Winterberry (Ilex verticillata) A Favorite Native Landscape Plant

Although this winterberry (Ilex verticillata) has only a few
berries remaining, the winterberry is widely used in
wreaths and decorative holiday arrangements for its
winter color.
Photo by Brad Sylvester. Copyright 2011. Do not copy.

Driving along the back roads of New Hampshire in the fall after the leaves have dropped, it is not unusual to see the otherwise bare branches of the winterberry (Ilex verticillata) bedecked with bright red berries. In fact, you'll often see cars stopped near these wild, native shrubs clipping off the branches with the festively colored berries to weave them into homemade wreathes or to simply arrange them in vase as a holiday decoration. Winterberries are actually a species of holly plants as are all members of the Ilex genus.

I did not think that there was any winterberry growing on my property, but while taking a walk through the woods yesterday, I noticed a few dozen red berries on a thin tree-like plant that stood about 6 feet high. Winterberry! As you can see from some of the pictures on this page, it was growing in what I might call a vernal pool, if it were spring. Since it is December, however, I'll call it a wet, low-lying area flooded by recent rains and snow-melt located in the forest about twenty feet away from the edge of a stream bed.

Two small winterberry shoots can be seen to the right of
the larger main stem emerging from runner roots that
travel underground.
Photo by Brad Sylvester. Copyright 2011. Do not copy.

As you can also see from the picture on the right, the forest floor there is covered in this year's fallen leaves and pine needles. The decay of leaves and evergreen needles tends to make soil acidic, which is actually preferred by the winterberry. It also prefers very moist soil such as that found along roadside ditches, river banks, lake shores, and wet, low-lying areas in the middle of the forest.

Winterberry is shade tolerant and will grow in areas of only partial sun, such as the middle of a forest where I found this one. It will grow, much fuller and bear more fruit if it is placed in full sun since it will be able to harvest more energy from the sun which it uses to grow, flower, and fruit.

Actually, though, not all winterberry plants fruit. The plant has both male and female sexes and it is only the female plants that will produce the bright red berries. In order to do that, however, they need to be pollinated by a male winterberry plant. If you have one on your property that does not flower, then it is either a male plant, or a female plant without any male winterberry plants nearby.

Aside from the berries, which grow off the sides of young branches as shown in the pictures, the bark is a useful identification marker in the winter as well. The trunk and branches have horizontal lenticels, much like a birch tree, that break up the smooth bark. A lenticel, as we are reminded by this Cornell University publication,  is an area that allows the  plant's inner bark to "breathe," by providing permeable openings in the bark of the winterberry, which would otherwise not allow gas exchange.

In the spring, the winterberry has tiny, yellow-green flowers, which will become green berries on the female plant if pollinated. The green berries ripen around late October, turning a vibrant red. The red berries will stay on the branches through most or all of the winter, providing eye-candy for humans and a more nutritious treat for many wild animals. The USDA says as many as 48 species of birds eat the fruit of the winterberry plant as do white-tailed deer, moose, snowshoe rabbits and cottontail rabbits, as long as the latter two can reach the berries, often aided in their reach by walking atop deep snow. Winterberry plants can reach as high as 8-15 feet in height.

Propagating Winterberries

Winterberries, like many wild plants, have redundant systems of reproduction. They have fruits that contain seeds, of course, but they also send out runners, roots that travel underground and surface periodically with a new plant, like lilacs and many other shrubs. With human intervention, cuttings can be taken and rooted to make new plants as well.

Seed Propagation of the Winterberry Plant

Winterberry fruit (Ilex verticillata) and two seeds
Photo by Brad Sylvester, copyright 2011. Do not copy.

Of the three methods only the seeds produce new plants which contain a mix of the genetic material between the pollinating male plant and the fruit-producing female plant. Each berry contains 3-5 seeds each with a hard outer shell. That shell protects the seed as it travels through the digestive system of birds or other animals that eat the berries. The bright red fruit that is easy for birds to find helps ensure that the seeds are widely dispersed. Presumably, if the bird that found the berries prefers the same habitat in which it found the winterberry plant, then it will deposit the seeds, or most of them, in the plant's favored habitat although that may be far away from the parent plants.

Winterberry seeds do need to be cold-conditioned before they will germinate effectively. That means either leaving them outside and collecting them in the spring to be planted, or collecting them in the fall and winter from the ripe red berries and placing them in the refrigerator (not the freezer) for a period of 45 days or more before planting them as you would any other seed. Plants grown from seed may turn out to be either male or female plants, there's no way for the average gardener to choose, or even tell which it is until the plant is several years old and becomes sexually mature.

• Read more about cold conditioning seeds here

Winterberry Propagation by Runner Shoots and Cuttings

The runner shoots can be dug up after the leaves have dropped off the winterberry plant and it has gone dormant for the winter. The third method of propagating winterberries is to root cuttings. This is done in the spring (May-June) when the plant is primed and in growth mode. Using either of these propagation methods will result in new plants that are exact genetic copies of the plant from which they were taken. That means they will even be the same sex so plan accordingly and remember that you'll need at least one male, pollinating plant near the female plants if you want them to produce berries.

I'll write up and link some complete guides to various types of propagation, as well as handling and transplanting tips and link from each appropriate plant on this blog soon. --Follow this blog now with either Networked Blogs or Google Friend Connect (found in the margins of this page) if you don't want to miss it.--

In the spring, I'll definitely take some cuttings from this winterberry plant and add a few new plants to the more landscaped part of my yard along the stream bed in the back yard. Because winterberry is a native plant to the area and will be planted in the type of soil and conditions that it prefers. It is an eco-friendly choice for New Hampshire home-owners, requiring neither extra watering nor special pesticides or fertilizers to thrive here.