Hi everyone, I have a few JM’s to repot and will need to root prune over the years. Wondering if it’s a good idea to use a plastic or metal pot liner (nursery pot) or what I’ve recently seen a “grow bag” to line a decorative pot so that it may be easier to remove the tree from the pot and root prune? Some of my JM have clay decorative pots and the trees stand roughly 5-6’ so pruning can be heavy work considering I’m only 5’2”. Does anyone have any thoughts or experience with the “grow bags”?
My concerns would be maintaining aeration and drainage of the compost. Both are very important with maples.
Good morning Lisa, I've added @Xi-feng to this as she is growing her maples in growing bags/ pots. Might be some good advice woman to woman so to speak. I think it is sometimes easier to physically comprehend moving pots around from someone of the same sex and the methods used. But a footnote from me. I agree with J @Jaybee63, aeration and drainage must be the priority.
Hey @Acerholic what about an aluminum sleeve in a decorative clay pot? I work with lots of metals so easy for me to get.
The only thing with metals Lisa is that they can bake the roots in a hot Summer. I prefer pots that reflect the heat. But a decorative glazed outer pot sounds good.
Hi Lisa A quality clay pot or cement pot or cedar box is best. They will all insulate and protect the roots. Cement is best due to its cooling insulation in the hot summer heat. Maples do not like wet feet, the water needs to move thru the pot. Re - potting is quick and easy with container grown specimens as they always pop out like a plug when container grown right from the start. I will be posting a re - potting video in the next few days as I have an "ozakazuki" that is due for re potting. As others have said, using plastic or metal and honestly, even those grow bags are all not beneficial for your japanese maple.
Thanks so much @Otto Bjornson , you see the picture that is my avatar that JM I need to put into that pot currently it is sitting inside it in it’s original nursery pot from last year. I was fearful the pot shape will make future root pruning a nightmare. I think @Jaybee63 is correct the soil is exhausted, I knew to repot it in early spring. I didn’t repot it when I received it cause it’s soil seemed perfect and the tree seemed very happy frankly I didn’t want to screw it up. It’s been in that spot for a year and I think it is good in that location, I believe I can up pot it now from the nursery pot to the clay one it’s sitting in.
I’m completely in agreement and firmly believe in breathable terracotta or clay pots and nearly all my Maples that are not planted are in such pots. This ensures the compost dries out between watering.
@Lisa Harry My approach when it comes to re-potting and you are not sure if it is ready to be re-potted, my rule of thumb is : If you grab hold of the main stock and can slightly lift the tree? then tap the pot and if the tree wants to pop out, it will, like a solid plug. On the other hand if you grab hold of the main stock and the tree wants to lift without any of the soil moving around the edges.. then it is not ready to re-pot. Also, if you want to keep it in that pot for another year just get yourself a 12" ( 30cm) spike / nail and drive about 20 holes into the top soil surface. Sprinkle with a tablespoon of slow release fertilizer as well That will aid in allowing moisture to flow down and will give you another year to decide what to do
I've only had my littlest trees in grow bags for a while. but I'm really impressed at how the water just pours out from the sides and bottom almost immediately after watering, which seems great in terms of drainage. I have the bags lifted up a few cm above my patio floor so they're never sitting in damp, and I hope that will help with keeping the bags themselves from deteriorating too quickly (and they weigh almost nothing, so that's definitely a bonus!) Time will tell how well it works, but hopeful so far!
A few years ago I made some bags out of thin landscaping fabric, a bit smaller than the size of pot I was using so that they sit inside the pot nicely. I didn't repot these trees for 6 or 7 years at a guess and am now working my way through them this spring - all have been healthy despite not being repotted for so long. One thing I would advise (that I stupidly did not do) is to take the bags out of the pot at least once per year and remove any debris that has collected between the side of the bag and the pot. If you just leave them in situ like I did the roots go through the bag and into the soil that collects under the bag and between the bag and the side of the pot causing a big headache when it is time to repot. I had a Katsura in a bag inside a large plastic pot and there were over a hundred full-size dead snail shells jammed between the bag and the wall of the pot where they had become trapped and unable to escape, not to mention about fifty that were still alive! So, if I ever do the bag thing again I will follow my own advice and clean the pots out every year and not leave them in the same bag for more than three years or so. The two reasons I am not using bags this year is that I would need bigger pots than to repot without bags, and that it is time consuming to make the bags. One bonus is that if the bag is the right size smaller than the container it is in, when it comes to repot the maple it can go back into the same container without the bag and you have up-potted it without having to buy a bigger pot!
@maf thanks so much for sharing your experience with me this is all very helpful. Good luck with the rest of your tree work this season
This is what happens if you let leaves and other debris collect in between the bag and the pot. It composts down to a nice growing medium and provides a secondary rooting zone for the maple and a headache for me: If there is just air at the sides of the pot the roots will stay in their own side of the bag. As you can see from the picture of this 'Filigree' after repotting it was very healthy after many years in that breathable bag:
Awesome thanks for the pictures @maf would you consider the bags for very long term? Like say a 6’ tree and keeping it that way. I ask just cause if I give the pot I like It will be challenging to move the pot and tree for root pruning thx
Yes, I think they are great for long term root health. You get a lot less root circling than in pots because the tips push through the bag and are air pruned. In fact I think I might use bags for some of my largest container maples this year. I found some half decent plastic tubs, 50 cm wide with almost straight sides so very wide base, bags would go great in them.
Hi @Acerholic @maf @Xi-feng @Otto Bjornson thanks so much all of you for your suggestions I did get a hold of a grow bag that gave ample room to my waterfall JM. I also redid the area it sits to a river rock bed. When I lifted the pot from the ground it had rooted through the drain holes into the slip pot I had it sitting in, started to circle that space about a s inch the into the ground. I had to trim the roots out of the holes to pull the pot out. I did no other root disturbance. I mixed the soil as per @Luke’s Maples suggestion and placed it back in its spot. I have it sitting on some wood until I can make a pot lifter at work. The 20 gallon bag was very easy to handle as it had handles I watered in place and added soil when it settled more. I really hope it works with these bags I feel the maple will be much happier. I’ll keep you posted thanks again Sorry could do pics or a video had a ton of work to do in the yard.
What a fantastic job you have done there Lisa and the very little root disturbance on a tree that size will do it no harm at all at this time of the year. I do like the way it still has protection by the fence from any prevailing wind, something to consider as it grows further. I hope you will also post a photo in a few months time when that corner of your garden will look like it's on fire ? 'Well done'. D
Lisa, that looks beautiful - what a gorgeous tree! You must be thrilled, and I'm glad the grow bag is working out - please do continue to post pictures through the year, as D said!!
Thanks @Acerholic it really does go an incredible colour in fall, fire is a great description. The wind is an issue where I am even though it has a fence the trees in my front yard which is what your looking at, are 5 feet from it and they are subject to a steady amount of wind. The way my house is situated I get a strong breeze in the front and bit more mild breeze in the back. (hence why I had to move “the rescue tree” last year). The wind is a hard one for me it’s intense so I mist my trees in warm weather. Hi @Margot it was staked when I got it last year from the nursery but it’s actually broken at the root and I’ve never removed it, I guess I should cause it’s not offering much service. @Xi-feng the bags are actually pretty cool to physically manage so far. This tree grew very vigorously since I got it last year because it had just been repotted a couple months before I got it but it is very root bound and has been for a while. I can see it has been struggling with its colour and look but I’m believing that this new pot even though not root pruned will really help it. I’m quite excited to see how it performs. Thanks everyone for your support
