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
I wanted to add this here after seeing this knife on The Beechgrove garden this morning. I'm not advertising this company in any way and I have nothing to do with the company. But this tool could be very useful for those pot belly pots that so may people have. Pottery/ Container knife
For years we only grew and sold container grown specimens in our nursery. Rule of thumb, as others have mentioned, just go up to the next size pot as minimal space is all that is required. During the active growth cycle ( right now April / May ) do not disturb the roots at all. You will notice they are white and tender, leave them be! Just pop the tree out of the pot, add your new soil mix in the new pot with a little on the the bottom and then tuck in soil around the outside edges. Regarding soil mix, NO DIRT! Just composed bark mulch ( 80% and 20% sand mixture) as a general rule of thumb. Don't pack the soil mix too tight at all when re potting. Also a 6 month slow release fertilizer is great, we use a 16 - 10 -10 mix ( one tablespoon) each spring. Also the more common 14-14-14 is just fine. And remember only slow release
Clever, but a bit expensive for me. But clever. Excellent advice. When I have to do an "emergency repot", I use a very free-draining mix, at least 50% of pozzolane (lava rock) and composted pine bark. I also add a little fertilizer, but only 6-6-6 because I don't want too much nitrogen, so the tree doesn't grow too fast.
Fert numbers are a density. Half as much 12-12-12 is exactly the same. IOW, 1 gram 12-12-12 is the same as 2 grams of 6-6-6.
Agreed Alain , a silly price. But to help with all those stupid shaped pots is a step in the right direction. I am sure someone else will produce one that is a lot cheaper.
Right-o. In garden centres here, I find 6-6-6 as slow-release ferts, but I also use liquid 3-3-3 from supermarkets, it's very cheap. When I use it, I just double the dose. The "Walter Pall" way...
