How heavy are you on the *fertz* - somewhat dependent on what type of container mix one uses as well......granted it is time release and probably leaches out I just received a pic from a grower on a cultivar I was interested in. Granted this stuff is generally in fast draining mixes but I'm always kinda-sorta blown away by how heavy the *prills* are on the pots. In the pic I received today, I would easily 1/6 of the top surface I cannot see the container mix but it's covered in pills.
I have about 10% of my maples in pots, and I re pot every 2 years, sometimes 3. I only use a 'little' controlled release fertilizer in pots that have compost/soil that is over a year old. Maples that have been freshly repotted don't need anything IMO. I have found that over feeding gives too much leggy growth and very long internodes, which ends up having to be being pruned back in the summer.
As well as the leggy growth mentioned above, over-ferting can result in soft growth that does not harden off before winter, resulting in branch dieback and routes for opportunistic bad bacteria and other pathogens to infect your JM. The more frost you get in your region, the greater the risk. The professional growers often grow under cover so they can get away with the heavy ferts. Buyer beware for maples moving from such a situation to a real world proper winter. In my personal situation I want my container maples to grow as little as possible while still remaining healthy, so feed is usually some kind of organic slow release which is not high in nitrogen.
I did create a video showing how we fertilize all our container growers each year. The correct type and the correct amount are very important
I primarily do containers for - getting plants to size so that if the rabbit or deer nibbles it, I still have something left...so if I get something a bit small....I container it for size before it goes out. I don't use -compost- presuming we are talking the same wording, but generally bark/pumice with a smidge of peat in the mix. Re: containers. I kinda approach it 3 fold...mainly as my potting medium, everything drains out. I will use Time Release...afaik, it does have some micos'macro's covered. Occasionally I will feed it with some liquid very ultra diluted since it is a -lifeless medium- In the most expensive as the last thing, I have a big 40lb bag of micro's/macros, I do incorporate as well into the medium ....as per the previous sentence before, it's a pretty sterile medium
I have received one JM from a grower who must have been high on N. I'm leaving it alone for now....as while it has good thick bones....the top frame is 4-5 really long shoots with just leafing primarily at the end of the tips. So long, it weeps down....but I don't want to *prune*, *top* it, as I don't want to remove the apical growth....subjective opinon I suppose on the comment of -removing apical tip- I suppose
Just another opinion and approach - I use absolutely no fertilizer ever for container maples. I've been doing it for 20+ years and have been successful. I prefer a compact growth form on pretty much any cultivar when container grown, and also strive to keep them happy in the container as long as possible without re-potting.
@kines , that is a great approach for sure keeping the task entirely up to mother nature. Obviously you are keenly aware of the type of soil mix to use and when to repot based on how the tree is visually doing as it becomes more and more root bound. We always have used a small amount of a 6 month slow release fertilizer each spring only to ensure the soil is getting additives that it may not receive by being in a container year after year with the same soil.
The forum is back now that I'm getting notifications.... Still pruner shy and don't want to go Edward Scissorhands. I'm debating what to do with these long growth that weeps when it rains...it's hasn't -naturally grown- slow with thick stiff supporting itself. Don't want to prune it as I don't want to stop apical growth. Thinking I might throw 4 stakes and tie them so that remain vert and let them harden off through winter to remain vert ?
