lack of hardening off .. should be rather universal rather than plant specific ....

is a pretty simple concept ... not unlike you.. if you decided to sun bathe on the equator.. after a long cold dark winter ... you would sunburn.. and shed the burn skin.. yuck .. lol ..

so a plant will do the same.. if you significantly burn the leaves ... trees.. conifers.. annuals.. perennials..and houseplants .. its all the same .. lack of hardening off to light ...

other than that.. im sure al can hit this one out of the park.. like he presumably did in the prior post ...

most of us.. didnt have the WWW and we just did it ... so i think you are just going to have to DO IT ... no hand holding.. just jump in the deep end ....

ken

It will look ugly for a while. I haven't done it with a fig tree but other plants I've forgotten to move them to back to a shady place as I tried to acclimate them to more and more sun. The power of the sun will burn sensitive tissue whether plant or animal. Skin cancer is always an area of concern but plants usually shed their leaves over time (do they get some kind of cancer from sun burn? I know their trunks/stems can get sun scald)

This happened to one of my tree philodendrons in June 2017 - forgot to move it deeper in shade that day when I took my grandson to my hair cutter to get us both a hair cut. Whoopsie!

This is how it looked last June - when I kept it in more shade. Same pot, same soil for over 30 years now. I may top the soil off every 3 years or so.

Cold often burns my P. bipinnatifidum leaves and the new ones are just fine. BUT, if that didn't happen, there would be many more leaves at any given time. Individual leaves on a Philo can, if not damaged, last for years. So that is not a plant that I would allow to sunburn if avoidable.

This isn't something that can be generalized, best approached on a plant-by-plant basis.

Yes, I've done this with many plants over the years, and many times with F. benjamina in particular. F. elastica takes longer to recover, but the new leaves are gorgeous, worth doing IMVHO. I can't give an anecdote for the other species.

FWIW - last year I moved all my ficus and several other tropical/ sub-tropical woody plants directly from the basement under lights to full outdoor sun, with no attempt to acclimatize the plants to the marked increase in photo-load. As usual, the leaves suffered from photo-oxidation (sun burn) and were soon shed. Even before they were shed, growth of new branches became conspicuous in the axils of most leaves.

I don't think it's important how bright the sun is in any given locale, so long as the plant is genetically programmed to tolerate it's level of intensity. IOW, it doesn't matter if the leaves are burned or badly burned before they are shed, as long as the new flush of foliage is able to tolerate the increased intensity.

I think it's important to understand that branches covered or partially covered with green bark can be affected by and suffer from sun burn. That said, experienced bonsai practitioners work diligently toward helping the plant to maximize the number of fine/ young branches it can produce. For that reason, my trees have a lot of green/ young branches, but they seem to be unaffected by the sudden increases in photo load. That might be because I grow under lights, and the increase in light levels wouldn't be as significant as it would be if my trees were growing in front of a window, but it would seem the fact the leaves burn and branches don't, could be taken as indication branches are less likely to burn.

The idea that leaves will eventually adapt to an increase in light levels needs qualification, because that is not universally true. Something I wrote about leaves' ability to adapt to changes in photo load:

Light Acclimatization

The degree to which a leaf can 'acclimate' to changes in photo load is limited. IOW, you can't expect a leaf that emerged under a full sun light load to acclimate to light levels in a dim corner, any more than you can expect a leaf that emerged in a dim corner to acclimate to a full sun site; this, no matter how long you allow for gradual acclimation. Too, the plant's ability to adapt to higher light loads is greater than its ability to adapt to lesser light loads.

Using a 1-10 numerical example to illustrate (numerical value of 1 is low light, 10 is high light): If a leaf emerges where the light level is measured at 5 units, it's range of adjustment might only be 3.5 on the low side, but 8 to 8.5 on the high side. When the level of adjustment required is greater than what the plant is genetically programmed to deal with, the leaf is shed. Whenever a new leaf appears it will be perfectly acclimated to whatever the photo load is where the plant is positioned (within the limits of what it is genetically programmed to tolerate).

