Methods For Growing Lots Of Trees In A Small Footprint For Cost-Effective Silvopasture Establishment

[Casey Pfeifer]

I thought I'd share my current methods using air pruning beds to grow various livestock fodder trees for silvopasture establishment in hopes that some other folks in this network are doing the same.

My goals are to grow 1) healthy, well-structured trees that 2) can be harvested with intact root systems for maximum survivability during establishment 3) very little expense and ongoing management cost throughout the year for me (the grower).

I've been growing trees in air pruning beds for years now, and have just moved to Tennessee and am reconstituting my nursery here - building air pruning beds using mostly scrap lumber, repurposed shade cloth etc.

The air pruning beds I'm building now are still in the same basic style as the ones detailed in this video from a few years ago from when I was in CA (based on the work of Dr. Carl Whitcomb). Below are some photos of the beds - just simple frames with a 1/2" hardware cloth mesh fence stapled onto the bottom, overlain with old shade cloth to retain soil while also permitting roots to penetrate through and air prune. Beds are protected here by a single layer of 3/4"x1" x 7' wide deer fence over bamboo stakes. Growing medium is currently about a 3:1 mix of double ground red oak bark and mushroom compost. I've been making charcoal and will add some biochar to the mix once I get the charcoal crushed, inoculated and charged with nutrient.

Trees currently started from seed: Black Locust, Thornless Honey Locust, Siberian Pea Shrub, Leucaena, Paulownia, White Poplar, River Birch (we arrived in late May and missed a lot of the spring season, so I am starting whatever I can reasonable force-germinate now - other things requiring longer stratification will get started at the end of this year in cycle with the seasons).

Trees started from cuttings: Weeping willow, red mulberry and Austree Hybrid Willow. (basically whatever I can find around me that fits the livestock fodder tree category).Caragana arborescens) emerging.

Leucaena/White Lead Tree (Leucaena leucocephala) and Thornless Honey Locust (Gleditsia triacanthos inermis). Short beds were a mistake - the dog and the cat really seem to want to lay on these things.

Underside of one of the beds - 1/2" hardware cloth fence stapled on top of the 2x4" frame, with recycled shade cloth lain on top of that to retain soil while permitting air pruning of developing root tips.

For the Austree Hybrid Willow I hurriedly put in a "willow paddie" - basically I de-sodded the lawn adjacent the farmhouse we're in, made planting mounds, and planted a bunch of 15" long willow cuttings in the narrow trench by laying them down horizontally to maximize shoot production for making future cuttings. Installed and plumbed roof gutters to a downspout and into the paddie. Thus far it seems to be working well - the willows have been in the ground a bit less than a month as of 7/17/23.

The "willow paddie" - I'm hopeful that the cardboard sheet mulching, mulching with red oak, and the frequent inundation with lots of roof water will help to keep weed pressure down. More to come as this progresses!

For anyone else growing trees in nursery settings I'd love to see and hear what ya'll are doing!

With Gratitude,

- Casey

[Scott O'Bar]

Cool. What part of Tennessee is this?

I'm familiar with the concept of air-pruning pots. I do believe they are effective in what they claim to be able to do, although I have no experience myself.

Does anyone know what happens to tree species that inherently create deep "sinker" taproots when they are transplanted from such pots?

I have experience in Southern California with drought-tolerant species as Mesquite and some african natives, as well as Carob. With Carob, for example, it is definitely not recommended to grow in a traditional pot first due to root complications involving the sinker taproot. My understanding is that an air-pruning pot prevents any one root from becoming dominant, and instead creates a sort of net-like root structure. I wonder if such tap-rooted species would be able to re-establish their dominant taproot structure once transplanted from an air-pruning pot.

As far as your design, how does it prevent lateral movement of the roots? I assume each seedling's root system would become entangled with its neighbors in those beds, unless you're pricking them out early while they are still very small.

