I probably would have done it over the course of several (2-3) repotting sessions at 1 or 2 year intervals. As you already mentioned, root pruning young trees well before they get to the point where a major major pruning is required is much to be desired.

I had imagined it,

How is your tree faring at this point in time?

Incredibly the tree seems to be doing well and is losing a few leaves (in the photo the leaves it has lost in the last 24 hours).

In fact today I potato it but just a little:

Should I prune it more even if it doesn't lose many leaves?

However, another ficus benjamin whose roots I pruned is not doing well. Now I'll put you some photos of this second plant in this discussion: https://www.houzz.com/discussions/6449925/ficus-benjamin-suffering-after-root-pruning Please help me!

I have more questions for you.

1. This winter several leaves have taken on this appearance (yesterday I removed one part and today another): does it depend on root congestion?

2. When you want to eliminate leaves with this appearance, is it better to cut the branch or eliminate the single leaf by making the cut at the stem level and leaving part of the stem itself?

3. Should I also prune this ficus hard even though it loses much fewer leaves compared to the other plant (https://www.houzz.com/discussions/6449925/ficus-benjamin-suffering-after-root-pruning#29107750)? I have pruned little so far: this amount of leaves today and a similar amount yesterday.

So far I have shortened all the thin branches of the upper third of the plant to 2 leaves. Is this okay or should I be more radical and also cut the thick branches, eliminating everything above the line?

Put the tree in shade

While I wait for you to answer the questions I asked in the previous post, I'll add another question. Does a repotted ficus have to be in the shade even if it is used to being in the sun? How many days must it remain in the shade?

While waiting for you to answer the questions, I'll update you. Although I pruned the plant a little (see what I wrote above), this ficus suffered much less than the other one (https://www.houzz.com/discussions/6449925/ficus-benjamin-suffering-after-root-pruningand) and would say it is fine after 40 days from pruning its roots. Who knows why it suffered less than the other ficus: if I pruned the roots less (I don't think so) or if the plant was better than the other one when repotting.

1. This winter several leaves have taken on this appearance (yesterday I removed one part and today another): does it depend on root congestion? It's difficult to say. It does look like it could be a nutritional imbalance or deficiency of one of the mobile nutrients. I don't think it woulds be N or Ca because of the nature of the symptoms, more likely P or K., if it even IS nutritional. If roots are congested, that COULD cause it, as could a high level of EC/TDS (salinity), skewed nutrition ratios, or over-watering.. There just isn't enough info to offer anything more definitive.

2. When you want to eliminate leaves with this appearance, is it better to cut the branch or eliminate the single leaf by making the cut at the stem level and leaving part of the stem itself? If it's a branch affected by an infectious contagion, it's best to remove the branch if multiple leaves are affected, but that leaves the question of how much faith you have in the accuracy of the diagnosis. If it's a random leaf you suspect of being diseased, snip through the petiole (leaf stem) close to its attachment point with a cutting tool. The remaining stub will fall off within a week or two after snipping the leaf. Avoid pulling leaves back toward the base of the branch they are attached to. If you must PULL a leaf off, pull it toward the tip of the branch to avoid injury to axillary buds common to pulling leaves off in the wrong direction. When you have removed enough leaves over time, you'll gain a sense of which leaves are ready to abscise on there own and can be dislodged with a light tug and which leaves should be snipped. If any resistance is met or you are in doubt, default to snipping through the petiole and allowing nature to finish the job.

3. Should I also prune this ficus hard even though it loses much fewer leaves compared to the other plant (https://www.houzz.com/discussions/6449925/ficus-benjamin-suffering-after-root-pruning#29107750)? I have pruned little so far: this amount of leaves today and a similar amount yesterday. If your plant loses leaves after you have completed a full repot, it is usually related to a die-off of fine roots due to desiccation, or a volume of roots large enough to ensure the root system lacks volume enough to keep the entire canopy canopy hydrated. When this occurs, the easiest fix is to prune back the canopy to a volume the roots can keep adequately hydrated. You can also raise humidity (greenhouse, tenting, etc.).

There are times when pruning the canopy should be used to balance the root to shoot ratio to avoid wholesale shedding of entire branches or even total collapse of the entire organism. Weak trees that are weak due to root congestion and the accompanying dearth of resources that accompany the congestion are at higher risk than trees (with congested roots) that are not circling the drain. It's not good to do a hard repot to pull a tree back from the brink unless you're reasonably sure the tree's level of vitality is such that the tree can tolerate it.

Other times, whether or not you should prune back the top is a matter of esthetics, your personal preferences, and your vision of what you want the tree to look like. IOW, sometimes it's nearly mandatory for the good of the tree to prune the canopy hard, and other times it's an option removed from concerns about vitality or development.

