Trees in Containers - a Discussion

Bay City, MI(Zone 6a)

I have been tending and studying about tending trees in containers for close to 20 years. Most of what I've learned about plants and plant-related science has come about as an outgrowth of my pursuit of at least some degree of proficiency at bonsai. Before the plants I grow become bonsai, they are often collected from the wild or grown in the ground for a period before transitioning them to containers and then finally to bonsai pots. Often too, I simply grow them for a few years in containers before deciding to work on them or give them away.

I grow and manage a wide variety of temperate trees and shrubs, both deciduous and conifers, and 75 or more tropical/subtropical woody plants. I'd like to invite you to a discussion about your containerized trees and/or your tree problems. I will try to answer your questions whenever I can.

Al

For in the true nature of things, if we rightly consider, every green tree is far more glorious than if it were made of gold and silver. ~Martin Luther

The following information was added on 10/2/11

It's not much of a secret to many, that a good part of what I've learned about plants and plant-related science has come as an outgrowth of my pursuit of at least some degree of proficiency at bonsai. Please, make no mistake, the principles applied to containerized trees under bonsai culture can, and in most cases SHOULD be applied to all containerized trees grown for the long term. Because of the small volumes of soil and small containers these trees are grown in, you might look at bonsai as a form of container culture taken to another level. Before most of the plants I grow become bonsai, they often undergo many years of preparation and manipulation while still in the same size containers you are growing in, so while I am intimately familiar with growing plants in bonsai culture, it would have been impossible for me to arrive at that familiarity w/o an even more thorough understanding of growing woody plants in larger, pre-bonsai size containers like you grow in. This thread is a continuation of one I previously posted on the same topic.

I grow and manage a wide variety of temperate trees and shrubs, both deciduous and conifers, and 75 or more tropical/subtropical woody plants. I'd like to invite you to join the discussion with questions about your own containerized trees and/or your tree problems. I will try to answer your questions whenever I can.

The timing of certain procedures is closely related to energy management, which gets too little consideration by most growers tending trees in containers. Because repotting and root pruning seem to be most misunderstood on the list of what it takes to maintain trees that will continually grow at close to their genetic potential, I will include some observations about those procedures to open the discussion.

I have spent literally thousands of hours digging around in root-balls of trees (let's allow that trees means any woody plant material with tree-like roots) - tropical/subtropical trees, temperate trees collected from the wild and temperate nursery stock. The wild collected trees are a challenge, usually for their lack of roots close to the trunk, and have stories of their own. The nursery stock is probably the closest examples to what most of your trees are like below the soil line, so I'll offer my thoughts for you to consider or discard as you find fitting.

I've purchased many trees from nurseries that have been containerized for long periods. Our bonsai club, just this summer, invited a visiting artist to conduct a workshop on mugo pines. The nursery (a huge operation) where we have our meetings happened to have purchased several thousand of the mugos somewhere around 10 - 12 years ago and they had been potted-up into continually larger containers ever since. Why relate these uninteresting snippets? In the cases of material that has been progressively potted-up only, large perennial roots occupied nearly the entire volume of the container, plant vitality was in severe decline, and soil in the original root-ball had become so hard that in some cases a chisel was required to remove it.

In plants that are potted-up, rootage becomes entangled. As root diameters increase, portions of roots constrict flow of water and nutrients through other roots, much the same as in the case of girdling or encircling roots on trees grown in-ground. The ratio of fine, feeder roots to more lignified and perennial roots becomes skewed to favor the larger, and practically speaking, useless roots.

Initial symptoms of poor root conditions are progressive diminishing of branch extension and reduced vitality. As rootage becomes continually compressed and restricted, branch extension stops and individual branches might die as water/nutrient translocation is further compromised. Foliage quality may not (important to understand) indicate the tree is struggling until the condition is severe, but if you observe your trees carefully, you will find them increasingly unable to cope with stressful conditions - too much/little water, heat, sun, etc. Trees that are operating under conditions of stress that has progressed to strain, will usually be diagnosed in the end as suffering from attack by insects or other bio-agents while the underlying cause goes unnoticed.

I want to mention that I draw distinct delineation between simply potting up and repotting. Potting up temporarily offers room for fine rootage to grow and do the necessary work of water/nutrient uptake, but these new roots soon lignify, while rootage in the old root mass continues to grow and become increasingly restrictive. The larger and larger containers required for potting-up & the difficulty in handling them also makes us increasingly reluctant to undertake even potting-up, let alone undertake the task of repotting/root-pruning which grows increasingly difficult with each up-potting.