[Casey Pfeifer]

Hi Scott,

I'm in Pikeville, TN - north end of the Sequatchie Valley - eastern TN.

The tap roots get air-pruned just like any other root, however its not as if the root is forever halted at that length. With air pruning, the root tip dessicates, and this back propagates the signal back up the root for ~ 4" to increase lateral branching as a means of finding a way around the obstacle (in this case air).

Once an air-pruned tree is replanted, ALL of those dormant air-pruned tips resume growing from apical buds - and because they haven't been cut or shorn off (i.e. ball and burlap) they are much less susceptible to disease. So if the species of tree you are growing is a "tap rooted" variety (which most are when they are young, at least) the sinker roots will resume growing as they would have, only now with a much increased mass of feeder root tips above them.

If you'd like to learn more about air pruning and how it influences root branching, including growth of formerly dormant tips after the trees are planted, I'd recommend starting with this video by Dr. Carl Whitcomb: https://youtu.be/LdGzn8kbULc

If you want to go more in depth, he has an hour long video on similar topics as well: https://youtu.be/_lkDLSPWZd0?list=RDCMUCfyN7moqhBJbILGTjPVv42g&...

My design doesn't prevent lateral root movement, but the trees are very easy to tease apart after 1 year in the beds - I documented the process in this video: https://youtu.be/sza2c9UpEf0

I did experiment with carob one year in the air-pruning beds - I didn't have great success with germination, and they grew very slowly, so don't have much direct experience to offer there.

Are you the same Scott O'Bar that wrote Alternative Crops For Drylands? If so, THANK YOU. That book is awesome and I've used it so many times as a great resource over the years for some of the designs we did in CA.

[Robbie Coville]

Great to see! A quick response from a Mid-Atlantic perspective: many folks in NY and PA are growing trees this way successfully. I have 2x1' air prune beds made from scrap wood that have lasted years (surprisingly), that size makes them more manageable to move if needed, though even that amount of soil is very heavy. They work great and though I get some seedling losses around the edges, uprooting seedlings and sorting them is pretty easy work with those beds and a soil knife. Most of the air prune beds I see are similar to (or based on) Edible Acres videos on YouTube about air prune beds and how to cap them to protect seedlings.

Growing willows that way sounds great too. I have a different system but same idea, and the extra irrigation has resulted in far more growth than in other willow plantings started at the same time.

There's a big need for more nursery stock tailored for agroforestry uses - thanks for your efforts!

[Scott O'Bar]

I didn't know the mechanism of action for those air-prune pots. Thanks for sharing. I will watch those videos too. Nowadays, I'm more interested in direct-sowing seeds as I believe that they are better off by being able to develop their default root structure, not to mention avoiding the trauma that can be transplanting. You make a good argument for those air-prune pots though as I could see how it would be a big advantage to have a larger network of feeder roots.

Yes, Alternative Crops for Drylands is my book. I'm curious that you live in TN, but did work in California. Are you a landscape architect or something along those lines?

Casey Pfeifer said:

Hi Scott,

I'm in Pikeville, TN - north end of the Sequatchie Valley - eastern TN.

The tap roots get air-pruned just like any other root, however its not as if the root is forever halted at that length. With air pruning, the root tip dessicates, and this back propagates the signal back up the root for ~ 4" to increase lateral branching as a means of finding a way around the obstacle (in this case air).

Once an air-pruned tree is replanted, ALL of those dormant air-pruned tips resume growing from apical buds - and because they haven't been cut or shorn off (i.e. ball and burlap) they are much less susceptible to disease. So if the species of tree you are growing is a "tap rooted" variety (which most are when they are young, at least) the sinker roots will resume growing as they would have, only now with a much increased mass of feeder root tips above them.

If you'd like to learn more about air pruning and how it influences root branching, including growth of formerly dormant tips after the trees are planted, I'd recommend starting with this video by Dr. Carl Whitcomb: https://youtu.be/LdGzn8kbULc

If you want to go more in depth, he has an hour long video on similar topics as well: https://youtu.be/_lkDLSPWZd0?list=RDCMUCfyN7moqhBJbILGTjPVv42g&...

