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Ficus Trees in Containers

posted by: tapla on 10.19.2010 at 10:59 pm in House Plants Forum

The previous thread about ficus culture has reached the limit of 150 posts twice. The last thread was hurriedly put together, and addressed issues as they arose. Hopefully, this will cover most of the areas where questions arise regarding how to best maintain Ficus in containers.

The information I am supplying comes from knowledge gleaned from diligent pursuit of the physiology of woody plants, and in many cases from the pursuit of information specific to various Ficus species. In order that I might be proficient at maintaining trees in containers over the very long term, I have also spent a considerable amount of time and effort gaining a command of other plant sciences, with soil science, soil/water relationships, and nutrition getting special attention. My habit is to share information, particularly information I have verified via my own practical experience and observations, my experience running to more than 20 years of maintaining healthy Ficus specimens in containers. I�m also called upon frequently to share in the surrounding communities, teaching other gardeners and bonsai practitioners how to maintain healthy containerized trees; and in general, how to get more from their container gardening experience.

From the family: Moracea (relative of mulberry)

Native: India, other tropical - subtropical regions

The Ficus genus
with more than 800 known species, is undoubtedly an extremely popular choice as a containerized tree. It tolerates the "dryer than desert" conditions actually found in many or most centrally heated homes reasonably well, and is endowed with a natural genetic vigor that makes it easy to grow. There is however, much myth and misconception regarding the care of this plant and the reasons it reacts as it does to certain cultural conditions. I would like to talk a little about the plant and then offer some specific information regarding its culture. I will primarily address Ficus benjamina - the 'weeping fig', but the commonly grown Ficus elastica - rubber tree, has the same cultural preferences. In fact, we can virtually lump all the Ficus species commonly grown as houseplants into a single group in all areas except light preferences. We need to make allowances for some of the fig species that won't tolerate direct sun as well as benjamina and elastica, and we may as well expand that exception to the variegated cultivars of benjamina and elastica as well.

Ficus benjamina
is one of the species of Ficus commonly referred to as a strangler fig. It often begins its life in duff, in the crotch of a tree, or high on a branch as a seed deposited in the droppings of a bird or other tree-dwelling animal. After the seed germinates and as it grows, it produces thin aerial roots that often dangle in the moist air or attach themselves to the host trunk, while gaining nutrients and moisture from the air, leaf litter, and the bark of the supporting tree. It does not actually parasitize the plant it grows on, it only uses it as support. This relationship is termed epiphytic, or the tree an epiphyte. Those familiar with the culture of orchids and bromeliads will recognize this term.

After the aerial roots have formed and extended, and when they finally reach the ground, the tree begins a tremendous growth spurt, sending out more roots and developing a dense canopy that eventually shades out the supporting tree at the same time the roots are competing for nutrients in the soil and compressing the trunk and branches of the support tree to the point of stopping sap flow. Eventually the supporting tree dies and all that is left where it once stood, is a hollow cavity in the dangling Ficus roots that have now thickened and self-grafted to become the trunk. It is easy to see how many of the trees in the Ficus genus have come to be called by the name 'strangler figs'.

Roots and soil
The roots of some Ficus species are so powerful they can destroy concrete buildings or buckle roads, and can be measured in miles as they extend underground in search of water. When we consider the young tree and its ability to obtain sufficient moisture from just the surrounding air and bark surface of the support tree by way of aerial roots, we can draw an important conclusion: All species of Ficus prefer well-aerated and fast draining soils. In this regard, they are actually no different than any other tree you would endeavor to grow in a container, so try always to use a soil that guarantees an ample volume of air in the soil and excellent drainage for the intended interval between repots. This can be accomplished by using a soil whose primary fraction is comprised of large particles (like pine bark) combined with ample volumes of perlite or other inorganic ingredients like Turface, pumice, Haydite, crushed granite, or others. I grow all my Ficus in a soil mix consisting of equal parts of pine or fir bark, Turface (a calcined clay product), and Gran-I-Grit (crushed and screened granite). To be fair, I will add a qualifier here: the cost of the potential for superior growth and added vitality when using these fast (draining) well-aerated soils comes in the form of you needing to be prepared to water more frequently as the soil particle size increases. Roots are the heart of the plant, and the rest of the plant can do nothing without the roots� OK - the top just THINKS it's in control. Take care of the roots, and if your other cultural conditions are favorable, your plants will thrive.

