Hello,

I just received a 50lb bag of Osmocote 15-9-12 fertalizer and I live in San Diego, CA. I accidentally ordered the 8 to 9 month slow release fertalizer. My question is, is it too late in the growing season to apply this lengthy of a slow release fertalizer to my acer palmatums? They are 2 to 3 years old in stage one developement and I live in Zone 10a.

Thank you Bonzai Empire.

I would not use that on any of my mature bonsai, but for seedlings like you have there is no reason why not. 

Thank you m5eaygeoff,
They're my practice trees but I'd prefer not to kill them lol. I appreciate your time.

The thing with osmocote is that it is control release. The warmer it is and the more wet it is the more fertilizer is released. Making it releasing when your trees need it. In winter not much is released and it will start when spring comes. I use osmocote on all my trees. 9 months just say it is slow release. In a normal temperate environment it will last longer as winter does not count.

Thank you Tropfrog,

That sounds perfect then because I was worried that my trees would be over fertalized during the winter months. And also I feel better about using on a few of my original trees that are between 7 to 9 years old that I'm letting grow freely for a couple years to try and get a little improvement on their trunks.

Cheers!

It is traditional lore to stop fertilization in the winter. There was a member here a few years ago who had a PhD in biology or something like,e that who said that the trees benefit from nitrogen all year long. 

Take your pick. Fertilizer is relatively cheap. Around here the winters are temperate enough that there is probably root growth all year long, so fertilizer probably helps all year long. I doubt it would hurt the plant unless it is seriously over applied. At worst it costs a few dollars.

Osmocote Plus is very good, I use around here too, mostly for developing and thickening trees, because you know, depending on how active they are, they can give you big leaves and internodes, but like Tropfrog said, osmocote need some warmth to release efficiently, so if you use it on winter there won't be any major problem, but it won't release much the nutrients if too cold either...

So for that reason I fertilize about autumn one more time and then I wait for next spring to start fertilizing again, even because the osmocote will still be there for the whole dormant season.