So we are clear on terminology, potting up simply involves moving the plant with its root mass and soil intact, or nearly so, to a larger container and filling in around the root/soil mass with additional soil. Repotting, on the other hand, includes the removal of all or part of the soil and the pruning of roots, with an eye to removing the largest roots, as well as those that would be considered defective. Examples are roots that are dead, those growing back toward the center of the root mass, encircling, girdling or j-hooked roots, and otherwise damaged roots.

I often explain the effects of repotting vs potting up like this:

Let's rate growth/vitality potential on a scale of 1-10, with 10 being the best. We're going to say that trees in containers can only achieve a growth/vitality rating of 9, due to the somewhat limiting effects of container culture. Lets also imagine that for every year a tree goes w/o repotting or potting up, its measure of growth/vitality slips by 1 number, That is to say you pot a tree and the first year it grows at a level of 9, the next year, an 8, the next year a 7. Lets also imagine we're going to go 3 years between repotting or potting up.

Here's what happens to the tree you repot/root prune:
year 1: 9
year 2: 8
year 3: 7
repot
year 1: 9
year 2: 8
year 3: 7
repot
year 1: 9
year 2: 8
year 3: 7
You can see that a full repotting and root pruning returns the plant to its full potential within the limits of other cultural influences for as long as you care to repot/root prune.

Looking now at how woody plants respond to only potting up:
year 1: 9
year 2: 8
year 3: 7
pot up
year 1: 8
year 2: 7
year 3: 6
pot up
year 1: 7
year 2: 6
year 3: 5
pot up
year 1: 6
year 2: 5
year 3: 4
pot up
year 1: 5
year 2: 4
year 3: 3
pot up
year 1: 4
year 2: 3
year 3: 2
pot up
year 1: 3
year 2: 2
year 3: 1

This is a fairly accurate illustration of the influence tight roots have on a woody plant's growth/vitality. You might think of it for a moment in the context of the longevity of bonsai trees vs the life expectancy of most trees grown as houseplants, the difference between 4 years and 400 years, lying primarily in how the roots are treated.

I haven't yet mentioned that the dissimilar characteristics of the old soil as compared to the new soil when potting-up are also a recipe for trouble. With a compacted soil in the old roots and a fresh batch of soil surrounding the roots of a freshly potted-up tree, it is nearly impossible to establish a watering regimen that doesn't keep the differing soils either too wet or too dry, both conditions occurring concurrently being the rule rather than the exception.

Most who read this would have great difficulty showing me a containerized tree that's more than 10 years old and as vigorous as it could be, unless it has been root-pruned at repotting time; yet I can show you hundreds of trees 20 years to 200 years old and older that are in perfect health. All have been root-pruned and given a fresh footing in in new soil at regular and frequent intervals.

Deciduous trees are some of the most forgiving of trees when it comes to root pruning. The process is quite simple and the long term benefits include best opportunities for plants to grow at or near their potential genetic vigor, and stronger plants that are able to resist the day to day perils that bring down weaker plants. Root-pruning is a procedure that might be considered borrowed from bonsai culture, but as noted above, bonsai culture is nothing more than highly refined container culture, and to restrict the practice of root-pruning to bonsai only, is an injustice to those of us who simply enjoy growing trees in containers.

Trees are much like human beings and enjoy each other's company. Only a few love to be alone. ~Jens Jensen

Now that I have made the case for why it is important to regularly perform full repots (not to be confused with potting-up) and prune the roots of your containerized trees regularly, I will offer some direction. Root-pruning is the systematic removal of the largest roots in the container with emphasis on removal of rootage growing directly under the trunk and at the perimeter of the root mass.

Root pruning can start immediately with year-old seedlings by removing the taproot just below the basal flare of dormant material, repotting, and treating the plant as a cutting. This will produce a plant with flat rootage that radiates outward from the base and that will be easy to care for in the future.

Young trees (under 10 yrs old) are nearly all dynamic mass and will tolerate root-pruning well. Most deciduous trees are extremely tolerant of root work. Acer buergerianum (trident maple) is routinely reduced to a main trunk with roots pruned all the way back to the basal flare and responds to the treatment with a fresh growth of fine, fibrous roots and a fresh flush of foliage each spring. The point here is, you don't need to be concerned about the pruning if you follow a few simple guidelines.

