American holly

I just love the American holly that lives at our house. It constantly brings pleasure and nourishment to our lives, to the garden, and to the land around us.

This lovely tree is home to a pair of mourning doves, and bees swarm it when it flowers. (That’s also when the leaves drop, stinging my bare toes as I walk by.) When the fresh, green growth emerges, it makes a rich contrast with last year’s older, now-tired-looking leaves. The small, green fruit grows over the summer; turning deep red, it hangs on through the winter till it’s snatched by hungry birds. And during the cold, bare months when many other plants are sleeping, holly’s evergreen presence is particularly welcome.

With its strong winter-holiday connections, American holly might seem a more appropriate topic for a late November or early December column. But June is a great time to focus on holly, because you can actually plant them, watch the developing fruit, and maybe even get some answers as to why certain hollies won’t fruit — and what you can do about it.

With more than 700 species worldwide, holly is a broad and varied plant group that’s found on every continent except Antarctica. Some 150 species are in cultivation, and about 40 of those — evergreen, deciduous and hybrid — are readily available. In the Southeast, hollies are common in the landscape and are economically important to the nursery industry. Hollies in general are woody plants with smooth bark and what’s called an alternate (rather than opposite) leaf arrangement on the stem. After that, however, the similarity ends. Hollies can have spiny or smooth leaves, either evergreen or deciduous; they can be trees or shrubs, and their fruit may be red, orange, yellow, black or white. These species are equally diverse in their shape, texture and degree of adaptability.

At maturity, the American holly is a medium-sized tree (30 feet tall or more); given adequate space, it can achieve a width of 40 feet, gradually developing a beautiful, open, conical form. This North American native is found in zones 5-9, from Massachusetts to Florida, and west to Missouri and Texas. In its wild and native habitat, it’s often found in the forest understory, growing among oak, hickory, pine, sweet gum, sassafras, flowering dogwood, yellow poplar, red cedar, American beech, American sycamore and red maple.

Besides serving as a wonderful and safe nesting site for many bird species, the tree’s berries persist well into the winter and are a favorite food for many types of wildlife, such as wild turkey, northern bobwhite, mourning dove, the cedar waxwing, American goldfinch, northern cardinal, eastern gray squirrel, white-tailed deer, eastern chipmunk, meadow vole, white-footed mouse, red fox, raccoon, eastern cottontail and eastern box turtle, each of whom, I hope, will one day frequent our tree for food and shelter.

Beyond its great looks and wonderful contribution to the garden and wildlife community, American holly is present in the stories and traditions of many cultures throughout the world and has had a useful role as medicinal plant in healing traditions. And did you know that the tea yerba mate comes from a holly species of the same name native to Paraguay, Argentina and Brazil? Surprisingly, the wood of American holly is not soft and is used to create items such as handles, rulers, piano keys and violin pegs. Although considered to have a low toxicity level, the fruits are noted to be poisonous, but mostly they would only be disagreeable to your stomach if eaten in large quantities.

American holly is a slow-growing tree, but given time, love and the right conditions, it will not disappoint. It is perfect as an evergreen specimen or used in an evergreen-only or mixed hedge. The N.C. Arboretum has used them as hedging material, as individual specimens in both natural grass plantings as well as in more formal garden settings, and of course it has a very strong presence in the natural woodlands where the staff work to preserve and encourage their growth.

American holly is best transplanted as a field-grown plant and, while it can tolerate the urban landscape, it thrives on rich, moist, well-drained soils. They prefer full sun but will also grow well in part shade, as seen in the surrounding woodlands. They are not adapted to dry and windy conditions and do best if mulched and watered until established.

Unfortunately, this tree is not without problems, as it can suffer from a number of problematic but generally not debilitating pests and ailments, such as leaf miners, leaf spot, scale, to name a few. There is also the awkward winter-to-spring transition period when it drops lots of older, yellowing leaves (yes, evergreens do drop leaves), and the new young, spindly leaves come out, creating about a two-week period during which it reminds me of adolescence: long legs and pimply face. Not that I find the plant less endearing, but I was relieved when newer cultivars came on the market that make this transition more graceful. And isn’t that what we are all wanting — grace? Well, there you have it.

