More than any other native american shrubs, Ilex verticillata elicits from me a response of distilled nostalgia as well as downright bitterness. Expansive colonies of this deciduous holly existed in the swamps near my hometown in northern Michigan, and their diaphanous haze of red fruit provided a signature landscape of my youth. Stems of Christmas berry, the moniker by which I came to first know this plant, were brought inside each year for the table centerpiece. That’s the nostalgia part. I’ll get to the bitterness later.
An enormous genus of primarily evergreen species, Ilex is the only one in the family Aquifoliaceae. (Nemopanthus mucronatus, an American monotypic genus historically placed in the family, was reassigned to the Ilex following recent molecular study.) My rather reliable field identifying tool goes something like this: if a shrub or small tree possesses alternate foliage and cannot be readily assigned to any other genus, it is an Ilex. If the holly is a deciduous shrub and has two black points on the stem on either side of the leaf scar, it is I. verticillata. A closely related species from Japan, I. serrata, is somewhat more refined in appearance and has been used to create several important hybrids.
Ilex verticillata (USDA Zones 4–8) is native throughout the middle to upper northeastern corner of North America. That it is often referred to as Michigan holly—as well as Christmas berry and winterberry—adds credence to my assertion that this is the plant I savored in my younger years. It is a deciduous, multistemmed, 6- to 12-foot shrub that carries its narrow ovate, 3-inch foliage in false whorls (i.e., verticillate) around the stem. In foliage and flower, its ornamental effects are, well, quiet. It offers little in the way of autumn color, and the greenish white flowers it bears in early summer often pass without notice.
In autumn, however, any notion of a mundane existence scatters. Large, succulent red berries ripen along all the branches of the female plants. These remain until sufficient sugars develop to make them irresistible to birds.
All hollies are dioecious, meaning male and female flowers are borne on separate plants. (Dioecious literally means separate houses.) This makes good genetic sense; it ensures outbreeding in a population. However, it often leads to frustration for gardeners. Because of the wide geographic distribution of the species, blossom times of male and female garden specimens may vary dramatically. Choosing a male pollenizer that blossoms during the same week as the female is critical for fruit set.
Fortunately, horticultural selections have been made for arranged marriages in the garden. A single male plant will provide sufficient pollen for numerous females planted in the general vicinity. It should be noted that while these are good matches, if something occurs to put blossom time out of sync by as little as a week, fruiting will be sparse or absent.
Ilex verticillata is commonly found growing in perpetually wet ground; it is capable of coping with compacted, airless soils. These should be at least moderately moist and acidic. Earth abundant in organic matter will promote better growth. Alkaline soil results in yellowed foliage and stunted growth. Full sun or partial shade encourages the strongest growth and best fruiting effects.
And the bitterness part? Ilex verticillata responds to the heat and humidity offered by much of the East Coast but falters in the maritime coolness of the Pacific Northwest, where I now garden. Only during my winter visits back east can I pause to admire this particularly fine American native.