First, some generalities: undertake repotting of most deciduous material while the plant is quiescent (this is the period after the tree has met its chill requirement and has been released from dormancy, but has not begun to grow yet because of low soil temps). Most conifers are best repotted soon after the onset of spring growth. Most tropical and subtropical trees are best repotted in the month prior to their most robust growth period (summer). Citrus are probably best repotted in spring, but they can also be repotted successfully immediately after a push of top growth.

For most plants that have not been root-pruned before: With a pruning saw, saw off the bottom 1/3 of the root ball. With a hand-rake (like you use for scratching in the garden soil) and/or a wooden chopstick and/or the aid of water under high pressure from a garden hose, remove all the loose soil. Using a jet of water from the hose and the chopstick, remove the remaining soil - ALL of it. The exception here would be those plants that form dense mats of fine roots (citrus, bougainvillea, rhododendron ...). This should be done out of sun and wind to prevent the fine roots from drying. 5 minutes in the sun or wind can kill fine roots & set the tree back a week or more, so keep roots moist by misting very frequently or dipping the roots in a tub of water as you work. After the soil is removed, remove up to another 1/3 of the remaining mass of roots with a sharp pruning tool, taking the largest roots, and those roots growing directly under the trunk. Stop your pruning cuts just beyond where a smaller root branches toward the outside of the root you are pruning. Be sure to remove any J-hooked roots, encircling/girdling roots or others exhibiting abnormal growth.

Before you begin the pruning operation, be sure you have the soil & new container ready to go (drain screens in place, etc). The tree should fit loosely inside the walls of the container. Fill the container with soil to the desired ht, mounded in the center, & place tree on the mound. Add soil to cover roots & with a chopstick/skewer, or sharpened wood dowel, work soil into all voids in the roots, eliminating the air pockets and adding soil to the bottom of the basal root-flare. Temporarily securing the tree to the container with twine or small rope, even staking, against movement from wind or being jostled will fractionalize recovery time by helping to prevent breakage of newly-formed fine rootage. Place the tree in shade & out of wind until it leafs out and re-establishes in the container.

The first time you root-prune a tree will be the most difficult & will likely take up to an hour from start to finish, unless the tree is in larger than a 5 gallon container. When you're satisfied with the work, repot into a soil that you are certain will retain its structure until the next root-pruning/repot. Tree (genetic) vigor will dictate the length of time between repots. The slow growing, less vigorous species, and older trees will likely go 5 years between repots. For these slow growing trees, it is extremely important that soils retain aeration. For these trees, a soil of 2/3 inorganic parts and 1/3 organic (I prefer pine or fir bark) is a good choice. The more vigorous plants that will only go 2 years between repots can be planted in a soil with a higher organic component if you wish, but would still benefit from the 2/3 inorganic mix.

Most trees treated this way will fully recover within about 4 weeks after the repot By the end of 8 weeks, they will normally have caught & passed, in both development and in vitality, a similar root-bound plant that was only potted up

When root-pruning a quiescent plant, you needn't worry much about "balancing" top growth with rootage removed. The plant will tend to only "activate" the buds it can supply with water. It is, however, the optimum time to undertake any pruning you may wish to attend to.

This is how I treat most of my trees. Though I have many growing in bonsai pots, more of my plants are in nursery containers or terra-cotta and look very much like your trees, as they await the beginning of intensive training. With a little effort at developing a soil from what's available to you and some knowledge and application of root-pruning and repotting techniques, I'm absolutely sure that a good % of those nurturing trees in containers could look forward to results they can be very pleased with. This is the repotting technique described that allows bonsai trees to live for hundreds of years & be passed from generation to generation while other containerized trees that have not had their roots tended to, and have only been potted-up, are likely to be in severe decline, or compost, well before they're old enough to vote. ;o)

I hope you're bold enough to make it a part of your containerized tree maintenance, and I hope what I've written so far makes sense. Thank you so much for your interest.

Al

Knowing grass, I understand the meaning of persistence.
Knowing trees, I understand the meaning of perseverance.
Knowing bonsai I understand the meaning of patience.
~ Al



This message was edited Oct 2, 2011 10:22 PM

Thumbnail by tapla
Phoenix, AZ

Hello Al,
I'm interested in this impending discussion. I've recently transplanted 3 volunteer Mimosa starts from my yard. (a Mimosa tree was in the garden for years and removed by after about 10 years). Volunteers began to pop up after my two years living in the house. My starts, now in 5 gal plastic pots, are about two foot tall each, healthy it appears. I'm mostly interested in how to discover, treat, manipulate how roots grow. In my particular case do Mimosa roots grow OUT, Down or both? ... and, if they're grown in containers, large containers, can they thrive? I know I'm going to put at least one in the ground (once I decide on location). Other two may give away, but still curious as to how to maintain them in large containers.