Before I go on
I would like to say there is a very important relationship between your choice of soil, your watering habits, and a very common and serious problem that too often goes completely undiagnosed. That problem is a high level of soluble salts in the soil. When we choose soils that hold water for extended periods, we put our trees at risk for the fungal infections that cause root rot. Reasoning tells us that to avoid the root rot issue, we should not water to the point of soil saturation; rather, we often feel that watering in sips to avoid the specter of root rot is the wise alternative. This strategy though, puts us squarely on the horns of a dilemma. If we don't/can't water copiously on a regular basis, the soluble salts, i.e.,all the dissolved solids in our tap water and fertilizer solution accumulate in the soil. As the level of salts in the soil increases, the plant finds it increasingly difficult to absorb water and the nutrients dissolved in water. If the salt level gets too high, it can actually 'pull' water OUT of cells in exactly the same fashion that curing salt 'pulls' moisture from ham or bacon. This 'reverse osmosis' causes plasma to be torn from the walls of cells as they collapse, killing cells and tissue. The technical term for this is plasmolysis, but we more commonly refer to it as fertilizer burn. Fertilizer burn can occur whether or not we use fertilizer. The salts in our tap water alone, can/will eventually build to the point where water uptake is impossible, unless we actively take precautions.

Watering
Ficus b. will tolerate dry soil quite well. Allowing the soil to completely dry; however, will result in undue drought stress and accompanying leaf loss, an expensive affair, considering the plant will call heavily upon energy reserves to replace lost foliage - reserves that might better have been directed to other functions and growth. If you wait just until the soil feels dry to the touch at the drain hole before watering, your tree will be free from the effects of drought stress. Soils feel dry to the touch when their moisture content is somewhere between 40-45%, but Ficus can still extract water from soils until moisture content drops to about 25-30%, giving you a 10-15% cush AFTER the soil feels dry. Use a finger or a sharpened wooden dowel stuck deep into the soil to check for moisture content. A wooden skewer or chopstick used in similar fashion is also a useful tool, and feeling the soil at the drain hole and withholding water until it feels dry there, is also a good way to judge. Water meters are rather ineffective, They actually measure EC (electrical conductivity). To illustrate: Insert a clean probe into a cup of distilled water. It will read 'DRY'. Add a little table salt of fertilizer, it will read 'WET'.

I try never to water my Ficus with cold water, opting for room water or ambient temperature water. The best way to water your Ficus it to apply water slowly until you estimate the soil is almost wet enough that water is about to appear at the drain hole. Wait a few minutes and water again so at least 10-15% of the total volume of water applied exits the drain. The first watering dissolves accumulated salts in the soil and allows them to go into solution. The second watering carries them out of the container. We already illustrated the importance of using a soil that allows us to water in such a manner without having to worry abut root rot. If you feel you cannot water in this manner without risking lengthy soil saturation and the possibility of root rot, your soil is probably inappropriate for the plant. Lest anyone complain at that observation, I would point out there is a difference between the growth and vitality of plants that are only tolerating a soil vs. the same traits in plants that appreciate (thrive in) a medium with superior properties.

More about soils as questions arise ....

Light
Although many Ficus begin life as an understory tree and are generally quite shade tolerant, most actually spend their life struggling through the shaded understory until they eventually reach the forest canopy, where they finally find full sun and can begin to come into their own. We should give Ficus all the sun they will tolerate. I grow all varieties of Ficus b. in full sun, and they tolerate it well - even some of the newer cultivars that are supposed to be extremely shade-tolerant.

I have often read anecdotal assertions that Ficus b defoliates at the slightest change in light levels (or temperature). I have found this to be only partly true. Any trees I have moved from a location with a lower light level to a brighter location have not suffered leaf loss (abscission). Instead, they have rewarded me with more robust growth and back-budding. If the change is reversed, so the tree is moved from high irradiance levels to a dimmer location, leaf loss is probable, but even then it depends on both the suddenness of the change and the difference between the two light levels. It might be interesting to note that trees that are being grown out, or allowed to grow unpruned, are most likely to suffer loss of interior leaves when light levels are reduced. Trees in bonsai culture, or properly pruned trees where thinning has occurred to allow more light to the trees interior are less affected.

Indoor supplemental lighting is a broad subject, but if you have the ability to provide it, your trees will definitely show their appreciation. Brighter light = smaller leaf size, shorter internodes, and superior ramification (finer branching), not to mention a marked increase in overall mass.