American holly, one of the latest evergreen hollies to flower, does so late April to early May, depending on the spring season and elevation. The flowers are quite small and not showy at all. All hollies are dioecious, which means they have male and female flowers on separate plants. So you have to have a nearby male to provide the pollen for a female to set fruit. How nearby? Some literature says a half-mile is a reasonable distance for any pollinator to journey from one holly to another, but other sources say a maximum of 100 feet will guarantee the likelihood of the bee and the pollen making its target. Since holly pollen is heavy and can’t be carried by wind, insect pollinators, such as bees, wasps and moths, are given the task of such fruitful and rewarding work.

How do you know if you have a male or female holly? Obviously, if you go out today and look at your holly and you see small, green, bead-sized fruit, she’s a female. But if you go out and don’t see any fruit you can’t be quite sure — it may be female but just was not pollinated by an eligible male in the vicinity. In this case you will have to wait for next spring, and when your holly flowers, go out and look at the flowers. You’ll be looking for a large green swelling in the center of the flower — this is the ovary, or female reproductive part. If that swelling is not there, you will most likely see very prominent stamens, which are the male parts that produce the pollen. We commonly call the fruit of a holly a berry, but if you want to be technical about it, you would call it a drupe or a multi-seeded drupe, which means that it has several stones or pits with a fleshy covering — like a peach.

Not that you may have cared about all of this, but, hey, you’ve learned something new about the birds and the bees (in the plant world) and also bagged a few more scrabble words!

In wild populations, the normal ratio of plants is seven males to one female. And if you have a wild American holly population in the woods nearby, your pollination requirements should be covered. But if they aren’t and you know you have a female, you need to bring in a male. At least one male will suffice, and it needs to bloom at the same time as the plant you want pollinated. This goes for all hollies. For American holly, it’s pretty easy because there are male and female cultivars available to choose from, assuring you good timing. You are in luck, too, because most American holly cultivars are female. So in order to get fruit, you need either a straight species male, a named male American holly cultivar or a cultivar with American holly parentage, such as the Foster Holly “Big John,” which is a cassine x opaca cross.

American holly has more than 1,000 named cultivars listed in the international checklist of cultivated Ilex, Part 1 — Ilex Opaca — obviously too many to list here. And from what I understand, area retailers don’t carry a lot of American hollies because demand is so small. So they may special order or you may have to hunt a little to get what you need.

The American holly is a tree to celebrate, to grow and to enjoy. If you haven’t had the opportunity to meet one, find one and introduce yourself. You will begin a long-lasting and fruitful relationship that will remain for all seasons — for you, for the plants, and for the animals around.

A selection of cultivars to consider

“Canary” — Yellow fruit, leaves are light green with smaller spines.

“Clarendon Spreading” — Unusual large leaf form with a low spreading habit.

“Dan Fenton” — Yes, a female, 20′ tall with lustrous dark green foliage.

“Greenleaf” — Cold-hardy attenuata form producing bright red fruit at an early age.

“Jersey Princess” female and “Jersey Knight” male — Both have glossy dark green leaves; fruit on the princess is red and plentiful.

“Merry Christmas” — Dark green foliage, fast growing with small-to-medium sized spines.

“Miss Helen” — Dark green leaves, red fruit that ripens early.

“Old Heavy Berry” — Sturdy with large dark green leaves, abundant red fruit.

“Satyr Hill” — Dense form, fast growing with large fruit, beautiful clean foliage.

“Vera” — Dense, spreading form with twisted leaves, orange-red fruit prominently displayed on top of leaves, often used as an orchard holly; for cut greenery and subsequently used for wreaths.

“f. Xanthocarpa” — Yellow-orange fruited form one of more than 50 yellow-fruited forms.

[Alison Arnold is director of horticulture at The North Carolina Arboretum. She can be reached at: aarnold@ncarboretum.org.]