Carry on. I'm all ears.
Susie
P.S.- I'm an absolute novice at the trees in containers concept. No knowledge to share.

This message was edited Nov 10, 2009 8:58 PM

Bay City, MI(Zone 6a)

Roots of all plants grow wherever there is ample air, water, and nutrients. Roots don't 'seek' these things out or grow toward moisture, as is commonly believed, they just don't grow where conditions aren't favorable. Even plants that are noted for their shallow root systems will fully colonize even the deepest containers with roots if the soil is well-aerated.

I don't know what you're using for soil, but with a small tree in a 5 gallon container, you need to be wary of over-watering, unless the soil is very fast (draining). Often, the top of the soil feels dry, so you water, but 6" down the soil is still very wet. This robs the tree of its ability to colonize all the soil and can impair root function and metabolism, as well as set the plant up for a variety of fungal issues (root rot). You might wish to check the dampness of the soil at the drain hole and only water when it feels dry, or insert a dowel rod deep into the soil and only water when it comes out dry. Inserting a wick through the drain hole is also a good way to drain excess water from the lower part of the soil (ask, if you don't understand this concept). The wick also serves well as a 'tell'. Just feel the wick where it exits the container - if it feels dry it's time to water.

Yes, your trees can absolutely thrive in large (or small) containers, but there are some things that can make it much easier for you to maintain them at high vitality levels. That starts with the soil. You really need a well-aerated soil that will retain its structure for long term plantings. A soil like I described guarantees your trees at least the opportunity to grow at near their genetic potential, while a poor soil guarantees it never can.

What are you fertilizing with?

I know you said you were a beginner at trees in containers, so if you need me to clarify something, just ask. ;o)

Al



Phoenix, AZ

HI Al,
I've read some of your wise advice in other threads including the soil type used in pots. In this case I used regular old Miracle Gro potting soil with the intention that this container be a short lived home for the little trees. I don't intend to keep them in "this" soil. I plan to keep only one of three in a container... and will re read your advice on soil make-up for that tree. The other two will go in the ground probably Jan. or Feb. Gets VERY cold here in DEC. - JAN and I want to be able to move them accordingly. I understand what you're saying about too much water. I can see the yellowing leaves of one that is probably in the line of fire of the sprinklers. I use only Fish Emulsion in my entire yard except rose fert. on the roses. I planted some senna fistula seeds ( or is it senna cassia?? - not cassia fistual, I know) Anyway, I put them in the ground with tree and shrub soil (from a bag purchased at the nursery). They are doing VERY well (about 5 feet in a year, and soon to flower). What do you think about repotting my Mimosa with the Tree and Shrub bagged soil (in a container)? Would it be too rich and burn? I don't want to take up too much of your time, Al, and don't worry about repeating points you've already made. I can go to back -posts you've made. THANKS! ~Susie

Bay City, MI(Zone 6a)

W/o knowing anything about the soil, I can't offer an opinion. I'm a strong proponent of durable soils for long term plantings, which means that I tend to use soils with high mineral content. Those soils I use that DO have a high organic component are based on pine bark, which outlasts peat on a size for size basis by about 3 or 4:1. When you add in the larger particle size for the bark, and the accompanying reduction in surface area because the bark is larger, you increase the bark's durability over peat even more.

With a good amount of certainty, you can say that soils that are more highly aerated and durable than peat-based soils offer much greater potential for plants to grow as close to peak vitality as allowed by remaining cultural factors. You might be able to gauge your choice of soils against that, but I don't know how I could help more.

We usually consider 'burn' to come from a high level of solubles in the soil solution. Sugar will 'burn' a plant as quickly as salt, or fertilizer salts. It's doubtful that soil from a bag could burn, unless it was fortified with fertilizers before packaging. I would say though, that you should note what the material in the bag is derived from. Composted 'forest products' can be just about anything, and often contain lots of partially composted heart/sapwood and hardwood bark. These materials are quite unsuitable as a major pert of container soils & should probably be restricted to use as mulch. I'm not sure if this applies to what you're using or not - just a cautionary offering.

