|why are my inkberry leaves turning yellow-red? It is also
in a plastic recycling container.
|The leaves on your Ilex glabra should not be turning color at all, it is an evergreen with a consistently green foliage. (Some cultivars make take on a purplish tinge in winter but it is too early for that to happen yet.) Unfortunately, based on your description I am not certain what is happening -- there are many possible causes.
I hope you used a good quality potting mix formulated for container plants when you planted it in the current container and that the roots have grown into that potting mix. If not, it may be rootbound and/or suffering a lack of nutrients and/or water as a result of that.
This is a plant that needs consistently moist, acidic soil, so make sure you are watering it enough to keep the soil mix evenly moist throughout -- but not sopping set and never dried out. Also make sure the drainage holes in the bottom of the container are open and draining freely to avoid overly wet soil.
Nutrient deficiency can also cause color change in some cases. A typical sign of lack of nitrogen can be yellowing and a sign of lack of phosphorus can be red along the margins of the leaves. This type of symptom however is very difficult to diagnose long distance. I would suggest you work with your county extension to determine specifically what is happening so you can take steps to correct the problem. You would need to be very careful about making this type of correction at this time of year because excessive fertilizing could cause a late season growth spurt that would not harden off in time for the winter, thus causing excessive winter cold damage to occur.
I should mention that it would be much better for this shrub to be planted in the ground. It will have a difficult time surviving the winter outdoors in a container where the roots are not as well insulated as they would be planted underground. And, planting it in prepared garden soil would probably help solve any possible nutrient problems. This might be something to discuss with your local expert as well.
Best of luck with your inkberry holly!