My design doesn't prevent lateral root movement, but the trees are very easy to tease apart after 1 year in the beds - I documented the process in this video: https://youtu.be/sza2c9UpEf0

I did experiment with carob one year in the air-pruning beds - I didn't have great success with germination, and they grew very slowly, so don't have much direct experience to offer there.

Are you the same Scott O'Bar that wrote Alternative Crops For Drylands? If so, THANK YOU. That book is awesome and I've used it so many times as a great resource over the years for some of the designs we did in CA.

[Casey Pfeifer]

Yes, direct sowing would be my ideal as well - air pruning feels like a next best option, and miles better than mainstream nursery practices.

You did an amazing job with that book - thank you again for creating it!

I'm a CA native by birth, just recently moved to TN for more freedom to do the things we want to do with our lives. I'm not a landscape architect - just a self-taught type. I got hired to do my first property design back in 2015 and have pretty much been doing them ever since.

Scott O'Bar said:

I didn't know the mechanism of action for those air-prune pots. Thanks for sharing. I will watch those videos too. Nowadays, I'm more interested in direct-sowing seeds as I believe that they are better off by being able to develop their default root structure, not to mention avoiding the trauma that can be transplanting. You make a good argument for those air-prune pots though as I could see how it would be a big advantage to have a larger network of feeder roots.

Yes, Alternative Crops for Drylands is my book. I'm curious that you live in TN, but did work in California. Are you a landscape architect or something along those lines?

Casey Pfeifer said:

Hi Scott,

I'm in Pikeville, TN - north end of the Sequatchie Valley - eastern TN.

The tap roots get air-pruned just like any other root, however its not as if the root is forever halted at that length. With air pruning, the root tip dessicates, and this back propagates the signal back up the root for ~ 4" to increase lateral branching as a means of finding a way around the obstacle (in this case air).

Once an air-pruned tree is replanted, ALL of those dormant air-pruned tips resume growing from apical buds - and because they haven't been cut or shorn off (i.e. ball and burlap) they are much less susceptible to disease. So if the species of tree you are growing is a "tap rooted" variety (which most are when they are young, at least) the sinker roots will resume growing as they would have, only now with a much increased mass of feeder root tips above them.

If you'd like to learn more about air pruning and how it influences root branching, including growth of formerly dormant tips after the trees are planted, I'd recommend starting with this video by Dr. Carl Whitcomb: https://youtu.be/LdGzn8kbULc

If you want to go more in depth, he has an hour long video on similar topics as well: https://youtu.be/_lkDLSPWZd0?list=RDCMUCfyN7moqhBJbILGTjPVv42g&...

My design doesn't prevent lateral root movement, but the trees are very easy to tease apart after 1 year in the beds - I documented the process in this video: https://youtu.be/sza2c9UpEf0

I did experiment with carob one year in the air-pruning beds - I didn't have great success with germination, and they grew very slowly, so don't have much direct experience to offer there.

Are you the same Scott O'Bar that wrote Alternative Crops For Drylands? If so, THANK YOU. That book is awesome and I've used it so many times as a great resource over the years for some of the designs we did in CA.

[Scott O'Bar]

Thanks for the kind words about my book.

It's kind of ironic as I'm also a resident of Tennessee now.

I had so many epiphanies watching those videos that you linked to. I wish someone would've taught me that 15 years ago. Would've saved me a lot of hassle and wasted money over the years. Judging from the myriad of plant nurseries out there still using traditional pots, I would say there is definitely a huge lack of awareness. I'm not sure why it still isn't common knowledge. Have you ever tried any of those pots that Dr Whitcomb patented? He seems to suggest that the root system is even better than what you would get with a direct-sown plant. I wonder if anyone's done a side-by-side experiment. It seems that the plant would still want to make adjustments to its root system when transplanted. After all, the air-potted root system is an adaptation to life in the pot and not life in the natural soil environment. In my experience those air-potted root balls look similar to the root systems of plants that grow in very sandy soils. I wonder if there's some degree of "over investment" in the multitude of roots, and the plant would sacrifice some of those after being transplanted depending on the structure of the soil in situ. My guess is that the root structure would spend some time rearranging itself.