Al

Barnesville, GA(Zone 7b)

Al, over time I've read many of your knowledgeable postings about soil in containers. I have a small azalea bought for my mom (who has since passed). It would be nice to turn it into a bonsai and I'd appreciate any advice on what soil to use for this. The pot it came in seems to consist mostly of peat. I'm sure it will be necessary to remove this soil before repotting. Thanks,

Bay City, MI(Zone 6a)

Your main pruning should be done in late summer in late summer. DO seal the pruning wounds (with a sealing compound that matches bark color for best appearance) or you'll get considerable necrosis of cambial tissues surrounding the cuts and ugly wounds slow to heal. (If others should wonder at this advice that seems to be contrary to contemporary thinking, remember that 'bonsai' is the key word hear and long tradition has shown sealing azalea wounds is a preferred practice). Azaleas bud back readily from old wood. New shoots grow in groups of five and should be reduced to only two from each group and the remaining shoots reduced to two sets of leaves. Be careful when bending the brittle branches, and wire in the warmer months Dry trees are more flexible, so don't try to wire recently watered trees. Bark is fragile, so wire carefully or protect with raffia when you wire.


Repot in the spring after blooms fade. Azaleas have extremely dense, matted roots, from which fine particles are difficult to remove, so use coarse soils. When using fine soils, roots form tangled mats that shed water, which makes it hard to water/fertilize. There is no need to include any peat in the soil. When repotting, trim the roots to a flat disc and cut out pie-shaped wedges, removing about 1/2 of the remaining roots. New roots will grow into the areas you removed.

Using an acid-forming fertilizer in the 3:1:2 ratio works well (MG 24-8-16 e.g.). If your (irrigation) water is alkaline, it helps to neutralize alkalinity to water pH is around 5.5. You can use pH strips to test - just measure out enough white vinegar to bring the pH down to 5.5 and add that amount to your water each time you water.

That's about all I can think of for the basics.

Ohh! Important: This plant is NOT apically dominant. Most trees/shrubs concentrate energy at the top of the tree/plant, but azaleas grow strong at the bottom, so you should be pruning the lower part of the plant much more aggressively than the top.

Al


Barnesville, GA(Zone 7b)

thanks for the info Al and one more question. I know when planting in the ground, azaleas need to be planted slightly above the soil level....would this hold true when trying to bonsai it?

Bay City, MI(Zone 6a)

Yes. The exposure to light and air thickens the root base (nebari), but in the coarse soils you should be using, there is no physiological advantage in it.

Al

Santa Cruz, CA(Zone 9b)

Hello Al,
Thanks for making yourself available. I have three potted J maples two are crimson queen and the other in unknown but resembles bloodgood. I got them as maidens or very newly grafted. They are all 2-3 years old. I'm thinking I should repot them every year to put them in soil that is less decomposed to maintain good drainage. Should I do anything to the roots? I'm thinking I will try to plant the "bloodgood" at the house we just bought but I don't know where I'm going to put it just yet. the others I am contemplating keeping in their pots for a while but maybe planting them eventually. I'm not sure how to get one out if its pot because it is a little narrowed at the top Its a beautiful pot and I'd rather not break it. Any suggestions? Right now I'm using gardener and bloom potting soil and they do not have wicks. Am I right in thinking that a wick is just a piece of towel twisted up and placed along the side of the pot and then through the drain hole a few inches? I would like to put one in when I repot, but not totally sure about the proper procedure. I read your post about soil for pots and have been using a "planting" mix now that is composed of bigger particles of bark/wood and other things for improved drainage, but as it is still mostly wood chips it is probably degraded. They are in a five gal, seven and ten sized pots. I believe they are suffering from poor drainage as the tips of the leaved were brown all season and they seemed to drop their leaves a little early. Also, I live by the sea and many J maples get fussy here so its hard to tell what's really going on.

Sacramento, CA(Zone 9a)

Wonderearth - I'll let Al respond to your post in greater detail, but for what it is worth, the brown or burnt tips of the leaves are pretty common for Japanese maples especially when they get a lot of afternoon sunlight or hot winds. Then again, if you have poor drainage, the JMs would protest against their wet feet too.

Bay City, MI(Zone 6a)

If you intend to keep your trees in containers, you should plan on yearly root pruning or an alternate plan of potting up one year and then root-pruning the next. Usually, you can use the same size container after root pruning, or in some cases, return to the container the tree was in when you last potted up. Root pruning and/or potting up is very important to o/a vitality. Plants that become extremely root bound because the plants weren't bumped up or root pruned are often permanently disadvantaged (even when planted out) unless you get into the roots at some future date and correct the problems. Even then, they can never really recover the development they would have had if roots had been tended to properly to begin with. BTW - the entire Acer genus generally tolerates root work well.

