Hi! Last month, I looked at most of my maples that are in pots to check which ones needed to be repotted. I've slip-potted a few of them into a slightly larger pot. However, today I've realized I forgot to check my big Koto no Ito! And to my horror, I could see that the tree was extremely pot bound. What would you recommend me doing? Since the tree is now in full leaf, is it too late to put it in a bigger pot? If not, can I just slip-pot it (leaving the the root ball intact)? Or shall I do something with those roots that are going in circle? The bottom of the pot is really full of roots, and probably not much soil. If it's too late to report, shall I properly feed it? Or shall I just wait for next year to do the repot? Thank you
Good evening Chris, I would definitely only slip pot it for this year. Then make a note to re pot next March. You could re pot in the Autumn, but I prefer early Spring tbh. Re feeding, I would just give it some good John Innes no 3. There is enough feed in that for 12 months.
Different strokes for different folks. My approach is the opposite of @Acerholic, I always wait till the first flush of leaves is fully expanded, and repot then - which is usually May in my area for outdoors trees. The reasoning for this timing is that the tree has just finished a transfer of energy from the roots to the canopy and is now about to enter a period of root growth, meaning the maple is naturally in the right mode for roots to establish quickly. I wouldn't recommend major root pruning at this stage but minor root pruning is OK and root teasing is fine. At the end of the day Japanese maples are fairly forgiving plants and can be successfully repotted in most months of the year in a mild climate such as UK. Obviously you would avoid extreme heat conditions if possible. To paraphrase a famous gardener - the best time of year to repot is when you have the time.
Thank you @Acerholic and @maf for the information! I'll look for a bigger pot and will probably slip pot into in, and won't do major root pruning. I'll probably remove or move only the few roots that are circling the pot near the the surface. But hopefully as Easter's bank holidays are coming, I might find the time to do it then When redoing a proper repotting in March, is it when you could remove some good amount of soil, cut some of the roots at the bottom? I have a book from Larchfield (Neil Kenney) and it shows how he prunes a good amount of the roots (10% if I remember), is it what normally repotting is about rather than just slip potting?
Root pruning is fashionable but not mandatory. (Except for bonsai where it is mandatory lol.) You could repot a JM every 2 or 3 years into a slightly larger pot almost indefinitely and never root prune and still have a healthy container plant.
However, it is a bad idea to leave circling roots as is. IMHO, at least loosen all roots on the surface of the root 'ball' or make a few vertical slices through those 'pot wall' roots.
@ChrisUk I always root prune when repotting. I do this every two years for all my pots. But as M @maf days its not mandatory. I find it invigorates new fine root growth and also allows me to use the same size pot and add a nice amount of fresh new soil. 10% is a good guide, but sometimes I remove more than this. Agree with J @0soyoung that circling roots are not good to leave.
Right. I use a sort of 20 cm rake to untangle the circling roots and cut them. Then a stick to untangle the rest of the rootball and add some new soil, mainly pozzolan and composted bark, but also a bit of compost, and add some slow-release fertilizer. So far, so good, even when they're in full leaves. Of course, it works with my trees, in my climate, with my soil, and I can't tell you when is the right time or not to do it where you are, or how much of the roots you can remove. Somehow, you have to "feel" when it's the right time to do any work on your trees. But it works here...
Thank you everyone, for all this information! At least now, I'll be more prepared and organized next year. I'll try to find a slightly bigger pot this week end, and will start to repot it, and untangle the visible root circling round the pot (surface and bottom). I've also noticed today another job that I need to do now.. Lots of maples have lots of aphids! It will be a quite time consuming job. I'll try to take some photos (not of the aphids ;)) and post some in the spring thread, as now lots of trees are leafing out very well.
My latest treatment : ignore them. On maples, they usually don't do that much harm. I have several of "The great tit (Parus major)" in my garden, blackbirds and other birds, robins, etc. and others, and insects flying around too now, so I'll leave it to nature. A strong spray from the hose helps too. https://upload.wikimedia.org/wikipe..._tit_side-on.jpg/1024px-Great_tit_side-on.jpg
@AlainK , I normally do what you mention by water spraying them with a hose on the smaller maples. It's quite effective at making them go, although sometimes they are a bit sticky and need a bit help with a finger to remove them. On the bigger ones, I kind of ignore them, as those trees are strong enough. However, the more trees there are, the more time consuming it gets.. I understand the 'ignore' treatment :) A good tell tale signs of aphids infestations, is seeing ants going up the trunk to move them around. They're quite annoying really. Sometimes I do a spray with washing up liquid, but I have never found that too effective. The water spray method to blast them out of the tree seems more effective (although needs to be done regularly) This year surprisingly I've noticed more ladybugs than usual! Especially on a pine tree that has lots of small grey beasties. That's extra help from nature :)
Thought I would make a comment if that's OK Chris. I try all the methods that have been mentioned already. Especially encouraging nature. But last year the aphids were so bad I resorted to shop bought bug killer. And I have to say it worked overnight. Not advocating chemicals at all, but sometimes it has to be used, especially on small potted fragile grafts.
Derek, given the size of the pot (the new one is bigger), would you recommend adding more horticultural grit to the mix (I know there's more in the John Iness no 3 than no 2, but it still doesn't seem that much)? I would think I should I would be happy to have a backup plan in case it gets really bad! Are there a few that you know work and those who don't work? I saw recently a video on youtube from a Maple enthusiast, and he said he used one (let's just describe it as being a in a red spray bottle (to not give any name, if it's not allowed or if frowned upon?), and said that it work really well as well
For now, take a 12" spike (30 cm) and drive several holes into the top of the root system. This will add oxygen and allow the moisture to flow deeper and quicker into the root system. That will allow it to be just fine in that pot for another season. On the other hand you can simply place into a slightly larger / deeper pot and add your new soil and just leave all of the roots intact. Do not try loosening or breaking up the root system now that the tree is actively growing again.
