It will be near impossible to remove some species of trees from smart pots without cutting them in some way because fine root tips embed into the fabric. I suppose you could run your hand down the perimeter of the pot and break them that way but disconnecting the pot from the bottom of the rootball will still be a challenge.

The next generation should be one with a zipper or fastener to make it re-usable.

The one nice thing about the Rootmaker plastic pots is that they're reusable, but it seems the trappers & also smartpots do a better job overall, both in the rootpruning & temperature/moisture management.

BTW- I think I've seen you post about Smartpots before.

Have you found that they don't work as well for trees with either very coarse or very fine-textured roots?

I've put oaks, maples and pawpaws in smart pots. The oaks and maples both made dense fibrous root systems but the paw paw went ahead and made a big think taproot at the bottom and then turned sideways when it reached the bottom. The potting soil I used may have been partly to blame since it was too moisture retentive near the bottom of the pot and may have encouraged more root development for that species down there. I used the same kind of soil mix for all three types of trees, though. I think I have a hickory in one at home but I can't remember for certain. I'll check when I get home.

Interesting. I didn't realize Pawpaw taproots were that stubborn.

Do you elevate the pots or sit them right on the ground?

They were on a row of lumber. Out of the all the different pots I tried, those 6" net pots were the only ones that didn't allow taproot formation on the pawpaws. It also kept the plant quite a bit smaller compared to the other larger pots, too. I actually planted the last two pawpaws I had left a couple days ago. They had been in 2-3 gallon containers for two years. They didn't make huge taproots and the large roots that did form at the bottom were easily spread out. So it seems this was an acceptable temporary storage container for them. I think the smart pot actually had the largest taproot of all the ones I examined lol

Hair,
I reuse all my various versions of Smart Pots. It's work to get plants out without destroying them or the pot, but can be done. What I have found that works best is not to over stuff the pot to begin with, and then when it's time for removal, roll the top back down the outsides. Don't make a roll, but more invert it from the top down. You will have to push up from the bottom the root ball, while pulling on the sides, working your way around. I've only lost one doing this. I also suggest you cut some small maybe one inch drain slots around the base for excess moisture to escape. I lost a plant or two before I realized that this can hold too much moisture for some species. After I started making these cuts, I have had not further problems.

Arktrees

Here are the various species I have obtained seed for (or have ordered):

Quercus coccinea
Quercus michauxii
Metasequoia glyptostroboides
Taxodium distichum (northern provenance)
Aesculus flava (aka octandra)
Acer nigrum
Acer japonicum
Acer palmatum
Cedrus libani
Abies hollophylla

As it is I will probably have too many trees growing - wife is already getting concerned...haha.

Honestly, I probably can only keep 1 or 2 of each species - the rest I'll probably give to a relative with 20 acres and not too many trees on it. He's always up for free stuff including plants.

Welcome to the "growing from seed" addiction! IMO, planting plants you've raised from seed and sharing the extras is every bit as rewarding as planting some 10 gallon beauty you snagged at the local nursery =)

I have tried folding the pots down as Arktrees has instructed above but I lack the upper body strength to pull it off lol

I actually decided to start the Q. michauxii inside under grow lights in Rootmaker 18-cell propagators. The farthest along have about 2" of top growth. Some have just started to push upward but all have roots & have airpruned out the bottom of the pots.

The coccineas, maples, and the Aesculus are in the fridge stratifying. The instructions from Sheffield's said 60 days IIRC for the Scarlet Oaks as well as the Buckeyes. The maples were 90-120 days.

Will they start just pushing roots at that point where stratification is "done"?

The conifers are on their way from F.W. Schumacher, should have them any day now.

Once they outgrow the rootmaker cells, I'm going to try out both the Rootmaker pots/Roottrappers as well as Smart Pots to up-pot them to. I'll probably do some "regular" pots too. Smart Pots seem to be much more widely available (Rootmaker seems to sell basically direct plus about 3 other companies) & a bit cheaper.

Did you grow exclusively outdoors, or start indoors or a greenhouse?

Did you plant right in 1gallon smartpots or start them in a smaller container to get the taproot under control first?

One other question - do the smartpots still root-prune on the bottom when the bottom touches the ground? Since all literature says it airprunes vs. "constriction" or other methods, I'd think that if it sits on the ground, the roots will just go through the fabric, and keep going into the dirt without pruning.

To answer your last question first, roots will grow out of the bottom but IME they do not add caliper as quickly as they would had they grown directly into the soil without the fabric barrier which inherently has predetermined small openings that might help constrict root thickness.

I started all of my previous seed batches in 6" net pots from farmtech. These also air prune but if they are left on the ground or any solid object, the taproots will keep on growing twisting and thickening as they see fit which makes removal from the net pots without causing harm to the roots exceedingly difficult. After a half to one season in the net pot, I moved the seedlings I wanted to keep up to 3-5 gallon smartpots and smooth sided plastic containers to compare the effects each had on the root systems within a year.

This year, I'm doing it totally different just for variety's sake. I have direct sowed seed into a seedbed and will pot some of them up in late spring/early summer. After the first growing season I will remove them from the pots and dig up some of the ones left in the ground and compare just for kicks. I will then plant both and see how they fair being grown and transplanted from different methods. All just to satisfy my curiosity. I do plan on shovel pruning the taproots on the oaks and hickories I leave in ground midway through the growing season. Possibly multiple times. I'm sure I'll post a topic asking for help when the time comes =)

Sounds like a neat experiment!

You can reuse bags with heavy duty staplers after you cut it.

I've done both smart pots and roottrappers. I much prefer roottrappers because of hot weather in Texas. Smart Pots seem to dry out very fast! The roots would escape through the seam at the bottom and grow into the ground which was great for anchoring the tree in case of heavy winds. Not to mention extra water and nutrients. Since the roots are constricted at the seams, they are easy to break off when harvested.