Sun scald is probably not germane to this conversation because it's a winter injury that occurs on a sunny, cold winter days when bark tissue on the warm side of the trunk (usually S or SW in the N hemisphere) are exposed to direct sunlight. The warmth decreases the tissue's cold tolerance such that the tissues are less able to withstand freezing temperatures. At night, or when sunlight is suddenly blocked by cloud cover, the temperature of sap can quickly drop to below freezing over a period of time short enough to disallow bark reacclimation enough to withstand freezing.

Your trees must be reasonably healthy if you want to use this strategy; reason being, they need enough reserve energy to push the newest leaves in the new flush to at least 75% maturity, which is the point at which a leaf can reasonably be expected to be a net producer of energy.

I have found that moving the trees into direct sun w/o acclimation speeds shedding of leaves and their replacement with a new flush of foliage. The net result is, this forces the tree to produce a pristine flush of leaves perfectly adapted to whatever full sun site they find themselves in. The other option would be to try to slowly acclimate the leaves to brighter sun in the hope they won't be shed (and they almost always will be), and live with leaves poorly acclimated to their new position, while the plant works its way through the process on its own.

If I have the time, I typically defoliate completely or partially soon after moving the plants into full sun. The defoliation increases the amount of light and air movement that gets inside of the canopy outline. The additional light and air movement getting inside the outer limits of the canopy has a significant influence on the enthusiasm with which the tree back-buds.

Finally, it's best to get in the habit of doing all hard pruning when you move your trees outdoors or soon after. When you prune, you'll be removing ALL the lanky winter growth that occurred over winter. During the summer, pinch your branches back to 2 leaves after the 3rd leaf has opened. This MAXIMIZES ramification (leaf and branch density), and is the key to a full/ compact tree. Stop pinching in fall. Allow the tree to grow unencumbered by pruning all winter, then prune back to last summer's growth in late spring. If you do this from day one, you'll end up with an entirely different (looking) plant than you would had you allowed the plant to have the lead.

An inosculated (fused)

Ficus benjamina:

Ficus microcarpa:

Pruned June ^^^

Mid - Aug ^^^

After pruning/ wiring ^^^

Ficus benjamina variegata ^^^ 90% of foliage removed

Ficus microcarpa - defoliated

Ficus benjamina "Too Little" ^^^

Al

I didn't believe this stuff when you were telling me 10-ish years ago, but after seeing it, I do, and it makes more sense when reading it now.

Thanks for the moral support, everyone. Seems like I'll be brave and move to full sun once temperatures permit (likely May here in Ontario). They've been in a south-facing bay window all winter and are healthy now so I hope they'll bounce back quickly once defoliated.

Two follow-up questions:

1. Al, you said the following in your post:

If I have the time, I typically defoliate completely or partially soon after moving the plants into full sun.

Do you suggest I let the leaves scald for a few days and then manually defoliate? Or does the above refer to the plant naturally dropping its leaves?

2. Would you suggest moving outside --> hard prune --> defoliate?

Or move outside ---> defoliate ---> (wait a week or so) ---> hard prune?

I had a large Ficus which grew in a NW window in New York. I would put it out in spring on our deck. The deck faced west and was not shaded.

I always pruned it when it went out. My tree was large, over 8 ft. It always made new growth and looked beautiful by the beginning of Fall.

After moving it back inside, it would shed all the extra leaves because of the lower light levels and lack of humidity.

Just wanted to let you know that you will loose leaves going out and coming back in.

Jane

1. Al, you said the following in your post:

If I have the time, I typically defoliate completely or partially soon after moving the plants into full sun.

Do you suggest I let the leaves scald for a few days and then manually defoliate? Or does the above refer to the plant naturally dropping its leaves? I use total defoliation of many species of trees as a way to allow more light and air movement to the bare branches inside of the canopy outline. Removing them a week before they fall on their own benefits the tree and improves back-budding. I also selectively defoliate certain branches as a way of managing energy flow to specific areas of the tree or its branches. Partial defoliation is especially useful when trying to keep the branches in the upper 1/3 thin and twiggy. Fat branches high on the tree and skinny branches low on the tree jars the eye, even if you can't immediately identify that 'something' which doesn't look natural.