Temperature
Expect the most robust growth characteristics when the plant is kept in a temperature range between 60-80* F. Actual root temperatures above 90-95* should be avoided because they impair root function/metabolism and slow or stop growth. Temperatures below 55* should also be avoided for several reasons. They slow photosynthesis to the degree that the plant will necessarily call on stored energy reserves to power metabolism and keep its systems orderly. This essentially puts the tree on 'battery power' - running on its energy reserves. After exposure to chill and subsequent return to more favorable temperatures, the plant does not quickly recover the ability to carry on normal photosynthesis. The time needed for the plant to recover its normal photosynthesizing ability is more appropriately measured in days, than hours. Leaf loss can also occur as a result of exposure to chill, particularly sudden chill.

It is prudent to select a location free from cold breezes for your tree. Even short exposure to very cold draughts can cause leaves to abscise (fall/shed). The cool temperatures slow or halt the flow of auxin (a growth regulator - hormone) across the abscission zone at the base of each leaf petiole (stem) which allows an abscission layer to form and causes leaves to fall. Chill also stimulates an increase in abscissic acid (also a growth regulator - hormone) which is also a player in leaf loss.

Benjamina can tolerate temperatures as low as the mid-30s for brief periods if the exposure to chill is gradual, but it should be noted that even though there may not be any readily visible impact on the tree, the tree will always be in decline at temperatures below about 55* because of the impact on the tree's inability to carry on efficient photosynthesis. Sudden and large temperature drops can cause varying degrees of chill injury in the plant, caused by phenolic compounds leaking from cells, which shows up looking much like freeze damage. Severe injury could occur in plants that were growing at 80-85* and were subjected to sudden chilling to temperatures as high as 45-50*

Humidity
Benjamina's thick, leathery leaves with waxy cuticles help to limit moisture loss, making the plant suitable to a wide range of indoor humidity levels, even though it prefers humidity levels above 50%. When humidity levels are blamed for leaf loss or necrotic leaf tips and margins, it is likely the blame has been misplaced. Those pesky high salt levels in soils, most common in late winter, can make it difficult and in extreme cases impossible for the plant to absorb water to replace that being lost to the air through transpiration. The fast soils that allow copious watering, which flushes the soil of salts regularly are actually much more important/beneficial than maintaining ultra high humidity levels. Misting is very effective ..... For about 30 seconds. Forget the misting please, it is ineffective. For small plants, a humidity tray may marginally effective.

Fertilizer
I prefer any 3:1:2 ratio soluble fertilizer like Miracle-Gro 24-8-16 or 12-4-8, and I especially like Dyna-Gro's Foliage-Pro 9-3-6, because it provides all the essential nutrients in the approximate ratio the plant will use and in favorable ratios to each other. Alternately, a 1:1:1 ratio fertilizer like MG 20-20-20 is suitable. Because I use fast soils, I can fertilize at very low doses, every time I water. How YOU can/should fertilize is something we should discuss. It can change by season, and also varies based on soil choice and watering habits.

There is no question that in addition to offering greater potential for growth and vitality within the limits of other cultural factors, fast draining, well-aerated soils also get the nod for greatly increasing the grower�s margin for error in the areas of watering and fertilizing.

Defoliating
Leaf loss in Ficus is probably the cause of more conjecture than any other aspect of its culture, so even though I have mentioned it above, I will reiterate. Even though it is widely held that Ficus b. defoliates at virtually any cultural change, with changes in light and temperature most often cited, it is not so. The plant tends to defoliate when there is a fairly abrupt change in light levels - from bright to dim, or after exposure to sudden chill, but the plant does not tend to defoliate when the cultural conditions of light and temperature move from unfavorable to favorable, i.e. from dim to bright or from cool to warm/appropriate - unless the change is markedly radical.

Repotting
First, I draw a major distinction between potting-up and repotting. Potting up can be undertaken at any time. It involves moving the plant to a slightly larger pot and back-filling with fresh soil, with a minimal amount of root disturbance. Much to be preferred to potting-up, is repotting. Repotting, which has a substantial rejuvenating effect, includes removing all or almost all of the old (spent) soil and selective root-pruning. It is by far the preferred method and probably the most important step in insuring your trees always grow at as close to their potential genetic vigor as possible. Repotting as opposed to potting-up is the primary reason bonsai trees are able to live in small containers for hundreds of years while the vast majority of trees grown as houseplants are lucky to survive more than 5 years without root work

It is pretty much universally accepted among nurserymen, that you should pot up at or before the time where the condition of the roots/soil mass is such that the roots and soil can be lifted from the container intact. Much testing has been done to show that trees left to languish beyond this point will have growth and vitality permanently affected. Even when planted out, growth and longevity of trees allowed to progress beyond this point is shown to be reduced.

The ideal time to repot a Ficus, is when the plant has good vitality and in the month prior to its most robust growth. June and July are prime months for most of the US. HOW to properly repot is beyond the scope of the initial post, but I am sure the subject will be covered in detail as questions arise.