Usually, you can get the plant out of pots that narrow at the rim w/o much serious damage if they're not seriously root bound. Consider too, that if you intend to prune the roots it's likely any damaged roots at the perimeter will be removed anyway.

The soil is very important. Soils with a large presence of pine bark are preferred to those based on peat, coir, or compost; and gritty soils of 2/3 or more mineral content (large particles, like Turface, calcined DE, and crushed granite) offer the potential of being even more productive and closer to fool-proof than the bark-based soils. Please try to use conifer bark in your soils. Hardwood bark and any sapwood/heartwood, as well as 'composted forest products', each present their problems and are better left out of container media.

I use strands from a rayon mop for my wick material. The mop heads can be had at most Ace Hardwares and Wallyworld. Make sure they are rayon, though. You can also use shoelaces or other material that readily absorbs water as a wick, though cotton isn't a good choice because it decomposes too rapidly.

JMs exhibit leaf scorch for a variety of reasons, and poor drainage is surely one of them. Too much sun/wind, insufficient water, too much water, a high level of soluble salts in the soil, high soil temperatures, and combinations of these cultural conditions that aren't necessarily extreme are some other common causes.

I didn't go into much depth, so if there is something you would like me to expand on, let me know.

Al





Santa Cruz, CA(Zone 9b)

Thanks so much. How do I find out how to root prune? I was reading about root pruning it a bonsai book but Im not quite confident. And, Should I repot while dormandt or while actively growing?

Bay City, MI(Zone 6a)

If the tree will be subjected to freezing temps, it's better to root-prune in spring immediately before budswell, but in your zone, you can prune roots almost anytime after the tree goes dormant, but before budswell.

This is a copy/paste job of something I wrote on another forum site. It was on a forum about maples, so the info should be appropriate. If it seems a little off topic, please remember it was copy/pasted as it was written for another thread:

In other threads, I have made my best case for why it is important to prune roots and do a full repot (not to be confused with potting-up) on your containerized Acers - regularly. Root-pruning is the systematic removal of the largest roots in the container with emphasis on removal of rootage growing directly under the trunk and at the perimeter of the root mass.
Root pruning should start immediately with year-old seedlings by removing the taproot just below the basal flare of dormant material, repotting, and treating the plant as a cutting. This will produce a plant with flat rootage that radiates outward from the base and will be easy to care for in the future.

Young trees (under 10 yrs old) are nearly all dynamic mass and will tolerate root-pruning well. The entire genus of Acer is extremely tolerant of root work. Acer buergerianum (trident maple) is routinely reduced to a main trunk with roots pruned all the way back to the basal flare and responds to the treatment with a fresh growth of fine, fibrous roots and a fresh flush of foliage each spring. The point here is, you don't need to be concerned about the pruning if you follow a few simple guidelines.

First, undertake the root-pruning and repot while the plant is quiescent (this is the period after the tree has met its chill requirement and has been released from dormancy, but has not begun to grow yet because of low soil temps). The ideal time is immediately before buds move (swell) in spring. Next best time is at the onset of budswell. Next best time is anytime late in the quiescent period.

For plants that have not been root-pruned before: With a pruning saw, saw off the bottom 1/3 to 1/2 of the root ball. With a hand-rake (like you use for scratching in the garden soil) or a wooden chopstick, remove all the loose soil. Using a jet of water from the hose and the chopstick, remove the remaining soil - ALL of it. This should be done out of sun and wind to prevent the fine roots from drying. 5 minutes in the sun or wind can kill fine roots & set the tree back a week or more, so keep roots moist as you work. After the soil is removed, remove about 1/2 of the remaining mass of roots with a sharp pruning tool, taking the largest and those growing under the trunk. Stop your pruning cuts just beyond where a smaller root branches off the root you are pruning. Be sure to remove any J-roots, encircling roots, or others with abnormal growth.

The first time you root-prune a tree will be the most difficult & will likely take an hour from start to finish, unless the tree is in larger than a 5 gallon container. When you're satisfied with the work, repot into a soil that you are certain will retain its structure until the next root-pruning/repot. Tree (genetic) vigor will dictate the length of time between repots. The slow growing, less vigorous species will likely go 5 years between repots. For these slow growing trees, it is extremely important that soils retain aeration. For these trees, a soil of 2/3 inorganic parts and 1/3 organic (I prefer pine or fir bark) is a good choice. The more vigorous plants that will only go 2 years between repots can be planted in a soil with a higher organic component if you wish, but would still benefit from the 2/3 inorganic mix.