Ficus microcarpa, images above and below. The tree was pruned and leaf surface area reduced same day it was brought up from the basement. You can see there is no conspicuous evidence of sunburn yet.

You can even prune all branches back to 2 leaves, then cut 2/3 off of the remaining leaves. When you see back-budding is well under way, finish the defoliation. This might be the most comfortable/ least stressful (for the grower) way of approaching getting the tree quickly acclimated to full sun.

2. Would you suggest moving outside --> hard prune --> defoliate?

Or move outside ---> defoliate ---> (wait a week or so) ---> hard prune? The hard pruning removes the apical meristems where most of the auxin (which suppresses axillary buds) is synthesized, so a hard pruning should be the first step as it's the primary force driving back-budding. Once you see the leaves are burning, you can remove them by cutting through the leaf petiole (stem) anywhere between the main part of the leaf blade and where the petiole attaches to the branch/ stem. The stubs will fall off soon after without any additional action required on the part of the grower.

Al

I didn't put as much thought into it as some of you, but I saw that my attempts to acclimatize my potted figs in the spring usually resulted in them suffering along with leaves dying over a long period. So I just started sticking them out there and letting nature take its course. I figured bright sunlight, water, and fertilizer and there will be new leaves that can take the sun pretty soon. It seems to me that figs drop their leaves and put out new ones for the slightest excuse, anyhow. I don't know that other plants could take that.

Ficus genus has the only members that can handle a sunburn? I disagree on the basis of many contrary observations.

From above:

Light Acclimatization

The degree to which a leaf can 'acclimate' to changes in photo load is limited. IOW, you can't expect a leaf that emerged under a full sun light load to acclimate to light levels in a dim corner, any more than you can expect a leaf that emerged in a dim corner to acclimate to a full sun site; this, no matter how long you allow for gradual acclimation. Too, the plant's ability to adapt to higher light loads is greater than its ability to adapt to lesser light loads.

Using a 1-10 numerical example to illustrate (numerical value of 1 is low light, 10 is high light): If a leaf emerges where the light level is measured at 5 units, it's range of adjustment might only be to 3.5 on the low side, but to 8 - 8.5 on the high side. When the level of adjustment required is greater than what the plant is genetically programmed to deal with, the leaf will be shed before long (usually within 1-3 weeks). Whenever a new leaf appears, it will be perfectly acclimated to whatever the photo load is where the plant is positioned (within the limits of what it is genetically programmed to tolerate).

In the sense that no one can suffer a cut or broken bone w/o sustaining damage, no plant can "handle a sunburn" w/o damage, because the term sunburn or photo-oxidation (synonyms) each imply damage. Too, all plants which are adequately rooted and have sufficient energy reserves to fuel a push at least a partial flush of newly forming leaves to approximately 75% maturity (the 'break even' point where most leaves become net producers of energy as opposed to net consumers) should be able to withstand injury related to sunburn.

Al

I have done this with a number of different plants over the years including some herbaceous carnivorous plants. Some plants can take it, some can't. I don't do this with any of my cacti. They get a bit of a gentler introduction UNLESS spring temps are warm enough. Sun scald on a cactus is damage you will be looking at for a long, long time -- assuming it survives. If spring temps are warm enough, though, I will give them a rather abbreviated "hardening off". But my early spring sun is much weaker than full summer sun and that can make all the difference. Young seedlings, IME, generally just die from a too abrupt transition. Not at all surprising since the tissue of a young seedling is very tender and it does not have the energy reserves to rebuild. (With very young seedlings, they won't even have the right cells to rebuild if they get scorched.)

It's hard to generalize about plants and leaves. Figs can produce buds all over and lots of leaves, but a banana plant just has the growth tip to produce new leaves (not including pups.)

I'm always glad to see more information, as long as it's accurate, so I'm glad for Paul's and Gary's contributions; and, I'm just musing here, not firing a shot over anyone's bow.

My experience is, it's actually much EASIER to generalize, more difficult to be specific, because specificity requires the information provider to qualify the information being offered, which means the info provider must have greater command of the topic. It's easy to say automobiles run on gasoline, but we immediately see the answer is not always true. It would be fine to say most automobiles run on gasoline, however, some are powered by diesel fuel, some by LP gas, some use electricity which is stored in an onboard battery, and experiments are being performed which explore alternate fuels unmentioned herein. The fleshed out statement is well enough qualified to get almost anyone past most would-be critics, which can't be said of the former general and unqualified statement.

