How to change potting mix WITHOUT up-sizing pot? (forum)

Db starts with ...
This may sound bit silly question but I would like to know how to change potting mix WITHOUT up-sizing pot? Should I replace 100% of existing potting mix or just some part? How to remove existing potting mix without damaging roots and without harming plant? Once I take out plant from its pot, is it ok the place root ball in water (or use hose) to remove existing potting mix?

Lots of my fruit trees are currently in 40cm pot, potting mix seems to be collapsing and is not holding water for long as it used to be, so it needs to be changed, but I don't want to up-size pot as all plants are still very small..

Any advice?

Time: 5th November 2012 9:58am

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Phil@Tyalgum says...
Some of the TV presenters have demonstrated removing the top few inches of soil every couple of years and replacing it with fresh mix. A lot of trees in orangeries in Europe have been in the same pots for hundreds of years and they do a similar thing - you might see it demonstrated on youtube. I wouldn't take the whole plant out as it is a major disturbance to the tree, the surface roots are normally feeders only and regrow easily, while damaging the deeper anchor roots risks setting the plant back or killing it. Water the pot thoroughly beforehand as damp soil is easier to remove than the dry crust which often forms on the top.

Time: 5th November 2012 10:29am

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About the Author TyalgumPhil
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BJ says...
If slumping of your potting mix is a problem make sure they are raised off the ground a little. Worms can get into your pots and quickly turn a decent potting mix into a heavy compost, which compresses down to half the mass and many plants find hard to put decent roots into.

Time: 5th November 2012 11:03am

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Db says...
Thanks Phil.. In that case I don't need to change lot of potting mix in my pots..

Time: 5th November 2012 11:57am

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Db says...
BJ, looks like that's my problem, I haven't seen worms but many times I have seen ants going inside of pot from drainage holes and bit of crushed mix coming out of pot from these holes... most of my pots are sitting on gravels in my garden.. How can i avoid ants going in?

Time: 5th November 2012 12:01pm

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MaryT says...
Good advice from BJ and Phil but I'll add my two bob's worth in addition to what's said above. Do not hose off the soil around the root ball; keep it compact by watering well as Phil said so they adhere to the roots.

When you re pot a plant you do need to pack down hard the new mix that's below and around the plant. Make sure the original level of the plant is level with the top or slightly above the new pot as the mix will shrink.

If you trees are still small for their pots then I think you may have potting them up in the wrong size in the first place.

My pics shows a plant that's out grown its pot so I've potted it up and will use the pot it vacated for another plant when it outgrows its pot.
Pictures - Click to enlarge

Picture: 1
Picture: 2
Picture: 3
Picture: 4

Time: 5th November 2012 12:07pm

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Db says...
Thanks MaryT.. I think you are right, I might have potted in much bigger pot to start with... Great photos on explaining how to change potting mix when up-sizing pot.. But at the moment I don't want to upgrade pot size, so I'll be using existing pot.. And I want to change potting mix because issue is its not longer holding water for sufficient period as it used to be before because its structure is collapsed over the time... Soil level has been dropped over the time, so I can add couple of inches of new mix at bottom but I don't think that's sufficient to hold water for longer period..

Time: 5th November 2012 12:59pm

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MaryT says...
Sorry Db I didn't see your comment re ANTS before writing my blurb. That is another topic that you can find on this forum.

Time: 5th November 2012 12:59pm

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MaryT says...
You can try a liquid soil wetting agent to help the mix first then top up with a premium mix around the edge of the pot; taking care not to bury the stem of the plant. My pots are all too big for me to re pot now so I just top up with a rich organic mix as well.

Time: 5th November 2012 2:10pm

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Db says...
Thanks MaryT, don't be sorry, your post was useful, it is an reminder to me not to use bigger pots than required..

I might try liquid soil wetting agent, do you think they are really useful, I tried adding water crystal before but didn't liked it much...

