Question
I'd like to grow a Sky Pencil-jap. Holley in a container.  I live in northern N.J. so have pretty cold winters, -10, rarely -15.  Can I grow this in a container and keep outside through winter?  If so, what size container and how often would I need to repot or cut roots back?

Thank you,
DW

Answer
Sky Pencil Holly (Illex creneta) is hardy only to a zone 7 (-15 degrees) ?so probably better along the coast of New Jersey, however, container grown plants can be better protected, because you can move them around if it REALLY gets cold.

http://www.usna.usda.gov/Newintro/skypenc1.html

Lots of varieties are available:
http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/cultivars/ilex_cre...

As to size requirements, these varieties range from 3 to 10 feet wide, so the root ball is about 1/3rd of that, or ultimately 1-3 feet around.  Also depends on how big a plant you start with.  Obviously, with a bigger pot, no re-planting would be required...and maybe some opportunity for added interest with some perrenials or draping additions like Virginia creeper or cascading annuals.

At a minimum, you'll want a container that is bigger than the bucket the plant comes in, by a factor of 1/3rd, so a pot that is 1 foot wide, needs a pot that is 16 inches across...And add a bit more room if you plan on adding those perrenials.

There is no magic requirement to re-pot every x number of years; if it is overcrowded, performing poorly, or rootbound, put it in a bigger pot (or fertilize!).  If it is doing o.k., leave it alone for another year.

Hope it helps
~M