I believe that they are adventitious roots, triggered by the cuts made along the stem. Root formation, by the way, is the expected response from doing what you did. It’s called air layering.

@HU-579255815 The purpose of notching is to disrupt the polar (downward only) flow of the growth regulator (auxin) that suppresses lateral branching. The notch should be about 1/4" above an existing leaf or a leaf scar (scar that remains after the leaf is shed), and should be wide enough to force the descending growth regulator to flow around the row of leaf buds located immediately above a leaf or leaf scar (in the leaf axil), and it must be deep enough to ensure the entire downward flow of sap through the cambium is directed around the suppressed buds.

The expected response to notching is activation of suppressed axillary buds which is a primary part of new branch formation. Air-layering typically includes various wounding strategies and surrounding the wound(s) with a moist grow medium that helps to stimulate new root growth. Most species of woody plants also respond well to having light blocked from reaching the location where you want roots to grow.

Many species of Ficus typically and prolifically produce adventitious roots (roots that grow from unexpected places on the tree) when grown in a humid environment, but F lyrata is not among them. I suggest you use the tip of a knife or other tool to determine if what you are seeing are root primordia. If they can be removed or scraped off easily they might be a scale insect infestation. If they seem to be directly attached to the tree or they weep sap when you check them, they are likely adventitious root primordia which are the first visible sign that adventitious roots have been formed.

If you provide an image of the entire tree and its pot, I can help you with suggestions or a plan that will allow you to force branching lower along the trunk. BTW - notching to create new branching wouldn't have a definitive effect on growth at/near the top of the tree. Please let us know if you were attempting to air-layer the tree. I didn't see anything in what you said to make me think you were, and the images you uploaded don't show any indication you were.

Al

Thanks for the detailed response @tapla (mid-Michigan, USDA z5b-6a). I'm still not sure I really understand what air-layering is, sorry, but you're correct that it's not what I was trying to do. My aim is to get the plant branching without having to cut off the top.

The trunk lost most of its leaves as it used to be in a different location that didn't get a lot of sun. Since moving it's been a lot happier.

Thank you @tapla (mid-Michigan, USDA z5b-6a). Once again a very helpful response.

I'm happy to prune it back if that's the right thing for the plant. Will that help the trunk to grow thicker?

It's just over a metre tall, the leaves start at about 50cm.

I'm in the southern hemisphere, and we're about to go into summer. The tree is in a north facing window, so gets all day sun, and hasn't hibernated at all during winter as the house does not get cold and it gets a lot of sun.

Thanks again for your help.

I'm happy to prune it back if that's the right thing for the plant. Will that help the trunk to grow thicker? Plants utilize water + carbon dioxide + the sun's light energy to synthesize a simple carbohydrate - sugar, the plant's true food. In a sense, each leaf is an individual food factory. Whenever the plant creates more energy than it can use, it 'grows' by creating new cells that cause the plant to extend and thicken. Reducing the amount of a plant's leaf surface area by removing branches with leaves reduces the plant's ability to make food, so it slows growth/ limits growth potential. Depending on your objective, pruning could be considered to a positive or negative influence, or relatively inconsequential. In that your tree is in good vitality (health) and is approaching the part of the growth cycle where growth potential is maximized by longer days and maximum light intensity, pruning should be seen as a positive in terms of forcing lateral branching, even while it is a negative because it temporarily reduces growth potential.

If it was my tree, I would have no hesitance with regard to pruning it back in mid-Dec, as that timing ensures the tree's most cooperative response and the fastest recovery time. Timing heavy work like repotting and hard pruning to take advantage of your tree's strongest growth period, while making allowances for weaker periods of growth by minimizing pruning and avoiding repotting, makes absolute sense because it minimizes lost potential.

If you have an idea of what you want the tree to look like, please describe it and I can help you with a plan to achieve your goals. There is nothing like having a plan that prioritizes plant health and incorporates the work required to meet your design objectives.

Al

Hi @tapla (mid-Michigan, USDA z5b-6a), thanks again.

I will wait until mid-December to prune.

In terms of shape, I'm hoping for something branching but not too wide (I've added some pics as an idea). And, of course, hoping to strengthen the trunk. We have 3m ceilings so if the plant ever gets close to that tall it will need to be stronger at the bottom.

Thanks

When a plant grows, secondary growth (thickening of branches and the trunk) is a given, and the amount of growth is closely related to photo load (light intensity and duration) and collective leaf surface area. Other cultural factors like temperature, nutrition, and conditions in the root zone (air:water relations) are also important factors, but as long as the tree is healthy they are not as significant as light and leaf surface area, but do make sure you're fertilizing regularly with an appropriate fertilizer. Ask if you need guidance, ask any questions that aren't answered in this post I uploaded re Care for Ficus in Containers.

There are 2 ways to promote back-budding that results in new laterals (branching).

1) You can move the plant outdoors into a sunny spot and fertilize at luxury levels when nights are reliably above 13-15*C, or move the plant in and out when/as temps allow. The increase in light and increased air movement which increases the speed of the nutrient stream promotes back-budding and increases growth rate. Flexing of the trunk and branches stimulates enhanced production of a naturally occurring polymer (lignin - it makes plants woody) which adds thickness and increases strength.

2) Timely pruning actually forces the plant to back-bud, and it's the 'timely' part that adds to how enthusiastically the plant responds.

Because your tree is so short, the only pruning you will need to do is pinching (unless there is NO branching and you want to force new branches). Pinching consists of removing the branch terminal bud. I described the hormonal disruption that pruning causes and why it forces back-budding in one of my posts above.

This is a rooted Ficus microcarpa cutting that was pinched back to 2 leaves. The 'pinch' has forced a new branch to form in the leaf axil (crotch between branch and leaf stem). When these new branches have extended to the point where the third leaf bud on each new branch is starting to open, I'll pinch those branches too. So, I pinched the trunk to get 2 branches. After pinching the 2 new branches back to 2 leaves, I'll have 4 branches. Another round of pinching wile yield 8, then 16, 32, 64, .... . Soon, this cutting will be very full, full enough that I'll need to start thinning branches to let more light into the middle of the canopy to prevent leaf loss, a good place to be.

This is a coleus that has a trailing/ hanging habit, that was judiciously pinched to specifically increase branch and leaf density, so you can see that pinching is a very useful tool.

Another:

A young, dormant Zelcova serrata that was pinched early on to increase branch and leaf density. You should be able to make out the hundreds of new buds on the branches, every one of which will be a new branch:

The trunk is about 9cm thick and the tree was not quite 3m when I cut it back.

You can see I have a lot of experience manipulating plants in order to maximize branch/leaf density (ramification). Hope you enjoyed the images.

Al