Behind the Variety: A Gem of a Holly

Jennifer Polanz

The hybrid Emerald Boxer Holly from Monrovia is part of Dr. John Ruter’s breeding program at the University of Georgia and dates back to 2008 (nearly 20 years ago!) when the first crosses were made. Trialed extensively since 2018, it was introduced to the trade in 2024.

It’s an Ilex x crenata hybrid, which means it’s tougher than a straight Ilex crenata, said Georgia Clay, Monrovia’s plant hunter (technically plant selection specialist). Specifically, Georgia said there are regions of the country that struggle with the straight variety because of sensitivity to alkaline soil, something they likely won’t see in the hybrid. 

“So if you have issues with straight I. crenata I would still take a look at Emerald Boxer and anything in the Emerald series because Dr. Ruter has been breeding ilex for a really long time and his selections are amazing,” she added.

Emerald Boxer Holly is hardy down to USDA Zones 7 to 9, so viable in a large part of the country except those colder regions, and it can be a substitute for boxwood in those locations. And at maximum 6 ft., it’s a utility player, offering up backdrops in landscapes and even creating focal points in larger mixed containers.

It was selected because of its outstanding compact, rounded habit, something Georgia said it continued to have without trimming when she visited the trials five years after that initial selection process. Monrovia’s partnership with Dr. Ruter spans more than three decades, with Monrovia’s craftsmen selecting and trialing his seedlings—across many genera—at all three nursery locations. 

Emerald Boxer has brighter green, toothless foliage, which is a great complement to the Ruby Colonnade Holly, the first of the hybrid I. crenatas and a more upright, pyramidal form with foliage that emerges deep red and matures to green. 

The great forms and colors don’t stop there, though, according to Monrovia Plant Trials Manager Fela Lafi. 

“There’s all sorts that we’re looking at currently. Just last year we got about 300 seedlings in for trial and so we made the initial selection,” she said, adding they’re down to reviewing about 100 3-gal. containers for their potential after narrowing down the types of forms they’re looking for in future cultivars.

You can be sure, too, that those selections will have the same genetics that offer up disease and pest resistance, and mild drought tolerance in the landscape that both Emerald Boxer and Ruby Colonnade have. 

“It’s just a bulletproof plant that’s going to perform for anybody in the garden,” Georgia added. “So if we can have more shapes and sizes, it’s definitely needed.”

There’s plenty of availability for Emerald Boxer Holly, so retailers can really make a splash of it for consumers looking for intermediate-sized hedges, privacy walls and other evergreen needs. I asked Fela if there are certain component plants to pair up with Emerald Boxer and she said there’s really no plant she could think of that wouldn’t go with this versatile option. Whether it’s in sun or shade, just about any grasses, perennials, annuals or other shrubs would work with it. 

Emerald Boxer Holly ticks lots of boxes for consumers, whether they want that boxwood look without fear of disease or just a low-maintenance evergreen option. 

“We’re always looking for good boxwood replacements and this is certainly a excellent one. That was the idea to get a nice globed evergreen plant that has no insect issues, no disease issues at all,” Georgia said. “It’s just a super easy care boxwood replacement.” GP