A lot can be determined about how well someone knows the subject by the way (s)he qualifies what's being said. Speaking in generalities is often an indication someone wants to be heard, but doesn't want to be held to account for what they are saying. It's safe to make generalizations, then say, "That's not what I meant at all" when content accuracy is questioned.

I'm thinking that when the original post on a thread is narrowed to a discussion about a particular genus/ species those of us providing information specific to the topic probably deserve to be delivered from the obligation to qualify everything said to the nth degree by noting banana, cacti, carnivorous, or a list of plants other than Ficus might not fit the exact pattern as the fig tree.

Even though bananas are monocot herbs, they still back-bud by way of offsets (lateral vegetative buds) attached to the stem, and the morphologic mechanism by which these lateral buds occur has many similarities to the manner in which they occur in Ficus. Sort of like, "same thing, only different", I suppose.

Sun's up - time to get after repotting. Have a good day, all.

Al

Well, good thing I excluded pups!

Strong work, Michael!

The new leaf growth was smaller than I had expected .... That will change. Leaves on trees in the mulberry family (Moraceae), which ficus belong to are genetically programmed so each consecutive leaf on any given branch will be larger than the preceding leaf. Also, the more active primary growing points (nodes) a plant has, the smaller leaves tend to be; this, because the amount of photosynthate produced will be divided by a large number of leaves. Bonsai practitioners significantly reduce leaf size over time by judiciously managing energy flow and increasing ramification (branch and leaf density.

The tree with small leaves being trained as a bonsai started as a cutting from the tree that produced the considerably larger leaf - same genetic material. The difference is all do to culture and manipulation of energy flow.

the ficus elasticas, a little redder in color, Very common in juvenile leaves of a large fraction of species. As leaves mature, the increase in the green pigment, chlorophyll, will mask expression of the purple pigment anthocyanin.

My understanding is I can refrain from pinching any fall/winter growth and instead plan on pruning any such leggy growth next spring/summer when they go back outside. Correct.

Keep us posted re how things continue to shake out.

Al

@tapla (mid-Michigan, USDA z5b-6a) Hi Al, does this technique (abrupt transition, combined with pruning to the 2nd or 3rd leaf) work well with citrus trees too? I have a lime sapling with very few lateral branches that I'd love to encourage to branch out, plus some other young citrus that are very lopsided that I'd like to get balanced out. It's taken me a while to get my citrus to survive in the first place though (had to figure out aa good watering routing with the Arizona summers), so I'm nervous to start chopping away at them

Yes, it will work for healthy citrus trees insofar as using it as a technique to promote ramification ('ramification' = an increase in branch/ leaf density), but keep in mind you might lose some blooms/ fruit if there is a significant loss of foliage. In any potential application of this particular strategy it's important that the tree has enough stored food/energy to allow the first few leaves to reach approx 75% maturity, which is roughly the 'break even point', the point where leaves become net producers of food energy instead of net users. Any reasonably healthy tree should tolerate its grower's use of that strategy w/o any conspicuous negative reaction.

Do make sure your tree isn't badly root-bound if you intend to move a plant from where it over-wintered into direct sun to increase ramification. Root congestion has a limiting effect on back-budding, and when the congestion is severe, it can rob the plant of virtually all growth potential. This means it will work best in years during which you've performed a full repot that spring.

Al

Thanks Al! Two of the ones I want to do this with (including the lime) were repotted out of cycle this year (fall instead of spring) to correct the drainage in their soil (I didn't screen the surface well enough when I made that batch of gritty mix, so I wound up with sludge that impeded drainage). I might wait another year before I take a chop at those ones, to make sure they recover from repotting heading into winter.

I have another one that will be due for repotting this spring though that I can try it on (and I'll be chopping my rubber trees d fiddle leaf next summer - excited to start that process with them!)

(Sorry for e random weird misspelled and double words, for some reason Houzz does NOT like to let be backspace and delete anything...)