, yes I have given some magnesium as well. The bronze colour on junipers is not the same as this. That bronzing/reddening is the plant producing anthocyanin pigments in the leaves to protect itself from cold/light. Quite normal for a lot of plants but apparently pines are not capable of doing this. It could be a clue though.

I believe the yellowing needles in japan is normal. Those you see in the exhibitions have been wintered indoors to keep them green for the show.