In South America nurseries are even worse, because they just use those plastic bags instead of pots. I'll certainly hesitate before ever buying something from a nursery again. We were thinking about buying a grafted lime tree. Knowing what I now know, I would say it's best to get a very small specimen, and probably cut off the bottom quarter of the root ball prior to transplanting. I've seen that done here, but I worry about causing an infection.

[Scott O'Bar]

Have you heard of the work of Ernst Gotsch? I was amazed to learn about his work in tropical Brazil where he started with a heavily degraded landscape with pH of 3.7- 4.5. and he reforested the entire area. The property and surrounding landscapes had been so badly desertified that people were no longer able to grow any commercial crops. I read a translated transcript of one of his speeches where he said that he did the whole property just by direct planting seeds.

[Casey Pfeifer]

Hi Scott,

That's amazing - where have you landed in TN and what brought you here, if you don't mind sharing?

I have used several of the different pot varieties he recommends as well as some other air pot designs.

We grew a lot of cork oaks back in 2016 using Pioneer Pots of the 8ct. tray variety - https://www.blackmoreco.com/pioneer-pots - they worked pretty well for that purposed once we figured out how to keep them well hydrated in the SoCal summer heat.

I used some of the wrap-around Air Pots as well to grow a couple dozen Bunya pines back then too - wish I'd taken photos, but they worked well from what I could tell. I haven't personally had a chance to do a side by side test and follow up for several years - the best version of that I've seen came from David Muffly, who did the whole Apple building campus in Santa Clara - all of the oaks that he grew out for that project were in air pots - mostly the Pioneer Pots (though they might be out of business now? not sure...).

I'm currently using Dr. Whitcomb's 3.25" RootMakers for starting and training ~ 100 thornless honey locusts this year - I got a late start since we only arrived here in mid-May, so the trees are just about 6" tall, but I'm hoping to either up-pot them soon here, or plant them out into either another air pruning bed or in-ground bed to overwinter. I've had these pots since 2017 and they're still going strong - well built and no photo-degradation. They are expensive though, especially in comparison to a DIY air pruning bed. They're more work to keep properly hydrated due to their small size, while a larger bed has some"hydric inertia" and can ride a bit longer and maintain moisture and temperatures better. All of this can be improved once I get better infrastructure in place here - just in scramble mode this year starting from scratch.

Scott O'Bar said:

Thanks for the kind words about my book.

It's kind of ironic as I'm also a resident of Tennessee now.

I had so many epiphanies watching those videos that you linked to. I wish someone would've taught me that 15 years ago. Would've saved me a lot of hassle and wasted money over the years. Judging from the myriad of plant nurseries out there still using traditional pots, I would say there is definitely a huge lack of awareness. I'm not sure why it still isn't common knowledge. Have you ever tried any of those pots that Dr Whitcomb patented? He seems to suggest that the root system is even better than what you would get with a direct-sown plant. I wonder if anyone's done a side-by-side experiment. It seems that the plant would still want to make adjustments to its root system when transplanted. After all, the air-potted root system is an adaptation to life in the pot and not life in the natural soil environment. In my experience those air-potted root balls look similar to the root systems of plants that grow in very sandy soils. I wonder if there's some degree of "over investment" in the multitude of roots, and the plant would sacrifice some of those after being transplanted depending on the structure of the soil in situ. My guess is that the root structure would spend some time rearranging itself.

