Dioecious Native for Wildlife

Learn how to get the best wildlife value from native shrubs that have male and female on separate .

article and photographs by karen Bussolini

s a lifelong gardener who grew up roaming woods and A wetlands, I’m thrilled to see peo- ple embrace native plants in an effort to cre- ate restorative, beautiful, wildlife-friendly habitats in their yards. Many natives do it all—solve problems, feed and shelter wild- life, and add beauty as well. But if you are eager to add native shrubs to your , it’s important to know a little bit about their sex lives to ensure you A honeybee visits a female Ilex verticillata for its nectar. are providing the most benefit to wildlife. A number of versatile native shrubs—includ- So why are some plants dioecious? From tors by the Xerces Society (Storey, 2011), ing willows (Salix spp.), hollies (Ilex spp.), the perspective of a , there are a lot of about 75 percent of flowering plants rely bayberries and myrtles (Morella spp.), benefits to ensuring pollen is transferred on animal pollinators, especially bees and sumacs (Rhus spp.), and spicebushes (Linde- between different plants. Among these are beetles. Plants must first attract and then ra spp.)—are dioecious, meaning they bear genetic diversity, plant vigor, viability, offer a reward—protein-rich pollen and male and female flowers on separate plants. and fruitfulness. Dioecious plants’ separa- sweet nectar—in order to perpetuate the Why is this important, you may ask? tion of sexes is a good strategy for avoiding . The incredible diversity in flower Well, the simple answer is that if you are inbreeding, but there’s a tradeoff: Male and forms, color, and scent that so engages planting dioecious shrubs, you need to female plants must bloom concurrently, in us as gardeners is the result of eons of make sure you have both male and female proximity and, except for wind-pollinated plant-pollinator co-evolution. specimens to guarantee a chance for suc- species such as bayberries, coexist with ef- Both male and female flowers of di- cessful pollination. Otherwise, it’s unlike- fective pollinators. That can be challenging oecious plants offer nectar, but only the ly these plants will develop the or for gardeners to orchestrate, but also moti- males produce nutritious pollen and only berries that add winter interest to the gar- vation to give pollinators a helping hand. females give rise to nourishing seeds and den and provide all the benefits of pollen, berries that entice and other animals nectar, and that sustain birds and POLLEN matters to distribute them. Bees, the most import-

other wildlife. According to Attracting Native Pollina- ant plant pollinators, feed on one species all photographs by karen bussolini except for this page janet davis

24 the American Gardener per foraging trip; so spicebush pollen, for instance, moves between spicebushes rather than dying on a daffodil. Bees also collect nectar and pollen to bring back to the nest for offspring. Pollen is crucial to the life cy- cle of both plants and pollinators—not to mention gardeners hoping for a beautiful display. Given this, it’s surprising that nurseries and garden centers don’t make it easier to pair up male and female dioecious plants, but other than hollies, they seldom do. Matchmaking is easier with most hol- lies, because named female cloned cultivars are typically paired with a male “consort.” Another thing to consider is that gar- deners are often advised to plant several females to just one male because the latter’s flowers are considered aesthetically insignif- icant. By skimping on males to save space for berry-producing females, however, we shortchange pollinators that need the pollen only males produce. The so-called “insignificant” flowers of the dioecious shrubs discussed in this article are signifi- cant indeed. Perhaps it’s time to adjust our aes- thetic and frame of reference. Heather McCargo, director of Maine’s nonprof- it Wild Seed Project, urges gardeners to ask, “‘How can we help other crea- tures?’—instead of it being all about us.” She encourages gardeners to grow lots of genetically diverse seed-grown male and female plants. CLUES for telling sexes apart When shopping for dioecious plants, poke around for clues. The presence of berries— often shriveled up and hard to spot—is a tipoff; lack of berries tells you nothing, as they may have been pruned, knocked off when stuffed into a hoop house to overwin- ter, eaten by birds, or plants may be imma- ture. If you do find an irresistible specimen American holly heavily laden with shiny red orbs, it’s because nurseries are swarming with pollen. It won’t look like that in your garden next year unless you give it some male company, however. Winterberry holly and northern bayberry combine with yellow twig dogwood, Virginia Ideally, try to catch plants in bloom. sweetspire, and willows to provide winter habitat for wildlife in this streamside Even then, it’s hard to tell the sex of tiny garden at Green Spring in Alexandria, Virginia. spicebush, willow, and holly flowers with the naked eye. Male and female flowers the females; their yellow pollen and glisten- have a little green bump, the ovary, in the look about the same except for anthers or ing nectar are visible under magnification. center. Bayberry males have tight conelike pistils, visible through an inexpensive 30- Male holly flowers, with four stamens in structures that expand into yellow-green 90x magnifying jeweler’s loupe. Male spice- the center, are grouped in clusters. Female clustered densely together; females bush flowers seem bigger and fluffier than flowers occur singly or in twos or threes and appear singly spread out along stems. Fer-