Before you begin the pruning operation, be sure you have the soil & new container ready to go (drain screens in place, etc). The tree should fit loosely inside the walls of the container. Fill the container with soil to the desired ht, mounded in the center, & place tree on the mound. Add soil to cover roots & with the chopstick, work soil into all voids in the roots, eliminating the air pockets and adding soil to the bottom of the basal root-flare. Temporarily securing the tree to the container with twine or small rope, even staking, against movement from wind or being jostled will speed recovery time by preventing breakage of newly forming fine rootage. Place the tree in shade & out of wind until it leafs out and re-establishes in the container.

Most trees treated this way will fully recover within about 4 weeks. By the end of 8 weeks, they will have caught & passed a similar plant, that was allowed to remain in its container, in both development and in vitality.

When root-pruning a dormant plant, you needn't worry about "balancing" top growth with rootage removed. The plant will only "activate" the buds it can supply with water. It is, however, the optimum time to undertake any pruning you may wish to attend to.

This is how I treat all my deciduous material. Yes, I have quite a few growing in bonsai pots, but more of my plants are in nursery containers or terra-cotta and look very much like your trees as they await the beginning of training. With a little effort at developing a soil from what's available to you and some knowledge and application of root-pruning and repotting techniques, I'm absolutely sure that a good % of those growing trees in containers could look forward to results they can be pleased with. This is the repotting technique that allows bonsai trees to live for hundreds of years & be passed from generation to generation while other containerized trees that have not had their roots tended to, only potted-up, are likely to be in severe decline or compost before they're old enough to vote.

Questions?

Al


Barnesville, GA(Zone 7b)

Al, you have certainly answered most any questions one would have and thank you for the advice. Now, have you ever made a video showing this? If not, a book you could recommend? The root pruning, while you have explained in fine detail, just scares me and seeing it done step-by-step would be so much better. Sounds like I need to visit a bonsai master..........LOL.

Santa Cruz, CA(Zone 9b)

Yes I feel the same. I was like 1/3 to 1/2! Oh my! Frightening! I guess just do it is the attitude you got to adopt.

Bay City, MI(Zone 6a)

I probably can piece together some pictures when I get home. ;o)

Al

Santa Cruz, CA(Zone 9b)

Hehe that would be more than generous.

Bay City, MI(Zone 6a)

There's a story that goes with these pictures.

Once upon a time, a guy from church gave me a plant that he didn't know what to do with. It wasn't too healthy, and had grown way out of reasonable bounds. My intent was to rehab the plant & give it to someone else at church. It looked like this when I got it:

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Bay City, MI(Zone 6a)

So I gathered the tools I knew I'd be using

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Bay City, MI(Zone 6a)

And set about the initial top reduction

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Bay City, MI(Zone 6a)

I decided that wasn't enough off the top, so I went a little further

This message was edited Nov 25, 2009 1:34 PM

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Bay City, MI(Zone 6a)

before I unpotted the tree

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Bay City, MI(Zone 6a)

You can see that my next step was to saw off the bottom 2/3 of the root mass

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Bay City, MI(Zone 6a)

which left me with something looking like this:

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Bay City, MI(Zone 6a)

After I bare-rooted what remained of the root mass, it looked like this:

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Bay City, MI(Zone 6a)

I then repotted it into this soil

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Bay City, MI(Zone 6a)

and it ended up looking like this

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Bay City, MI(Zone 6a)

Somewhere, I have a pic of the plant as it was starting to back-bud, but I can't find it. What happened was pretty cool, though. I had been helping people with their trees on another site, and a guy that had been looking for help contacted me by email. He said that his fiance had entrusted him with her scheff while she was out of the country, and he had killed it. What he was actually hoping is that I could somehow help him resurrect it, but that wouldn't fly. What I suggested was that he check with her to see if the one I had would be an appropriate replacement, and if it was, I'd send it to him. After all, the pictures had been published on the other forum and the tree had some degree of notoriety. ;o)

Well anyway, I ended up shipping it off to New York or Boston, some place in the EAST, and a few weeks later I got a picture back of the plant just getting settled in its new home.

Here it is. Try to focus on the plant, guys.

Al

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Barnesville, GA(Zone 7b)

Very helpful......thanks again. It appears the plant loved your work and so did it's lady. Now I'll have to go back and re-read the info about the soil you use.

Santa Cruz, CA(Zone 9b)

Before root pruning you took some growth off the top. For my J maples, I was told as they are young trees, that they should be left to develop their structure without pruning for the first bit. If the roots and the top aren't pruned in balance could the tree with suddenly fewer roots not be able to sustain its existing top growth? Does this make sense? I guess what I'm asking is - Do I have to prune the top if I'm going to prune the roots?

