Hollies are common landscape plants and even more common holiday decorations that belong to the incredibly diverse genus Ilex, which contains over 400 species, both evergreen and deciduous, that hail from all corners of the globe.
A locally adapted holly species or cultivar is relatively easy to grow, and they are fairly disease- and insect-free. They are incredibly prunable, with dormant buds ready to fill in, and many do quite well with rejuvenation near ground level if their canopy needs an overall reset.
Perhaps their biggest weakness in the landscape is alkaline soils. As with many other trees and shrubs, they tend to develop iron chlorosis in our typically more alkaline urban soils.
Evergreen species do need a bit of protection in winter, especially in exposed and windy sites in our area. Drying winter winds are stressful to all broadleaf evergreens, and many of the commonly sold hollies are only hardy to zones 4 or 5 (our area is on the border of zones 5 and 6). This overall lack of winter hardiness, along with evergreen foliage, can be a recipe for disaster if some thought is not spent on their landscape placement.
One of the most common questions in growth of landscape hollies typically lies in their berry production. Hollies are diecious, meaning that male and female flowers are born on separate plants. Therefore, a male plant is needed for pollination in order for female plants to produce berries. The typical recommendation is one male for every three to five females, although I have observed this ratio shrunk to include even fewer males.
I’m often asked how close to place male and female plants to ensure pollination, and I’ve not come across a conclusive, research-based answer. I typically plant hollies in groupings including one male and multiple females, simply because I like the look in a group.
However, I’ve often admired hollies as specimen plants in others’ landscape designs. In these instances, where individual hollies are more separated, common sense and observation has led me to believe that in most yards, situating the plants within about 100 feet of each other is sufficiently close.
However, I think this distance can likely be extended if further separation is required, since most hollies flower profusely and abundant pollinators have emerged by late spring during flowering.
When selecting holly for the landscape, I tend to lean toward natives, since that is my overall preference. Among ours, I think American holly (I. opaca) is underused and unique. It is only native to Union County in southern Illinois, but it is prolific across the South, and I’ve really enjoyed seeing it on trips. It has the quintessential evergreen leaves and bright red berries and matures into a small tree-sized plant, about 20 to 30 feet tall.
My favorite native is winterberry (I. verticillata), which is actually a deciduous species. In the absence of winter foliage, it hosts a spectacular display of bright red berries that persist for most of winter. While birds do eat the berries, they are not a preferred food source, which is one of the reasons they persist. However, this plant can be an important emergency food supply in late winter since it is one of few that holds berries.
Among non-natives, I’ve …….