January / February 2018 25 Bayberry female flowers (left) are small and appear singly along stems, while larger conelike male flowers (right) are borne in dense clusters. tilized female willows develop flask-shaped McCargo urges gardeners to ask nurseries always better, for small birds can’t eat the carpals (seed capsules) filled with hundreds to start labeling male and female plants. biggest, showiest berries. For food and of tiny seeds, attached to hairs that allow That would make garden matchmaking shelter aplenty, think in terms of thickets them to become airborne. Look for bright easier for all of us. and deep garden beds instead of narrow yellow or orange coloration on otherwise foundation plantings. With thoughtful drab willow catkins. That’s the pollen, and, a versatile selection plant choices, you can surround your- as with all dioecious plants, the clear give- The native dioecious plants mentioned self with garden beauty year round and away that it’s a male. here support a diverse range of pollina- wildlife will put on its own kind of show. When I sought a female staghorn su- tors, birds, and other critters. Bigger isn’t mac for my front garden, I knew of their Willows (Salix spp.) dioecious nature and expected males Delaware-based entomologist and author along my country road to provide pol- Douglas Tallamy ranks native willows len. I got one with big fluffy panicles of second only to oaks as the best host plant for bloom—big mistake, for it was a male and moths and butterflies. Most of the 97N orth its flowers soon collapsed. The choice was American willows are small-to-medium easier later in the season, when I could de- shrubs or small with fine-textured tect immature berry clusters. Last spring foliage and low-maintenance requirements. I watched the sumacs bud and bloom. Widely distributed across the continent, As they opened, I observed male panicles black willows (S. nigra) grow the largest. becoming loose and fluffy, while female Most willows form thickets along wet edges, flowers were lumpy and held closer to the making them excellent for rain gardens, but stem. Soon the lumps turned into ber- there are also upland species like Scouler’s ries covered with red hairs; the spent male willow, also known as western pussy willow panicles drooped over, all done in. Ova- (S. scouleriana). Western prairie/riparian ries of pollinated female flowers eventually species include the golden willow (S. lutea) ripened into those energy-filled berries so and peachleaf willow (S. amygdaloides). enticing to wildlife and gardeners. Northwestern alpine willow (S. petrophila) Although local garden centers and spe- forms short, prostrate mats with large cialty mailorder nurseries are increasingly Pollen-laden anthers in this flower confirm catkins. Seek most of these species out at filling the knowledge and availability gap, that this spicebush is male. restoration nurseries.

