I purchased a gallon size Japanese Holly (Ilex crenata ‘Sky
Sentry’) 5 years ago and put it in a 12″ diameter container. It has
not grown much, and has been looking bad lately, so I thought it
was probably root bound. To my surprise, when I took it out, there
were no new roots–the root ball was about 3″ deep and 6″
across. Is this a normal root for the Ilex? What does it need to thrive?
Since you mention that the plant is not looking healthy, I wonder if it
may have root rot.
According to North Carolina Cooperative Extension, Ilex crenata is
highly susceptible to this fungal problem.
It is possible that there are nematodes feeding on the roots and
diminishing the plant’s ability to get water and nutrients from the soil.
The Organic Gardener’s Handbook of Natural Insect & Disease Control by
Barbara Ellis (Rodale, 1996) says that holly roots grow close to the
surface, so perhaps the size of the root ball is not abnormal.
Missouri Botanical Garden has general information on this plant.
To determine what exactly is causing the plant’s ill health, you may want
to bring pictures and samples of the affected parts of the holly to a
Master Gardener Clinic.