So it sounds like Smart Pots work by both air pruning AND constriction.

Re: Smart Pots - do you typically see small roots poking outside the fabric? How do you know when it's time to pot up to a larger size?

Roottrappers apparently work by "root tip trapping". It works as we've seen, but I actually have one of the 5" white roottrapper bags at home (haven't used it yet but will this year) and lookuing at it, the inside is basically just a fabric like you'd see in a thick blanket - it's hard to imagine how it works (but obviously it does)!

It also appears that they would drain water VERY slowly when watered.

There is another roottrapper product with knit at the bottom for better drainage plus more roots to anchor into the ground.

Roots don't come out on the sides of smart pots but you may see fine roots at the bottom. I don't know. It's been a long time since I last used it. When to pot up? Probably will have to go to smart pot website for some info. It should be there. It probably depends on the size of container being potted into larger size.

I have had some nearby plants in 6" net pot containers, most significantly clethra alnifolia 'Ruby Spice', root into smart pots as well!

You mean where the pots touched, the roots went out the net pot and into the neighboring smart pot from the outside?

Lou - if you don't see roots coming out of the Smart Pots, then how are they root-pruning?

"You mean where the pots touched, the roots went out the side of the net pot and into the side of the neighboring smart pot from the outside?

Exactly! That little Ruby Spice had quite an aggressive root system

One important thing to mention - If you are air-pruning seedlings that are particularly stubbornly tap-rooted, try root pruning at a much younger age. With some types of trees (It has worked really well on White Oaks and Buckeyes), it is good to start the seeds in a solid-sided, mesh bottomed flat (1/4 inch mesh, at least - Has to be big enough for the root to grow through), and keep them off the ground. The roots prune at 1 or 2 inches, and branch out vigorously. Starting straight off in a gallon pot is a bit of a no-no, as by the time the taproot reaches the bottom, most of the root has become woody and will not sprout secondary roots. The more tap-rooted a species is, the earlier you have to root-prune.

Hope that helps your project! I for one prefer the white laminated roottrappers, as they don't dry out as quick as the smart pots.

Arktrees - you mentioned growing some Scarlet Oak from seed. Did you grow those in Smart pots?

As far as adding caliper - I've read reports that are all over the map - suggesting that oaks, in particular, might actually caliper a bit faster than in the field, whereas other species languish a bit even if the rootball ultimately makes for better transplanting into its permanent location.

I would imagine caliper growth goes like this:

Field Grown > Root pruning pots > traditional containers

Hair,
I started them in the small 6" net pots that John has spoken about, but then moved them to Smart Pots a couple months in. Have don the same with White Oak, even leaving White Oak in the net pots for the first year, then transplanting in winter. They were fine and ready to hit the ground in the fall. BTW, Scarlet Oak is one that caused me to put the small cuts around the bottom to improved drainage at the very bottom. Have not had an issue since beginning that practice.Also unless the roots are really large growing out the bottom, I have simply pruned off the excess, and have had no issues. Blackgum is the only one that I have had a circling taproot in the fabric root pruning pots (not that I have grown EVERYTHING in them). Those I pruned the taproot back (there were plenty of other roots), but did not in any way completely remove the taproot. Those trees were none the worse for it. Acted like nothing had ever happened.

Arktrees

Good info since I'm growing some Scarlets this year!

IME Scarlet Oak prefers a soil moisture level which most plants would be almost too dry in.

I think perhaps if the root is too thick in diameter, that it can't fit through the fibers & instead will circle. Hence your issue w/blackgum & John's issues with the Pawpaws. Pecans might do the same thing since they also have a thick taproot.

What kinds of potting mixes are you using?

One other question - for oaks and other nut trees, IME the nut stays attached to the seedling most if not all of the first season.

What do you do to keep squirrels and other annoying creatures from digging up the tree to try to get to the nut?

Hair,

I use Al's 5-1-1 mix (pine bark fines, peatmoss and turface, expanded shale, zeolite, sharp sand, etc.

All the information is at container forum. Well draining media is the key.

Check this out:

I wonder if the overlapping nature reduces the effectiveness.

Here is a link that might be useful: Smart Pot Transplanter

Hair,

Only if Smart Pot would cover it with white stuff...

I just stored 4 containers of Montezuma Cypress seeds on wet paper towels from 4 different trees. Sentido cultivar has rather small seeds. I'm curious to see what I'd come up with seeds from BC-MC hybrid T-502 that was bred from China. My 502 is still retaining its brownish red foliage at the moment. Pretty late, huh?

Lou...where did you get that 502 hybrid? I thought it wasn't available to the public yet.

I got it from Dr. Creech at Stephen F Austin State University. I also have 27, 405, 406, and 407.

Here is a link that might be useful: Hybrids at SFA campus

Question for those who have used them - do the roottrappers and smart pots (those two in particular) work for "thicker" or fleshier rooted species like Aesculus?

I'd worry that the thick roots won't fit through the fabric, and instead of being trapped/airpruned, would just circle.

I got some first-hand evidence of how the Smart Pots seem to work. I had transplanted a Quercus michauxii seedling around April 1 into a Smart Pot. It was bitten off by a critter this weekend, so I decided (since I have more michauxii seedlings than I need anyway) to just sacrifice it, and dump and check out the root system.

There was one long, slightly "thick" root going down at an angle off the air-pruned tip of the taproot that had reached the bottom and worked its way into the fibers. The root had not emerged from the outside of the pot, but instead seems to have gotten "stuck" there. No side roots had branched off of this particular root yet, but I imagine that the Smart Pot works both by airpruning AND 'trapping' of the root tip.