Sometimes a sick tree needs to be brought back to a higher level of vitality before a full repot can be performed. Usually though, the young trees you're working with will tolerate a LOT of adversity because they are nearly all living mass and as such, very resilient. They might not want to get up and dance after working roots hard, but when they do get over their pouting, they'll put their approval of your ministrations on display.

So far I have shortened all the thin branches of the upper third of the plant to 2 leaves. Is this okay or should I be more radical and also cut the thick branches, eliminating everything above the line? Whenever I repot an apically dominant (AD) tree, I always look for opportunities to thin the top by removing as many large branches as possible in the canopy. You can always rebuild the top of an AD tree in a very small fraction of the time it takes to bulk-up the lower branches. In large part, keeping the canopy relatively thin and twiggy results in thicker lower branches because the lower branches then get more light and air movement which increases back-budding and leaf density on lower branches. Thinning the top does slow down trunk thickening, but learning to use sacrificial branches low on the tree can make up for keeping the top thinned.

Does a repotted ficus have to be in the shade even if it is used to being in the sun? How many days must it remain in the shade? Some trees, even after a hard repot can go right back out in full sun, like pines and junipers. How severe the rootwork was is the key determining factor, that, and weather conditions. I build about 10m of bench space at the back of my garage where I can move trees that do poorly in full sun when temps are high, but it's primarily for broad-leaf evergreens after a repot. My protected area has a very tall hedge (6-8m) on the east side and my garage blocking sun on the south side. This is called open shade, which is full shade with open sky above. All trees in leaf other than succulents and conifers are sited there until I see new growth. Typically that occurs within a 1-2 week period after the repot, depending on severity.

The strongest energy sink a tree has o/a is respiratory function, i.e. to maintenance of living tissues. The strongest growth related energy sink is production of fine roots. The tree's systems are such that the tree's first order of business will be to ensure there are enough fine roots to provide essential resources to to existing viable organs. If there aren't, the tree will shed organs until the roots are able to service what viable tissues remain after the shedding. Only then will top growth resume. Keep in mind that, because you see a new leaf growing or a branch extending, it doesn't necessarily represent true growth. True growth is a measure of the increase in the dry weight of the tree's living mass; so, if the tree is shedding parts to secure resources for new leaves and branch extension, the dry weight of its viable mass could very well be decreasing.

Does that cover all your questions?

Al

All clear, thank you dear Al. Any tricks to further thicken the lower branches indicated by the arrows and to ensure that they remain thick over time? Simply pinch them? I like the current appearance and the fact that the lower branches hide the pot.

Still on this same topic (thickening of lower branches). This is another plant and its lower branches are thick but bare: they have a few leaves at the end of each branch. Is there a way to get them thickened? How? Pruning the upper part of the plant created new lower branches, but the older, thicker ones remained bare.

Often, keeping a tree healthy and the thickness of branches natural looking comes at the price of the o/a composition temporarily looking awkward. To ensure lower branches retain a high level of vitality, avoid pruning them and thin/restrain growth of the foliage above the weak branches. Too, use of sacrificial branches growing straight upward on the trunk or branches are removable and help to ensure the thickening of the trunk and branches as well as the vitality of lower branches. Here is a Ficus natalensis with a single sacrifice branch, the sole purpose of which is to thicken the trunk and provide more rapid trunk taper:

The branch is strategically located on the back side of the tree (its least appealing viewing angle). The tree will not go into a bonsai pot until the branch has been removed and the wound is well on the way to healing.

Below is a Ficus microcarpa. You can see, just below the top that a sacrifice branch (to increase thickening and taper) was removed. The radical decrease in taper that jars the eye will disappear in a year or two, making the taper very natural.

This is a Carpinus coreana (Korean hornbeam), I've been working on for 5 years:

I decided the composition would profit from the thin bottom branch moving right, but there is obviously significant difference in thickness between the 2 branches above it. The fix is, allow that branch to grow unencumbered by pruning until it is slightly thicker than the low branch attached slightly lower on the tree and moving left. Notice how the top of the tree has been restrained via pruning, forcing energy to the lower branches. This tree was just pruned a week ago. Strong back-budding is occurring and I will direct 2-3 branches growing straight upward off the top of the thin branch moving right in order to hasten thickening.

[This tree's] lower branches are thick but bare: they have a few leaves at the end of each branch. Is there a way to get them thickened? How? Pruning the upper part of the plant created new lower branches, but the older, thicker ones remained bare. Only if the reason for the foliage being concentrated at the branch apices (tips) isn't cultural. Root congestion causes much shedding of foliage proximal to the apices, leaving the tree with a 'poodle' or 'pompon' look.

A fair amount of the he growth regulator auxin is produced in immature leaves, so unless you're using a branch in a position you don't want a branch to grow as a sacrifice branch, it should be rubbed off as soon as it occurs. If the branch doesn't respond to additional light and air movement (which increases the flow rate of the nutrient stream via an increase in the rate of transpiration) within a week or two, look to nutrition, root congestion, or soil compaction as cause for any dearth of back-budding.