In South America nurseries are even worse, because they just use those plastic bags instead of pots. I'll certainly hesitate before ever buying something from a nursery again. We were thinking about buying a grafted lime tree. Knowing what I now know, I would say it's best to get a very small specimen, and probably cut off the bottom quarter of the root ball prior to transplanting. I've seen that done here, but I worry about causing an infection.

[Casey Pfeifer]

I haven't heard of him, no - but that sounds like an amazing story, and if you have that transcript or any other resources I would love to read about his example.

Ultimately, I'd love to do it that way too - just put seeds in the ground where I know they're going to be for the long term. Heck, that's what we're trying to do with ourselves too :)

Scott O'Bar said:

Have you heard of the work of Ernst Gotsch? I was amazed to learn about his work in tropical Brazil where he started with a heavily degraded landscape with pH of 3.7- 4.5. and he reforested the entire area. The property and surrounding landscapes had been so badly desertified that people were no longer able to grow any commercial crops. I read a translated transcript of one of his speeches where he said that he did the whole property just by direct planting seeds.

[Scott O'Bar]

https://www.youtube.com/watch?v=9zhTsYgfuyQ

That's the video I was talking about. I preferred just reading the transcript.

How much land are you planting in Tennessee? You don't want to transplant to the field in late autumn?

I have family in a suburb of Nashville, so it's mostly just a place for me to be when I'm stateside. Currently been living in Peru for the past three years.

So which pots do you recommend the most? I'm thinking about trying to start Brazil Nuts and Dipteryx alata seeds with some sort of air pot. I like that 18-pack of the Dr. Whitcomb ones you linked to. They look like they don't have enough air holes compared to most of those other pots you linked to. I'd just want something to grow the seeds for 3-5 months in the nursery until they're about 50cm and then plant them out in the field. The goal would be to get them tall enough to give them a head start competing with the grass and other weeds. I could pretty much guarantee that those pots would not be available in Peru. The market is very under served here to say the least.

[L kas]

My go-to person for air pruner beds is Sean of edibleAcres on youtube https://youtu.be/Q-htiLvbEd8 His series takes you through errors and a few design trials. The mesh fabric wouldn't last a day with the squirrels in the north east with any kind of a nut crop. We need the same hardware cloth in a frame above until seedling growth allows us to snap off the nuts - or they will clip down the seedling when removing the spent nut 🙄 Even in large beds, I have not found a need for an extra cloth to retain soil. I compact it as I am loading it in and it stays put well enough even with the torrential rains we've had this summer. I do put a half inch or so of wood shavings from a wood worker on top.
From the photo, your pruners look too shallow to establish a decent taproot. Maybe you're planting only non-tap root species or only grow for a couple of months before transitioning?
Thanks so much for a description of your willow beds. This looks like a great nursery setup - affordable and with water tied in.

[Scott O'Bar]

These are the only options for air-pruning pots I've found in Peru:

https://perugrow.com/tienda/macetas-smart-pot/

https://agriplant.com.pe/product/maceta-ercole/

https://agriplant.com.pe/product/maceta-rete/

Of which, I think probably the Smart Pots would be the only ones to fit the bill. What do you think? Do those look like they would accomplish what Dr. Whitcomb discusses? The price is about $5.50 each for the 2 gallon ones, which seems a bit pricey, but not surpised.

Casey Pfeifer said:

I haven't heard of him, no - but that sounds like an amazing story, and if you have that transcript or any other resources I would love to read about his example.

Ultimately, I'd love to do it that way too - just put seeds in the ground where I know they're going to be for the long term. Heck, that's what we're trying to do with ourselves too :)

Scott O'Bar said:

Have you heard of the work of Ernst Gotsch? I was amazed to learn about his work in tropical Brazil where he started with a heavily degraded landscape with pH of 3.7- 4.5. and he reforested the entire area. The property and surrounding landscapes had been so badly desertified that people were no longer able to grow any commercial crops. I read a translated transcript of one of his speeches where he said that he did the whole property just by direct planting seeds.