Remember - potting up a root bound plant is a stopgap fix, and ensures the plant has no opportunity to grow to its genetic potential within the limits of other cultural factors; while fully repotting, which includes a change of soil and root pruning, ensures the plant WILL have the opportunity within the limits of other cultural factors. Strong words, but to repeat the illustration: the bonsai tree is capable of living in a tiny pot, perfectly happy for hundreds of years, while we struggle to squeeze 5 years of good vitality from a root bound plant - root work being the difference.

Pests
Ficus trees suffer from some pests. Most common are scale, followed closely by mites and mealies. I have always had good luck with neem oil as a preventative and fixative. We can discuss infestations and treatment as it arises, but so it gets included in the original post, I use only pure, cold-pressed neem oil, such as that packaged by Dyna-Gro in the black and white container. The beneficial active ingredient in neem is azadirachtin, the effectiveness of which is greatly reduced by steam and alcohol extraction methods, which brings us full circle to why I use the cold-pressed product.

Oedema can sometimes be an issue as well;. Suspect it if you see corky patches on the leaves, usually preceded by wet, bumpy patches that usually go unnoticed.

This is a long post, and took a long time to compose. I hope it answers most of your questions, but somehow, I cannot help but hope there are a few lingering that you would like to ask or points you would like to have clarified. It is great fun visiting and helping people who are devoted about improving their abilities to provide for their trees.

Best luck.

Al

Here is a link that might be useful: Link to the previous thread

NOTES:

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clipped on: 09.07.2012 at 02:39 pm    last updated on: 09.07.2012 at 02:40 pm

(u)Keeping(/u) Them Looking Good .......

posted by: tapla on 11.09.2011 at 09:32 pm in House Plants Forum

About a week ago I was asked to write something about what drives a plant's reaction to pruning, and how we can use the plant's predictable response to pruning to help us keep our plants attractive and establish control over their growth habit. I'm not really sure where to start, so I'm going to muse a little about 'goals', hopefully to help establish some (of your) priorities, with the confidence that there will be a 'lead-in' to the pruning discussion as that topic winds down.

How many of us actually work toward an established goal when it comes to our plant's appearance? Probably only a few. Most of us water when we think the plant needs it, fertilize using the same method, give our plants the best light we can, and maybe pot up now & then. We want our plants to grow fast, stay nice and green, and look attractive at all times.

Growing fast doesn't necessarily equate to good health, and surprisingly .... neither does a plant's being vividly green. In both cases, we can manipulate nutrition to the plant's disadvantage in order to achieve faster growth or greener color, so when the advice to add Epsom salts or ferrous sulfate (Ironite) to plants to 'green them up' comes along, remember that the advice is usually coming from someone who really doesn't understand nutrition .... or they would be suggesting an approach with less potential to be limiting; or would understand that the odds of there being actual magnesium or iron deficiencies based on a scarcity of the elements in the soil are in most cases very remote.

The first aspect to consider when it comes to keeping our plants attractive is their health, that is, their vitality. A plant's vitality is measured in how well it is able to function within the limiting effects of its cultural surroundings. While the word "health" covers a LOT of territory, the 3 primary cultural influences that most affect the appearance of the plant are soil choice and watering habits, light, and nutrition.

Root health is key to an attractive plant. There is no chance for a healthy plant unless the root system is healthy, so find a thread that addresses how water and soils interact & gain an understanding of that relationship so you can consistently provide a healthy root environment. Learn to do full repots instead of potting up. Find a good thread about nutrition and establish a GOOD nutritional supplementation program that ensures your plants are getting all they require. Resist adding a little extra this and that - TRUST your program once you're sure it's supplying all nutrients in a favorable ratio. Light is very important, but not something we can change much. You either have good light or you don't. Many of us supplement lighting where we can. It's important to understand that lack of light can be extremely limiting. Do the best you can. Ask, if you want referrals to threads that cover soils & nutrition.

Note that all issues so far relate to health/vitality. If you maintain the considered effort to ensure your plant's good health, keeping it as your focus, the rest will take care of itself - until it comes to controlling your plant's growth habit in order to keep it looking attractive. If you think a 25 ft long vining plant that winds around itself half a dozen times before it strikes out across the mantel and back, or perhaps that Ficus that has hit the ceiling 3 feet ago, or even the Aeonium stalk bearing that single rosette on the end of a 2 ft stalk you have lashed to a stake illustrates growing prowess, there's no need to read on. ;-)

The growth habit of some plants is such that they offer little opportunity for guidance toward a more attractive appearance, but many plants DO. In fact, many plants require regular intervention if the grower has any sort of vision of how they want that plant appear, or they require intervention to return them to something you feel is appealing to the eye - rejuvenation. We all approach growing differently, but if I have a plant that doesn't look good - that doesn't have eye appeal - you can bet I have a plan in place to change that. For me, because I'm able to maintain a high level of vitality in practically everything I grow, it mostly comes down to pruning and understanding how to manipulate plants so the will of the grower instead of their growth habit prevails.

