I am a physical sciences guy. What is this 'energy' you refer to?
To me energy in trees is carbohydrates produced in the leaves by photosynthesis. These get used and stored by living cells throughout the tree. Trees are not potatoes.
But more to your question, all those white ends tell you that the roots are growing and that your tree presently has a high capacity to (re-)grow roots. So now would be a good time to comb them out and prune them so your ligustrum will grow more vigorously afterward. The possible issue is that cutting all those roots will seriously limit the water supply to the leaves that is needed to transport water and minerals essential to photosynthesis. So the leaves can and do respond by closing their stomata to slow down the rate of transpiration. Ligustrum has waxy-leaves and will effectively do this, unlike maples, say, that lack the waxy cuticle and will continue loosing significant moisture through the leaf surfaces. Still, if new growth is not extending, one can repot maples now but will need to sprinkle to the foliage from time-to-time through the day for a week or two.
Trees and roots harden to cold by being exposed to temperatures dipping below freezing overnight and then colder over the span of weeks, like what usually happens in fall. During the 4 or so weeks it takes for the roots to recover, they are vulnerable to hard freezing (soil temperatures below something like 20F/-5C say). Hence one should should not repot any later than about 4 weeks before the first frost date in their location. You are in the vicinity of Leeds is USDA zone 9a, so I think you can safely repot until at least mid-Oct and probably mid-Nov, in this respect.
New growth extends by water being osmotically drawn into the vacuoles of new cells --> in other words, it requires a lot of water. So root pruning is not advisable when new growth is pushing/extending.
Assuming your ligustrum is NOT pushing new shoots presently, now is a good time to repot, IMHO. The way I suggest that you do it is
- cut the bottom 25% to 33% of the root-substrate 'plug' off - pruning scissors should do the job, but one can also use a saw
- loosen the roots from the perimeter of the plug and prune away the loose ends
- comb the substrate/soil from the roots, roughly one-inch into the plug from its sides, using a root hook or chopstick.
- turn the pot upside down and sit your tree on it. Use this as the template to cut the roots stick out of the combed perimeter. If the plug is bigger than the base of the pot, repeat step 3 until it is about the same size or a smidge smaller, then prune the roots that you've combed out.
- put the trimmed plug aside after spraying it with water or dunking it in water or covering it with a damp towel, so as to keep the roots moist.
- clean your pot, replace the drain screens if needed, and thread in new wires to hold your plant.
- put new substrate in the bottom of the pot to the depth that is needed for your tree to be properly potted - sit the tree in the pot and confirm.
- set the tree aside and make a peaked pile of the substrate in the pot, centered.
- put your tree on top and wiggle it back and forth while forcing it downward (hands on the plug!) until it again sets at the proper height
- loosely twist down the wires and make any fine adjustments in the tree's position in the pot before twisting the wires down tight.
- grasp the twist with pliers, pull up and release the tension as you twist down - rinse and repeat until the tree doesn't wiggle in the pot.
- progressively fill the perimeter with substrate, occasionally thrusting your chopstick toward the bottom of the pot and wiggling it so that the grains fill all the spaces around the roots.
- water, put your tree back where it is normally kept and patiently be alert to any adverse signs (droopy foliage, for example). You should only need to be patient while keeping it properly watered (a big less than was usual before).
The last thing I wish to say, is that one can kill an evergreen tree just as easily (or maybe even more so) in spring as after the passage of the summer solstice. The key is not overdoing the root work, regardless of when you choose to repot.
so I did in fact trim more off than what's pictured... Thanks!
I was hoping to get some resistance but got the opposite. I thought patience was supposed to be a virtue.