26 the American Gardener out of hibernation. Blooming over a long thicket-forming shrub for fire-wise land- period in a season when food is scarce, wil- scaping because “its are full of mois- lows attract lots of activity. Ann DeBolt, ture.” A selection of a similar eastern species, who recently retired as staff horticulturist R. aromatica, ‘Gro-Low’ has handsome at the Idaho Botanical Garden in Boise, glossy leaves and the ability to weave its way values “every aspect of willow catkins through rocky infertile soil and always look from the fluff for nesting materials to the good, even before it erupts into blazing fall insects they draw that feed birds.” color. Although it is touted as providing ber- ries for wildlife, nobody I’ve asked has ever Sumacs (Rhus spp.) seen any fruiting, so the consensus is that it Give most sumacs plenty of room—or be is a female clone that rarely gets pollinated prepared to trim or cut them down oc- because R. aromatica males are uncommon. casionally and let them regenerate. Their Smooth sumac (R. glabra), native dense clusters of red berries (), called throughout , is an open sumac bobs, are edible and ornamental well shrub with dark green, pinnately compound into winter, and fall foliage sizzles. leaves. Shining, or winged sumac (R. copal- DeBolt favors skunkbush, also known as linum) is similar. Andrea DeLong-Amaya, lemonade bush or three- sumac (R. tri- director of horticulture at the Lady lobata), a western species. She recommends Johnson Wildflower Center in Austin, Tex- this drought-tolerant, five- to six-foot-tall, as, finds the prairie flame-leaf sumac (R. lan-

Top: Male staghorn sumacs produce small flowers in loose panicles. Above: Females are distinguished by their dense clusters of colorful, edible , known as sumac bobs.

Pussy willows (S. discolor) are common across northern North America. Julia Ku- zovkina, professor of ornamental horticul- ture at the University of Connecticut in Storrs, specializes in environmental appli- cations for willows. She notes that pussy willow catkins, protected by fuzzy gray coats, are the very first flowers in spring, providing critical nutritious pollen and Opening in early spring, pollen-laden male pussywillow flowers provide sustenance to native nectar when native bees are just coming bees and other insects during a critical period when little else is available.

January / February 2018 27 ceolata) a good choice for bank stabilization or where you have a lot of space to fill. “It’s one of the best plants for fall color,” she says, adding that it’s “pretty drought-tolerant and grows throughout most of Texas.”

Spicebush (Lindera spp.) A veil of light yellow shimmering through woods and wetlands in early spring an- nounces the presence of northern spice- bush (L. benzoin) in bloom. While the southern spicebush species (L. melissifolia and L. subcoriacea) are rare and endan- gered, northern spicebush is common from Maine to Florida and as far west as Texas. Small clusters of tiny flowers bloom on bare branches of this medium-sized single or multi-stemmed shrub. Though it blends into the greens of summer, its foliage is critical for spicebush swallowtail butterfly larvae that depend on it for food. In fall, plump, lipid-filled, red berries rip- en among butter-yellow foliage, just in time to fuel birds’ migration south. Leg- gier and less fruitful in deep shade, spice- bush is sometimes the only understory shrub that survives deer devastation.

Bayberry, Wax Myrtle A male spicebush blooms in the author’s Connecticut garden in early spring. (Morella spp., formerly Myrica) Bayberries, also known as candleberries, are Nyunt, manager of Las Pilitas Nursery in Hollies (Ilex spp.) adaptable, fast-growing shrubs with dense, Santa Margarita, California, recommends The South and Southeast are rich with aromatic foliage, an upright habit, nitro- it as a fast-growing, deer-resistant screen hollies; males in wild areas often polli- gen-fixing ability, and tolerance to coastal for coastal areas of California. “The dense nate garden females. Most hollies grow conditions and drought. shrub has a wonderful woodsy scent and as either shrubs or small trees, although Northern bayberry (M. pensylvanica) can be easily hedged,” she says. American holly (I. opaca) can reach 60 forms five- to six-foot-tall irregular semi-ev- feet in its southern range. ergreen mounds and is hardy to Zone 2. It Among evergreen species, American is a superb plant for dry, sandy, infertile, holly is the classic red-berried Christmas acidic soils, for soil stabilization, screen- holly, with two- to four-inch, dull green, ing, and hedges. The Morton Arbore- leathery leaves armed with spiny mar- tum in Chicago, Illinois has introduced ginal teeth. A pyramidal specimen matched female and male cultivars called or dense screen in the open, in the un- Silver Sprite™ (‘Morton’) and Male Silver derstory it’s charmingly irregular, often Sprite™ (‘Morton Male’) through its Chi- multi-stemmed. Slow-growing and long- cagoland Grows program. A mass planting lived, it tolerates dry or wet (not saturat- with 20 percent males should produce co- ed) soil, salt, air pollution, sun, shade, pious silvery-gray berries for the many spe- heat, and cold. With a range extending cies of birds that depend on them in winter. from coastal Massachusetts to Texas Similar in habit and value to wildlife and Missouri, it’s no wonder that holly is evergreen southern wax myrtle (M. cerif- enthusiasts have selected seedlings with era), found in pinelands and swampy areas many variations, including ‘Maryland throughout the Southeast. Andy Wasows- Dwarf’, ‘Satyr Hill’, and ‘Old Heavy Ber- ki, author of Native Texas Plants, says 40 ry’. Deer tend to avoid its prickly leaves. bird species eat the pale blue berries. Pa- American holly readily crosses with cific wax myrtle (M. californica) is more Bayberry fruits are favored by chickadees, dahoon (I. cassine), a small evergreen tree treelike, with glossy green foliage. Penny catbirds, and many other bird species. with glossy oval leaves. These naturally-

