Seiju Elm not leafing out

I have had this Seiju Elm for three plus years.  I have never been able to get a full canopy of leaves.  Internodes are way too long.  I repotted it two years ago and will repot it again this Spring.  Tree is healthy, pest free and in well draining bonsai soil.  It gets plenty of light and water.  I don't know what else to do in order for this tree to fill out.  Any suggestions?

Thanks

Is this plant getting a full winter dormant period? In your profile location, what do you mean by zones 7 and 10? Nothing in zone 7, where I am, is even close to budding out. If this plant is being moved between zone, it is most likely confused physiologically, by having severe swings in temperature or sunlight.

Aside from that, there could be a number of factors causing/contributing to the lack of vigor. It could be that your plant needs more sun. For some reason people tend to baby these dwarf elm cultivars. They will take full sun all year where I am. When was it last repotted? Smaller ones like this can be repotted every year. Elms also like pots that are a little on the deeper side. Are you fertilizing sufficiently?

I concur with all recommendations, and will add the following:
- Feeding. Fertilizing regularly during the growing season?
- The structure of this tree looks pretty good, but it needs more development. It looks like you've got too many '3's and 4's growing from your axials. Trim down to 2 branches on each branch junction, and let 'em grow long to fatten the branches up properly and develop taper before cutting. (Hedge pruning)

Hi Jaybird.

As stan has already said, it would be helpful if you clarified where you live on your profile. A basic country and state is good enough to get more tailored responses back. Putting in zones as well is fine but remember, zone classification can vary from country to country.

Thanks

Thanks to all for your informative responses.

I should have explained that my tropical trees and I spend 6 months of the year in Virginia (summer)and the other 6 months (winter) in Florida. I may have the wrong info on this elm as I've never left it in Virginia for the winter months, ergo it's not gone into full dormancy in the past few years.

I will leave it in the "north" next winter so it goes through a dormancy cycle. In the mean time I will prune it back to the secondary branches, repot in the spring and give it plenty of food come the growing season.  

 

As I understand it, some Chinese elm varieties do grow well in Florida, and do not require dormancy. So that may not be your problem. However, I have noticed with my elms that following winters where they behaved as semi-deciduous (mild winters), growth is not as vigorous as after winters where all leaves are lost. Just an observation from my experience, in my particular climate.

What time of year do you go south? If your plant is in VA in late September or later, it is probably already preparing for dormancy based on the length/intensity of sunlight, which triggers hormonal changes in the plant. Moving it after it begins senescence will confuse the tree (can you say raging hormones?). I think this is most likely your problem.