There are two hormones (growth regulators) that control how a plant grows and how it responds to pruning. Understanding the relationship between these hormones forms the basis for all intelligent pruning; that is, all pruning with a plan. First though, I want to touch on something that is an important consideration that has to do with vigor.

The most vigorous part of your plants is and remains the tissues closest to where the stem transitions to roots - the basal part of the plant. Plants do not age like people, they age ontogenetically as opposed to chronologically, like us. W/o getting complicated, this means that a plant's tissues tend to retain their ontogenetic age. The tissues nearest the base will always be youngest (ontogenetically) so they retain their juvenile vigor. That is why when you cut many plants back to the ground, they virtually explode with juvenile growth. It's no accident that this type of pruning is called rejuvenation pruning and can be applied to a significant % of house plants.

Note too, that pruning roots back closer to the junction between roots and shoots has the same rejuvenating effect on both roots AND shoots. Many think it's utterly taboo to fuss with a plant's roots, but they couldn't be more wrong. Root pruning and full repots, including removal of all soil as opposed to simply potting up, have a rejuvenating effect and are an important part of long term maintenance - a far superior approach to potting up. We can talk more about that if there is interest - especially about timing repots.

I mentioned that there are 2 growth regulators that primarily determine how a plant grows. Auxin, is produced primarily in apical meristems (the growing tip of a stem or branch), but is also produced in leaves. Its movement in plants is 'polar', which means that it moves downward toward roots. As it moves downward, it prevents buds proximal (closer to the roots) to the growing tip of the branch from becoming active.

Cytokinin is the other hormone we need to consider. It is produced in the roots, its movement is also polar - upward. It tends to stimulate growth of dormant buds. It's easiest to understand the relationship between these two hormones as an antagonistic one. Think of them as always fighting against each other for control of how the plant grows. If auxin is dominant, the plant grows long as it suppresses the buds that turn into lateral growth and make the plant bushy. If cytokinin is dominant, we get a bushier plant with more lateral branching. In most plants, auxin is the dominant growth regulator ...... but it doesn't HAVE to be.

As the grower, WE can take control and tip the balance in favor of more lateral branching and a fuller, bushier plant by reducing the downward flow of auxin that suppresses back-budding and allows cytokinin to stimulate buds to grow. We do this by pruning or pinching. In the case of very vigorous material, we can also even go as far as partially or completely defoliating to eliminate nearly all auxin flow and maximize back-budding. This is an important trick in the tool box of bonsai practitioners who use it to increase 'ramification' - the number of leaves and branches. Pruning and pinching simply removes the apical meristem where most of the auxin is produced, which forces back-budding.

Pruning and pinching permanently truncates growth of each branch pruned or pinched. That branch can never extend again. Usually, the first bud proximal to the pruning cut becomes the new branch leader. This is an important consideration because we can use the information to determine the direction of the branch. If we want the branch to grow left, we truncate it just distal (further from the roots) to a left facing bud or leaf - the opposite for right. When you're pruning your branching plants, try to prune back to a downward facing bud. Upward facing buds tend to produce vertical growth and can spoil appearances if allowed to become the new leader.

These practices can be applied to most of the vining or branching plants we grow. Pruning and pinching isn't difficult, and the response is very predictable. The grower just needs to understand the options and be confident enough in how the plant will respond to make a plan and take the leap.

Here are just a few plants with growth habits and appearance were dramatically altered by selective pruning or pinching:

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Al

NOTES:

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clipped on: 09.07.2012 at 02:37 pm    last updated on: 09.07.2012 at 02:39 pm

Trees in Containers III

posted by: tapla on 04.06.2011 at 05:33 pm in Container Gardening Forum

This is a continuation of the second thread on the same topic, both having topped out at 150 posts. You can find a link to the previous thread and the helpful information/conversations it contains at the bottom of this post.

Trees in Containers
A discussion about maintaining trees in containers over the long term

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

If interested, follow the embedded link to the previous discussion about trees in containers.

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clipped on: 09.07.2012 at 02:38 pm    last updated on: 09.07.2012 at 02:38 pm