Keeping plant in same pot by trimming its roots

wild flower

I have an aucuba japonica in a VERY large pot for almost 2 decades now. (It would be hard to get a larger pot and there is no room for it in my garden, i.e. in the ground). In this time I have twice tipped it out and replenished the soil, whilst trimming down its roots (by about 33% the last time i.e. leaving 66% in tact.) 

However, despite giving it ericaceous feed (reasonably regularly), many (not all) of its leaves are noticeably much more lighter/yellow i.e. not the characteristic dark green with spots.  It is in the same position which gets the sun in the morning.

Is there a limit to how often the roots can be trimmed back in this way?  What should I do to address the lighter yellow leaf issue or is this not a problem?

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raisingirl

I don't know how old the oldest Bonsai trees are but it's much more than 20 years. I've got a beech tree that's been in a pot for about 30 years now. It's about 18 inches tall. So no, I don't think there is an 'in principle time limit. But there is some technique to it - pruning roots much as you do branches, rather than just an all over trim. And keeping the top growth 'in balance' with the roots. not all plants will put up with so much interference, though. I've no idea if aucubas are one that won't stand for it.

I'd be inclined to up it's food, for a start. Yellowing is most often starvation.

wild flower

Thanks for your replies.  I don't give the roots an 'all over trim' so much as a little from the sides but mostly trimming off 33% from the base of the roots.

Yes I have read about yellowing leaves = starvation but, since I give this plant reasonably regular (e.g. every 3 weeks or so) ericaceous diluted feed, I am hesitant that this is the problem - unless I need to step this up?

It's not really a huge problem, i.e. for the most part the plant looks healthy (with its characteristic dark green variegated leaves) and is not wilting in any way but there are too many outer yellow leaves that are making me wonder....I just want to see it in maximum health...(ha! unlike myself...don't get me started!)

Borderline

Why not post a photo. It is possible that some of these yellowing leaves are wilting and need pruning off. This action may rejuvenate your shrub. Are they along the base of the shrub? Some evergreen shrubs still have a cycle of old leaves coming to the end of its life and they tend to look worse for wear.

What sort of soil are you growing them in. It should be in a loam based compost and preferably away from harsh sun. A common problem - leaves turning paler in high sun.

wild flower

As mentioned, the plant is not wilting i.e. the yellow leaves so would they still need pruning?  Also, I mentioned it catches the morning sun i.e. not by midday.

I doubt that it's the soil since this is a recent problem and they have grown in the same soil satisfactorily for a very long time!

I hoped to solve this without taking a photo (which is a faff for me, i.e. not straight forward to transfer online).

Mark56

It's probably just shedding it's older leaves, mine does the same in Spring with yellow(er) leaves - especially noticeable after a harsh winter like the one we've had. They will tolerate quite a lot of shade. If concerned sprinkle some Fish, Blood & Bone and tickle it in to the soil surface then mulch or opt for a watered down liquid seaweed feed. 

wild flower

Thanks Mark - that didn't occur to me!