They are very vigorous growers and you'll get plenty of lateral growth if you just wait a bit. They are planted very close together so eventually you may find yourself trimming the laterals. You can shear these things or just prune selectively. 10 months is a very short time to be in the ground. After 3 years you'll have a jungle

Thank you Sara, very reassuring. One other question. Does trimming the top growth stimulate lateral growth?

Well yes in that when you remove the terminal buds the laterals will generally 'wake up' but in this case I wouldn't bother, unless you feel like fooling around with it. You can't really hurt this plant!

Thanks again Sara.