Time: 5th November 2012 2:21pm

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MaryT says...
The one thing you did not mention is the health of the plants - if they are doing well, I'd say don't worry about it until they look like they need help. I'm a watchful gardener but a lazy one. Like that plant had roots hanging out of the bottom holes before I gave it a new home. :)

Another thing I want to add is that a mix that drains well is not necessarily bad; you don't want the plants to be waterlogged.

Time: 5th November 2012 2:58pm

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Db says...
MaryT, health of my plants is not that bad, some did grow very fast (like Panama berry, Acerola Cherry, Mexican cream guava) till start of this winter... Panama berry looks sick now and throwing lots of leaves, it has not started re-growing in this spring, but fruiting now... 2 Mango trees has not put on any growth in last 8 months but they flowered and have set fruit now (I removed flowers of Kwan but it re-flowered so I'll remove flower again once it set pea-size fruit)... Some other plants like Blueberry didn't grow at all in last 8 months but now started growing, same with black sapote... Cutting grown Pawpaw is not happy in pot (growing in 110L pot)... Figs are thriving though...

Most are not growing as fast as when I started them and other problem is pot is drying up quickly (now a days I'm watering them almost everyday or alternate day)... And potting mix level is dropped by 2 inches in almost all pots so I think it has become compact... So I was thinking to change potting mix... I think I'll just do some top up and try liq wetting agent that you suggested...

Time: 5th November 2012 4:26pm

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MaryT says...
Well I think you'll see a difference anyway in the next few months; it's the season. Plants in pots do need to be fed more often than those in the ground as well. Smaller amounts more often is the usual regime. I agree with removing small fruit if too many rather than removing flowers (that would only encourage more flowering). In any case trees do abort excess fruit all by themselves. Sounds like you don't have a huge problem there, Db. Good luck.

Time: 5th November 2012 5:00pm

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Db says...
Thanks MaryT.. What fertilizers do you use for your potted tree? I have B&B, DL, powerfeed, sulphate of potash, seasol, citrus fertilizer, Azalea and Camellia for acid loving plants.. I'm using powerfeed and seasol more often than the rest...

Time: 5th November 2012 5:07pm

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MaryT says...
I use similar to what you use; definitely slow release ones like Osmocote in the potting mix when first planted then every so often. I use DL and some B&B+potash with the spring growth, then increase fertiliser and watering after fruit drop/thinning. You just don't want too much nitrogen when they're fruiting. I also like seasol and other fishy fertilisers. In fact my plants like a variety of food, just like me :)

Time: 5th November 2012 6:09pm

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Julie says...
Db, have you seen any slaters? They will gradually chew away at the organic matter in the mix, leaving just sand. Then the water runs out of the holes they have made and doesn't absorb.

Just a thought - I have seen it often.

Time: 5th November 2012 8:51pm

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Db says...
I haven't seen slaters yet but after coming from work foday I saw one earthworm in black sapote's pot on it's top soil and it vanished in potting mix before I could pick it out, so you was right BJ, earthworm in the pot could be issue here. This pot is sitting on raised garden bed which has earthworms but more than half of my pots are on gravels so they may not have earthworms. How do I get rid of earthworms in pot?

Time: 5th November 2012 9:28pm

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Pauline says...
How long have they been in the potting mix and was it a decent quality one in the first place?

I repot every 2-3 years, using premium potting mix. I tend to water the pot, take the plant out and worry the roots with my fingers. Any that are curled around too much I prune off, and any manky looking ones. I do find most of the potting mix I loose is from the top area. They hold onto the mix more lower down. So you don't end up actually changing every bit of potting mix.
I use the new premium potting mix and Osmocote mixed in. Then I give the top of the plant a prune in line with what I have taken off of the roots.
Good luck. :-)

Time: 5th November 2012 9:37pm

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Db says...
Pauline, some are in pot since last 9 months, some planted only 5-6 months back.

Time: 6th November 2012 8:39am

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Pauline says...
They shouldn't need changing that soon if you used premium potting mix. The general ones really are not even worth looking at. Do you remember what type you used?

