The right way to transplant that potted blue holly
Q uestion: We have a large pot by our front porch steps with a blue holly growing in it. It’s been in the pot for several years now and I’m worried it’s outgrowing it. When would be the best time for me to repot it? Any suggestions for the process?
Answer: Blue hollies ( Ilex x meserveae ) are really lovely plants. I often recommend them to folks looking for an evergreen that’s fairly easy to grow and tolerant of a bit of shade. It was clever of you to put it in a large container to add some year-round interest to your front entry.
There are many different cultivars of blue holly, each of which has its own merits. For readers not familiar with this type of holly, it’s shrub-like in its growth habit and the leaves are a rich, dark green with numerous spines along their margins.
Like other hollies, an individual blue holly plant is either a male or a female. The males do not produce berries while the females do. In order for a female holly to produce berries, however, there must be a compatible male holly somewhere nearby to pollinate it. It’s recommended that you have one male holly for every three to four female hollies in order to get good berry set. Good partner varieties would be “Blue Prince” with “Blue Princess” or “Blue Maid” with “Blue Stallion.”
While blue hollies grown in the ground will live and grow in the same location for many, many years with few maintenance requirements, your containerized blue holly requires more care. Since it’s doing so well, I’m sure you’re keeping it regularly watered and fertilizing it annually with an acid-specific granular fertilizer, such as HollyTone. Like all evergreens, hollies thrive in soils with an acidic pH. The potting soil likely used to fill your container probably had a more neutral pH, so adding an annual spring dose of soil acidifying fertilizer is even more important than it would be if you were growing the plant in the ground. Don’t overdo it, though; be sure to follow all label instructions on the fertilizer bag and only add as much as they recommend.
As for your question about repotting the holly, when the spread of the unpruned branches reaches beyond the width of the pot by half of the pot’s diameter, it’s time to move the plant into a bigger container. Choose a new pot that’s at least 6 inches wider than the old pot. If you regularly prune the holly (hopefully not into a meatball shape), you may be able to get away with keeping it in the container for an extra year or two, but the root system will still be extensive, so you’ll also have to water more frequently.
Since blue hollies can grow to be large shrubs, you’ll probably have to pot it up into a larger container several times throughout its life span. When moving it into a new pot, tip it out of its old container, and if you discover the roots have circled around inside the pot, cut or saw the outermost roots off to loosen them before planting the shrub in its new pot. While this may seem rough, it’s essential for encouraging the roots to spread out into the soil in the new pot.
Use a high-quality potting soil mixed with a few shovels full of compost to fill the new container. This should be done in the spring. Sometime in late March or April is ideal.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to tribliving@tribweb.com or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.
