How aggressively you CAN root prune depends on your tree's stored energy level. Heavy root pruning of a weak tree can be damaging or disastrous, while root pruning a healthy tree while it's growing robustly can usually be done with impunity if follow-up care is appropriate. As you know, the best time to work your (tropical ficus) tree hard is early summer. There is a window between Father's Day and Independence Day that in which I do as much repotting of houseplants and tropicals as possible.

Root pruning isn't an all or nothing affair. I've been working on the roots of a Taxus (yew) as a bonsai for more than 8 years, trying to reduce a very deep root system to where I can get the tree in a bonsai pot. The top makes a very impressive bonsai already because I've been working on its refinement, but a plastic clothes basket doesn't meld with the tree in harmony as attractive as a discerning eye might demand. The point is, it's often better to consider the viability of the tree and work in stages than to shoot for the moon in one fell swoop.

I'd set some time aside to bare root, and I'd keep at it until you accomplished that worthy goal. Future repots will be easier, and leaving the hardened soil only assures a limited tree.

Here is something that explains the seeming paradox about why plants need air in the soil. I'm copy/pasting from something I left on another thread, but it should still offer an understanding:

Though roots form readily and often seemingly more quickly on many plants propagated in water, the roots produced are quite different from those produced in a soil-like or highly aerated medium (perlite - screened Turface - calcined DE - seed starting mix, e.g.). Physiologically, you will find these roots to be much more brittle than normal roots due to a much higher percentage of aerenchyma (a tissue with a greater percentage of intercellular air spaces than normal parenchyma).

Aerenchyma tissue is filled with airy compartments. It usually forms in already rooted plants as a result of highly selective cell death and dissolution in the root cortex in response to hypoxic conditions in the rhizosphere (root zone). There are 2 types of aerenchymous tissue. One type is formed by cell differentiation and subsequent collapse, and the other type is formed by cell separation without collapse ( as in water-rooted plants). In both cases, the long continuous air spaces allow diffusion of oxygen (and probably ethylene) from shoots to roots that would normally be unavailable to plants with roots growing in hypoxic media. In fresh cuttings placed in water, aerenchymous tissue forms due to the same hypoxic conditions w/o cell death & dissolution.

Note too, that under hypoxic (airless - low O2 levels) conditions, ethylene is necessary for aerenchyma to form. This parallels the fact that low oxygen concentrations, as found in water rooting, generally stimulate trees (I'm a tree guy) and other plants to produce ethylene. For a long while it was believed that high levels of ethylene stimulate adventitious root formation, but lots of recent research proves the reverse to be true. Under hypoxic conditions, like submergence in water, ethylene actually slows down adventitious root formation and elongation.

If you wish to eventually plant your rooted cuttings in soil, it is probably best not to root them in water because of the frequent difficulty in transplanting them to soil. The brittle "water-formed" roots often break during transplant & those that don't break are very poor at water absorption and often die. The effect is equivalent to beginning the cutting process over again with a cutting in which vitality has likely been reduced.

If you do a side by side comparison of cuttings rooted in water & cuttings rooted in soil, the cuttings in soil will always (for an extremely high percentage of plants) have a leg up in development on those moved from water to a soil medium for the reasons outlined above.

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You can skip the rooting hormone and fungicide if you want. They're not necessary. I do use a little Superthrive (for its auxin) as a root soak after repotting, though. I've done some experimenting with loose controls in place and while it has proven useless as a 'tonic', it is effective at stimulating root growth and root division. I fill a tub with water and a little Superthrive & fully saturate the soil in the tub immediately after repotting. Securing the plant to the pot so it can't move in relation to the pot fractionalizes the time it takes for the tree to establish in its new digs, too.

Al

Thanks Tapla, i appreciate the advice. I took it easy on the rest. I am interested to see what happens to the first few, because man I really chopped them up, and they weren't that healthy to begin with. It will be an interesting experiment. I'll try to remember to come back on the forum in a month or two and post the results.

They grow from cuttings so they should tolerate very aggressive root pruning, but thin the leaves aggressively too to help balance the water demand.