28 the American Gardener occurring hybrids are designated Ilex Resources 5attenuata and include many popular For a list of state and regional native plant societies see the AHS website: garden selections, such as ‘Savannah’, www.ahsgardening.org/gardening-resources/societies-clubs-organizations/ ‘East Palatka’, and ‘Longwood Gold’. native-plant-societies. Yaupon (I. vomitoria), a southerner Lady Bird Johnson Wildflower Center, www.wildflower.org. with a smaller-scaled presence, boasts a The New England Wildflower Society, www.newfs.org/visit. delicate filigree of branches, diminutive, North American Native Plant Society, www.nanps.org. gently-scalloped leaves, and persistent Theodore Payne Foundation, www.theodorepayne.org. red berries. DeLong-Amaya recom - Wild Seed Project, http://wildseedproject.net. mends yaupon for its disease-resistance, drought- and humidity-tolerance, and Sources low maintenance needs. “Use yaupon Great Plains Nursery, Weston, NE. https://greatplainsnursery.com. anywhere you’d use boxwood, which Overhill Gardens, Vonore, TN. www.overhillgardens.com/native-plants.html. is subject to disease and needs more Vermont Willow Nursery, Fairfield, VT. www.willowsvermont.com. water,” she says. “They’re really beau- Willamette Gardens, Corvallis, OR. www.willamettegardens.com. tiful if you limb them up and make a Woodlanders Nursery, Aiken, SC. www.woodlanders.net. multi-stemmed little tree to reveal the branching structure and silvery bark.” ‘Will Fleming’ and ‘Stoke’s Dwarf’ are upright male cultivars. Inkberry (I. glabra) is a suckering, small-leafed shrub inhabiting and wet woods from Nova Scotia to Texas. Carol Capobianco, director of the Na- tive Plant Center in Valhalla, New York, encourages use of this underappreciated beauty. “Inkberry provides structure and four-season interest in native gardens. It is also an excellent hedge or screen—use it instead of invasive border privet or the ubiquitous boxwood.” hollies are the Cinderel- las of the . Though plain green in summer, they drop their leaves in win- ter so fruits stand out dramatically. In particular, I recommend possumhaw (I. decidua), a horizontally-branched south- erner with silvery bark, and hardy north- ern winterberry (I. verticillata). “Late in winter, big waves of cedar waxwings go berserk flying from tree to tree stripping off all the berries,” says DeLong-Amaya. “It’s quite a spectacle.” A Fruitful Winter Scene To ensure a similar spectacle in my own garden, I’ve planted groupings of hollies, sumacs, and other natives that bear ber- ries less favored by birds until late winter near the windows of my home. This gives me a ringside seat for the annual feeding frenzy when migrating songbirds return, which should be any day now. m

Karen Bussolini is a long-time garden ‘Satyr Hill’ is a female selection of American holly with a dense pyramidal habit seen here photographer, a garden speaker, and an at Highstead, an arboretum and research forest in Redding, Connecticut. eco-friendly garden coach.

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