Hi If a tree is currently in a pot 30cm (H) x 30cm (W) (18 litres) what increase in size would you go for when repotting? Thanks!
@Mani good evening Mani, the very next size up. It is too easy to pot up in too large a pot, but this should be avoided. Maple roots in pots are happier when they are snug. 20 Litre max.
To me, repotting means pruning the roots, and pruning some of the branches too. I prefer to do it in late winter, early spring, before budbreak.
I should have added that after repotting, a tree should be kept frost-free. Outside as long as it can, but to be brought to a protected place when need be. This may seem evident, but it's better to say it again ;°)
@AlainK I had assumed that would be the case! So, sometimes you might not increase the size of the pot just replenish some of the soil?
A slightly larger pot is the rule for a "patio tree". Using the same pot is what you can do with some bonsai. It's basically the same process, but it depends on what you want to achieve.
@AlainK I had a few more questions! How much of the roots do you take off? Why do you do this? I thought energy is stored in their roots therefore pruning the roots will weaken the tree? Thanks M
@Mani that is always the temptation, but IMO the answer to that Mani is NO. Maples do like their roots snug in pots.
So, down to the practical issues now........do you take your potted acer out of the pot first to see if its roots require more room? If the roots are not packed into the current pot will you not repot at all?
Hi Mani, hope you are well, I check underneath my pots to see if the roots are making their way out of the bottom. I also gently scrape away a little of the surface substrate to see if the roots are right at the edge. If they are, then a repot is the order of the day. I also keep a diary of when I repot a particular maple as then I know roughly when I need to trim roots and give some nice fresh medium. If I go up a pot size it is always only to the very next size up. Maples do like to be snug. Hope thats of some help.
Some very helpful comments above.. Just to add my thoughts..An increase in pot size of 2ltr would give you only 1cm of additional space all round..for me this is too small even if you do root prune..they will grow back with vengeance. I repot every couple of years so I step up the size a bit more..for me I go up 5, 10, 20, 30, 40, 60, 80, 120, 160 that gives you a few inches growth space all round but not excessively..
Thanks for the tips! Interesting! I think I will try this too! As some buds are forming now, is now the time to repot? Just making doubly sure! Thanks!
I do mine at the beginning of March Mani, before they start to leaf out. Some do it in Autumn, but this takes you into cold weather and the roots are less likely to progress fast, than in warming conditions. I'm 60 miles South of you, so the timing is about the same.
I’d leave it for a couple of weeks if it were me as D says it’s been freezing over recent weeks, even pots 30” across were frozen hard in my garden. When you are in arms reach of spring any damage from root pruning will spring back with vengeance, but right now I’d say there is a risk of infection. I might slip pot a few things right now but not root prune