If you have ever lived where F. b. grows outdoors you would believe that nothing can kill them . . . or outgrow them. I used to saw/fight/hack 15-20 feet of vertical growth and 30-40 foot of spread every year or two at an old relative's house Lat. 26 with 55 inches of annual rain.

That a tree is cooperative when trying to propagate from cuttings isn't a good indicator of how aggressively you can be about root pruning. How robustly the plant is growing and where the plant is in the growth cycle go hand in hand as determinant factors, along with how much stored energy there is in roots/cambial tissues.

Staggering work on the canopy and leaves is much preferred to "balancing" the amount of roots:shoots removed at repotting time. Leaving foliage untouched when you repot provides the significant benefit of contributing much more current photosynthate than if you'd removed the foliage. The plant then relies much less on it's energy reserves to reestablish in the pot and more on current energy production, which means you end up with a much stronger tree. If the top needs a hard pruning, it should be done 2-3 weeks after the repot, when the plant is robustly pushing new growth. Repot Father's Day - prune canopy 4th of July is an excellent plan and an easy way to remember favorable scheduling for repotting your tropicals (not F carica).

Al

Tapla, thanks a whole bunch, I’ve been doing some remedial reading on tree planting cultivation, in particular Benjamin Ficus, your articles gave me some heads up considerations, thankyou. I’ve got a Benjamin ficus potted at home. I use to foliage and root prune it every three to four years, its way over due now…had a bad experience with some folk who attempted to poison all my house plants…that’s a long story I sooner like to avoid talking about. I have a form of Ficus tree that is weeping, it took two years to recover from these diabolical folk poisoning plants, which I did nothing but let it grow for four years to recover it’s former beauty. I’m going to take your advice on fathers day, and since July is my birthday month, I think I’ll get my old Weeping Ficus Tree back again. Just a heads up, I use charcoal in my soil mixes on the potted soil surface, along with a two inch layer of peat mixed with wood chips and a touch of cows manure. I do this in order to create a natural soil colloidial break down of natures food for the tree, in this way avoiding harsh chemical foods. Also, when I repot the tree, I don’t let the layer of wood chip compost/mulch surround the crown of the tree…but I do add a little extra charcoal in that area to control root rot…and the plants love charcoal in their soil anyway, you can really see it when the tree begin to grow new foliage, plants love Carbon. I try to imitate the floor of a natural forest with my potted trees…reading ‘Silviculture Ecology’ is real interesting, soil management seems to be the big emphasis in this book, which I find helpful and supportive in potted plant cultivation.

I appreciate your kind comments very much, but hope you don't think I'm unkind when I mention a couple of things that came to mind as I read your comments.

First, a plant's carbon needs are fully satisfied by way of the CO2 they utilize to form hydrocarbon chains during photosynthesis. While I don't think there is any significant disadvantage in using charcoal in your medium unless it's of a size that's inappropriately coarse or fine, neither do I think there is any significant advantage. Essentially, on a size for size basis, charcoal and perlite perform about the same function in media. Charcoal should probably looked at more for its physical properties than any chemical considerations.

Then, if we could call the nutrients plants take up 'food' rather than what they are - the building blocks plants use to grow and keep their systems orderly, we would be able to say that a plant's diet consists of salts, which are the product of an acid:base reaction. When all is done, the salts supplied in a container of MG or other soluble synthetic fertilizer are exactly the same salts plants use from the end product of decomposing manure. The main difference is, we have tight control over what our plants get, how much they get, and when they get it when using soluble synthetics, something we can't say about using manure or other types of organic sources of nutrients that depend on the activity of soil organisms, the populations of which go through boom/bust cycles in containers. It's this boom/bust cycle that makes it impossible to depend on plants getting what they need, when they need it in containers if they depend on organic sources of nutrition.

Whatever your course, I hope you fare well by it. Good luck, Ivan.

Al

There is no doubt that photosynthesis is as important to life on earth as oxygen. W/o photosynthesis, we would have neither plants nor the animals that feed on plants to consume for the energy therein contained. We'd be a bunch of starvin' pilgrims in no time at all.

Take care.

Al