Santa Cruz, CA(Zone 9b)

On another topic do potted brugs need this same treatment? I'm thinking of trying to grow one in a pot.

Bay City, MI(Zone 6a)

Maple: I need to temper my answer by saying that there are times when it is necessary to prune some of the canopy to balance with what volume of foliage the roots can supply with water (like when you repot or dig up a deciduous tree when it's in leaf), but the answer that fits most applications is 'NO', don't worry about 'balancing' the ratio of roots:shoots. It's generally considered a fallacy that you need to balance plants in such a way. Roots grow and plants establish based on the photosynthate created by the foliage. 'Balancing' roots:shoots by removing branches or foliage after you root-prune is like trying to build a mall in 3 months after you've just laid off the workers. ;o)

For plants that are lifted at inappropriate times, it's sometimes better to prune part of the canopy back, though. The reason is that it is likely that some of the canopy will be shed when roots cannot supply shoots. It's better if YOU select the branches that need to go (and stay), rather than allowing the tree to shed branches that might be key to your vision for the plant. We're getting into the realm of energy management here now, which can be a very important consideration - especially for containerized trees.

Brug: Any plant that becomes seriously root-bound will be permanently unable to grow at or near it's potential genetic vigor, even if all other conditions were perfect. You've all experienced the bedding plants in cell packs that came with very tight roots. Remember? You planted them & they did just about nothing all summer long, and when you dug them up in the fall you discovered that the roots were still in a shape so compact you could probably have put them right back in the cell pack it came out of.

I'm not going to tell you that your brugs are going to die, or that they won't bloom, if you don't tend to their roots, but if you use this as a rule of thumb, you'll be in pretty good shape: If you pull the plant from the pot and the root ball holds together, at a minimum you should pot-up at that time. If you want to maximize vitality, knock all or almost all the soil off brugs and root-prune every spring before they take off. They handle it very well and root-pruned plants will almost always have caught and passed their unroot-pruned counterparts in growth by summer's end. I over-winter cuttings each year that I start in the early fall, and even THEN, I root-prune in spring.

Al

Santa Cruz, CA(Zone 9b)

Whew. Awesome Thanks so much for the detail. It one thing to read and another to have the info interactive. Thanks a bunch.

Sun Lakes, AZ(Zone 9a)

Hi Al,
Another question on the brugs--what do you start them in in the fall?

Bay City, MI(Zone 6a)

I start the brugs in either of the soil mixes I use. One is

5 parts pine bark fines
1-2 parts perlite
1 part peat

the other is

1 part screened pine or fir bark
1 part screened Turface or NAPA floor-dry
1 part crushed granite (grower size grit) or #2 cherrystone

The latter is what I grow all my trees & long term plantings (like houseplants) in.

You could easily start them in 100% perlite (try to stay away from vermiculite), screened Turface or NAPA floor-dry, or chopped sphagnum moss (not to be confused with sphagnum peat), or any combination of the moss and the other ingredients. The moss is a superb medium for starting cuttings as it promotes rooting AND has anti-fungal properties.

Al

Sphagnum moss:

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Sun Lakes, AZ(Zone 9a)

Okay, thanks a lot for the advice. I am familiar with the sphagnum moss because I worked in a greenhouse in Rhode Island years ago and we used it there. I have some and the perlite so I will use that.

Pahoa, HI(Zone 10b)

so you trim the roots and limbs at the same time? I trim the roots then wait a couple of weeks and if the plant looks to be doing good then I trim the branches.

Bay City, MI(Zone 6a)

Not as an across the board practice, by any means. I usually do one operation or the other and then wait for the tree to at least partially recover before heaping additional indignities on it. It depends on the plant, and, on the level of vitality/stored energy. It usually ends up being a judgment call, but in genetically vigorous genera/species like scheffs (HF and I are having a discussion about a schefflera on another forum) it moves more toward a given that you can do both ops at once if you prefer. If you're a little concerned, do the roots first & leave the photosynthesizing machinery intact to provide photosynthate to regenerating roots. I could have been clearer, but my main intent was to make the observation that the foliage appeared to be concentrated mostly at branch ends (usually a result of being root bound or a N deficiency), making steps to bring it back in toward the center of mass for a more compact tree desirable.

Al

Pahoa, HI(Zone 10b)

oic...I did not know what N deficiency could do that too.

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