managing growth
Elms push out lots of new shoots every spring. If you don't keep an eye on it, the canopy fills up fast, even in places where you don't want any new growth. I try to remove any unwanted shoots as soon as possible, as these can cause swelling and inverse taper.
In my previous blog, I explained how I select shoots in young trees in spring. With this elm, the basic idea is the same, i.e. balancing energy and preventing uncontrolled growth. However, this tree is entering its third year of development, so a little more attention to detail is required.
This tree was collected about ten years ago. 3 years ago, i started building the basic branch structure.
Branch structure
The basic branch structure of this tree is almost set. The primary and secondary branches all have nice movement and taper. This was done by wiring them during spring and cutting them back in late spring, and repeating that process again during the summer months. But more on that in a future article...
For now it's important that I just maintain this primary and secondary branch structure. I basically just want new shoots on the secondary and tertiary branches. The problem is that elms pop out new shoots all over the place. So I have to remove a lot of buds and small shoots that have just started growing.
By removing new growth in places where I don't want any branches, I essentially remove 'auxin' (growth regulating hormone) from that place. As a result, the tree won't grow a new branch in that area and instead 'focus' its energy in other shoots that are left unpruned.
Primary and secondary branches.
'Suckers' emerging from the surface roots.
Shoot and bud pruning
There are a couple of guidelines that you can follow to know exactly which shoots and buds you can remove.
Elms produce so called 'suckers'. These are shoots that usually emerge either straight from the roots of the tree, or from the base. They're called suckers, because they 'suck' (or use) energy that could otherwise be used for new growth in other parts of the tree. These suckers can be easily removed with scissors. Sometimes, they emerge from under the soil line, so you'll have to dig a little and remove them as low as possible.
Another example of growth you should remove, are shoots that emerge at the intersection of two branches. Always try to develop bifurcating branches, i.e. branches that split into two branches. If you leave three or more branches growing in the same spot, this can cause irreversible swelling and appear messy.
In the picture above, you can see two new shoots emerging from almost the same point. You can choose to leave one and remove the other. In this case, I removed both of the shoots, because I didn't need extra branches in that area.
Next you can see another example of a shoot that is growing in a less desirable spot. The small branch next to the orange arrow was removed because it was growing straight under the (primary) branch above it.
If you have a lot of crossing branches one on top of the other, you'll end up with a very messy looking tree. Sometimes you can wire the branch in a new direction and avoid crossing, but in this case it would have looked artificial. So I decided to remove it all together.
Next you can see two shoots that are growing almost opposite from each other, in a place that's already very 'crowded'. Try to avoid this, as this will likely result in swelling.
You can choose to only keep the two opposing branchlets (by pruning back to where the orange arrow is pointing. Or you can remove one of the two opposing shoots. In the latter case, the branches you decide to keep, will be growing in a alternating pattern, which won't cause swelling.
In this case decided to prune of the two shoots all together.
Apical dominance
Elms are very apically dominant. This means that a lot the trees energy is 'directed' towards the top, resulting in lots of growth in the apex. If you don't prune new shoots at the top of the tree, the apex will grow wild and branches will fatten up quickly. This is aesthetically unpleasing, because thick branches up top will look visually 'heavy'. Branches higher up the trunk ideally are thinner than branches that are placed lower on the trunk. You often see this in trees in nature as well. Logically, the lowest branches are the oldest branches, and therefore the biggest.
In the picture below you can see that a lot of buds are emerging in branches in the apex. You can easily remove these by hand or with tweezers.
So, in a nutshell:
- remove suckers from the base and roots
- prune shoots that are growing at the intersection of bifurcating branches
- try to avoid crossing branches
- in a place where lots of shoots emerge close together, prune back to 2 shoots
And that's it for now! The tree is left to grow. When I water my trees, I usually check if there are buds or shoots that I may have missed.
In a couple of weeks, when the first flush of growth has hardened off, I will partially defoliate the canopy, prune some of the upper shoots and then wire the first growth. I will write an article on this mid to late spring pruning, so stay tuned!
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