Al

@tapla (mid-Michigan, USDA z5b-6a), bad news! Here is the plant as it appeared at the beginning of August:

Here is the plant as it appeared at the beginning of November:

What happened? In August I forgot to water it (in that period I water every 7-8 days and instead I watered after 15-16 days). Since then it started to lose a lot of leaves. To give you an idea, this is the amount of leaves that fell every 2-3 days.

I thought it was due to the lack of watering, but the plant continued to lose leaves for 3 months and only at this point I realized that there was a massive infestation of red mite (I don't know if it is Tetranychus urticae; an old professor of photopathology explained to me that it could also be related species/races).

I take this opportunity to make some considerations and ask you for some advice.

The considerations. Perhaps not watering the plant weakened it and favored the attack or the parasites were already present (if you read above I showed a lot of stained leaves) and with the heat they multiplied. However, I have the impression that pruning the roots makes the plants more susceptible to infestations and not because it weakens them. This ficus was in full recovery and had suffered very little after pruning and yet it developed an infestation that I had never seen before. I read that protective substances start from the roots: https://pubmed.ncbi.nlm.nih.gov/27683726/ . Plants do not have an immune system and therefore my comparison is perhaps inappropriate, but it is as if there was an immunological memory in the roots.

The advice. I have read what you wrote here. While I wait for you to answer the questions I asked you, I would like to ask you some more.

1. Why do you recommend water + isopropyl alcohol rather than an insecticide? I ask this because I have seen that propyl alcohol is not so easy to find (it is often found at 99.99% instead of 70%) and 1 liter costs about 10-12 euros. In short, it does not seem easier to find or cheaper.

2. I had thought of buying either abamectin or hexithiazox but I think that here in Italy you need a sort of license to do so.

3. A few days ago I used an insecticide spray (Bayer Raid): it is for flies and mosquitoes and contains Prallethrin 0.1g, and 1R-trans-phenothrin 0,125g and does not damage plants (it is written and I have already used it for aphids without damaging the schefflera). The problem is that I read that mites can be resistant to pyrethroids.

4. In various forums and web pages it is recommended to use white mineral oil. Even the professor of phytopathology advised me to use it. Although I do not like mineral oil because it gets very dirty (in a courtyard it is not a problem, but on a terrace it is), I would be tempted to use it if only because I have it (Oliocin by Bayer). What do you think? Do you think it is effective? It acts by suffocation. Do you think it could damage the leaves? The water with the oil inevitably ends up in the soil: does the oil not harm the roots?

5. How do I know if a treatment is effective? I'll explain what I mean. If you do not use a method that also involves the use of water to mechanically wash away the parasites, how can you understand if they are dead? Simply because you no longer see any moving?

6. Another interesting topic. I was asking the professor of phytopathology what the infestation threshold was beyond which to proceed with treatment. I'll try to explain better. Once I discovered this massive attack, I inspected other ficus benjamin that are not inside the same room but outside (it's my doctor's office) or at home. And I discovered that there are other infested plants but with much fewer parasites: on some there is one every 10-15-20 leaves. I wonder then if these plants should also be treated and if the few leaves that fall (they seem to be apparently healthy plants) fall due to the presence of a few mites. I think the professor gave me the right answer: "the intervention is considered justified when a threshold called economic damage is exceeded; however, yours is an ornamental plant on which there is no threshold/damage determination (floriculturists usually tend to intervene only on the presence) so everything depends on the affective factor and the time and desire available". In other words: if you have time and want your plant to look its best, you need to intervene even if there are very few parasites. @tapla (mid-Michigan, USDA z5b-6a), do you agree? If so, then it is necessary to find a treatment that does not limit itself to containing the number of parasites, but that is able to exterminate them all. Are isopropyl alcohol and the various methods I have listed (spray conteining Prallethrin 0.1g + 1R-trans-phenothrin; Oliocin by Bayer; abamectin; hexithiazox ) able to kill all parasites?

propyl alcohol is not so easy to find (it is often found at 99.99% instead of 70%) and 1 liter costs about 10-12 euros. In short, it does not seem easier to find or cheaper.

Even though it's been almost 6 months, I hope you'll answer me. I'll add another question: is it possible to use denatured ethyl alcohol instead of isopropyl alcohol? I'm asking because here in Italy isopropyl alcohol is more difficult to find and costs several times more than isopropyl alcohol. A friend of mine says that you Americans recommend isopropyl alcohol because in the US isopropyl alcohol is easy to find and denatured ethyl alcohol is not (I don't know if he's right). I read that teryl alcohol doesn't damage the plant: https://academic.oup.com/pcp/article/63/9/1181/6674685?login=false. However, I don't know if it can damage the leaves and if denatured ethyl alcohol can cause damage compared to non-denatured alcohol.