Time: 6th November 2012 5:57pm

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Julie says...
I thought that too, Pauline. I only repot when the roots get too big for the pot.

Time: 6th November 2012 9:12pm

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Db says...
Pauline, I used 50-50% mix of Searles premium potting mix and H40 potting mix that I buy from Centenary landscapes here (this mix has low slumpage rate due to more sand), I've have also added little bit of compost and peat moss dust (after wetting) in all pots. So overall quality is good I think. But still potting mix level has been dropped by 2-3 inches in almost all pots. So I was thinking to change potting mix.

Julie, I agree but roots of some tree are very vigorous, eg both of my mango trees has not put on any new growth at all but roots are outgrowing the pot, they started circulating in pot within 3 months of transferring from nursery 175mm pot to much larger 40cm pot.

Time: 7th November 2012 9:49am

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Brain says...
The issue with the sink rate of potting mix can be attributed to whether the mix was compressed at the time of planting, any potting mix being leeched out at the draining holes and whether organic matters are further broken down, reducing mass.

Almost all of my plants are in pots, so I can relate. If the potting mix is still holding moisture, then you probably don't need to replace the potting mix. What you simply do is to remove the plant from the pot, add some more potting mix to the base and done! Alternatively, add to the top along with some mulch.

I use pure searles premium potting mix exclusively. I've found some batches are better than others. So really you should check. I've found some mixes to be too woody and fungi sets in after a while and destroying the water holding capacity of the mix. Otherwise, I still have potting mixes in pots still going strong after the 2 year mark.

Time: 7th November 2012 4:29pm

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Db says...
Thanks Brain, I do compress mix at the time of planting but not very hard... Mix is getting leached out from drainage holes but in very minute quantity...
I can see ants on almost all pots, can they do this damage (breaking organic matter)? How to increase water holding capacity?

Looks like I don't need to change potting mix and just need add some mix at bottom..


Time: 7th November 2012 5:12pm

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peter 1000 says...
hi db
i would give your pots a good watering
then remove plant from pot to check
if the rootball has been completly saturated, if not place back in pot
a submerge the whole thing in a
bucket of water for a couple of hours.

i have just gotten rid of ants in
some of my pots using liquid
pyrethium from bunnings.

Time: 7th November 2012 8:44pm

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Db says...
Thanks Peter, i'll try both of your suggestion ie submerging in water and pyrethrum.

PS: With pyrethrum, do you mean to spray plant or add pyrethrum mixed water in the pot? Previously I used pyrethrum to spray on plant which removes ants but only for short period..

Time: 8th November 2012 9:12am

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Brain says...
I dare say, it would be pyrethrum mixed water, soak the whole pot in it and hopefully that will kill the ants.

My experiences with ants in pots are, their presence create air pockets in the potting mix (ditto for lack of soil compaction when repotting), causing it to dry out easily and once dried, it is next to impossible to get it hydrated again. Immercing the whole pot works to some extend but it is not a guarantee method. This is because there can still be dry patches and secondly, if the soil is past its use by date, then soaking only temporarily fix the problem.

I believe there is a whole thread dedicated to removing ants in pots and you may consider a read.

Adding organic matter like compost can aide water holding capacity. Or using water crystals.

based on the issues identified, you are faced with the same problems that most pot plant owners have. I.e. potting mix is getting dried out and less than optimal, roots getting out of control, ants in pots.

I'd agree with the previous poster to soak the pot in water first and see if the soil is still ok. If not, repotting is the only next alternative.

Time: 8th November 2012 10:38am

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BJ says...
I'd also suggest coconut fibre (coir peat) over otehr peat or sphagnum as it is renewable and from many reports of big container growers it rewets well and easily after drying out, whereas most other similar products can get a bit hydrophobic.

Time: 8th November 2012 10:46am

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Db says...
Brain and BJ, thanks a lot for your suggestions.

Time: 8th November 2012 11:31am

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