Crape myrtles (Lagerstroemia) offer the powerful triple allure of brilliant flowers (late in the season), beautiful bark, and vivid fall color. Long grown in western Oregon, they are enjoying a surge of discovery among gardeners. Often thought of as trees and shrubs for hotter climates, a wide range of cultivars have proven their adaptability in our milder summers, and others are waiting to be discovered by gardeners.
In 1974, Ted Van Veen, owner of Van Veen Rhododendron Nursery in southeastern Portland, learned of the crape myrtle breeding program at the United States National Arboretum in Washington, DC. Intrigued by the prospect of new hybrids with superior cold hardiness and greater disease resistance than the Lagerstroemia indica selections then available, Van Veen hoped to test them in Portland, at what he then perceived was their limit of cold hardiness.
In the following year, he received five new crape myrtles, unnamed and identified only by cultivar numbers, from the National Arboretum. He planted three at the front of his nursery and donated the other two to the Crystal Springs Rhododendron Garden nearby. The three trees at the nursery are still thriving and have grown into magnificent specimens, a testament to their adaptability and long-term performance in our climate.
Two of those numbered cultivars were later named (‘Muskogee’ and ‘Natchez’) and released by the National Arboretum—the first crape myrtle hybrids from their breeding program. Since that time, they have become two of the most popular and widely planted crape myrtles in the United States, and are now planted around the world. The third tree is the pure species Lagerstroemia fauriei.
According to Kathy Van Veen, current owner of the nursery, ‘Muskogee’ is the larger of the two cultivars. In thirty-five years, it has formed a broad tree, thirty feet tall, with a canopy nearly as wide. Each of its two trunks is approximately two feet around. It was this enormous crape myrtle that first caught my attention and led to my own discovery of these trees; its large and profuse trusses of lavender flowers were visible from ten blocks away.
Next to it is the slightly smaller, but equally impressive ‘Natchez’, twenty-five feet tall and as wide, with a domed canopy. The trunk and large interior branches are dramatically mottled in cinnamon red and light gray—a hallmark of this beautiful and popular tree. In early August, it is in full bloom, with pure white flowers covering the broad crown.
A Long History
Native to southeastern China, Lagerstroemia indica has been grown there as an ornamental for over 2,000 years—so long that its original natural range may only be speculative. This species of crape myrtle has a long history in this country as well. It was first noted in Charleston, South Carolina gardens in 1750. From there, its cultivation spread up to the milder parts of the East Coast, across the South to the West Coast, and into the hot-summer parts of California.
The first crape myrtles to reach western Oregon were likely brought from California in the early twentieth century. They thrive and are commonly grown in the hot interior valleys of southwestern Oregon. Though not as widely grown in the Willamette Valley, they thrive and are popular, especially when their boisterous flowers crown the trees in August and September. It is common to find clusters of them in neighborhoods where one gardener has obviously influenced another. Many old, gnarled, and picturesque specimens can be found in the oldest sections of Eugene, Portland, and Salem.
Crape Myrtle Breeding in the United States
In the mid-1960s, the National Arboretum embarked on a crape myrtle breeding program that continues today, forty-five years later. It was begun by the late Donald Egolf, a research horticulturist whose goal was to produce disease-resistant, cold-hardy crape myrtles. In the first five years, he focused on breeding and selecting pure Lagerstroemia indica for these traits. The result was the release of six cultivars in 1967 and 1970, each named for a Native American tribe, chosen to impart a distinctly American designation to introductions from this program. Several of these selections are still widely grown today, including ‘Catawba’, ‘Cherokee’, and ‘Seminole’. Though an improvement over cultivars then available, they were to be followed by a much more important milestone in breeding and development.
In 1956, a long-forgotten species of crape myrtle (Lagerstroemia fauriei) was rediscovered on the small Japanese island of Yakushima. Botanists found only one specimen on the island. Seeds collected from that tree were sent back to the United States and dispersed to arboretums and nurseries. The resulting seedling trees proved to be immune to powdery mildew, a disease that often afflicted L. indica and that the USNA breeding project had sought to eradicate. This purely white-flowered tree was less showy in bloom than L. indica, but it bore dramatic cinnamon and burgundy exfoliating bark.
Egolf began hybridizing Lagerstroemia indica with the seedlings of L. fauriei. He hoped to impart disease resistance and handsome bark to the hybrid offspring, which were assigned the name L. xfauriei. What he achieved was a lasting legacy of spectacular and popular cultivars. Disease resistance, beautiful bark, and enhanced cold hardiness were imparted to these hybrids, just as Egolf had planned. Following the release of the first hybrid selections (‘Muskogee’ and ‘Natchez’) in 1978, twenty-one hybrid cultivars would be selected, named, and introduced over the next twenty-five years. Each was thoroughly tested for disease resistance, length of bloom, and cold hardiness in Washington, DC (USDA zone 7a).
Later, a third cold-hardy species was added to the hybrid program: Lagerstroemia limii, a lavender-flowered species occasionally grown in western Oregon. Its large furry leaves and rough bark distinguished it from L. indica and L. fauriei. In 2003, the first two triple hybrids were released, fulfilling a long-sought goal: the introduction of truly red-flowered hybrid crape myrtles (‘Arapaho’ and ‘Cheyenne’) with disease resistance.
This National Arboretum breeding program continues to use names of Native American tribes, though not all of the introductions so named are hybrids; the first six cultivars were purely Lagerstroemia indica.
Crape Myrtle Performance in the Willamette Valley
The cultivars released through this program express a broad variation in habit, size, flower color, bloom time, and bark coloration. From dwarf shrubs, barely eighteen inches tall, to large and spreading shade trees, they constitute some of the most popular selections now grown in the United States. Aside from a handful of cultivars, however, they remain little known in Oregon gardens.
I was lucky to find two private gardens in the Portland area that held large collections of crape myrtles, the majority of which are National Arboretum hybrids. Both gardens had been planted in the 1980s and featured full-grown specimens of numerous cultivars. Even more fortunate, many had retained their original metal identification tags, which were still legible. Over a period of six years, I observed their growth, bloom time, bark, and fall color. I found that each cultivar exhibited a marked difference in its performance in our climate, especially in the time and length of flowering. Some consistently bloomed as early as July, whereas others bloomed late (or failed to bloom at all). Cultivars that are known for blooming at a particular season in the rest of the country did not necessarily behave that way in the Willamette Valley. There was more than just summer heat influencing this behavior. Over a period of years, I began to realize that it was irrigation and adaptability to our dry summers that were of equal importance for their best performance.
Most of the crape myrtles I observed are not readily available to gardeners, nor are there many examples of mature specimens that can be easily seen in Oregon. Others are common in the trade and becoming more common in gardens. I found that the lesser-known selections, specifically the National Arboretum introductions, were among the most impressive and successful here. Many Lagerstroemia indica cultivars fill our nurseries but offer poor to only fair performance, typically lacking resistance to powdery mildew in western Oregon gardens. Only a small selection of National Arboretum hybrids are commonly offered (‘Pecos’, ‘Zuni’, ‘Catawba’, and ‘Acoma’), but they all thrive in western Oregon.
The reason more of these hybrids are not seen is that they are seldom offered by growers who supply retail nurseries. We have begun to offer these excellent selections at Xera Plants, so they should be more readily available to Oregon gardeners; they are already gaining in popularity among garden designers. Aside from beautiful flowers at the end of summer, disease resistance, and fall color, these cultivars offer attractive bark coloration, which sets them apart from all other crape myrtles. A further attribute of crape myrtles, in general, is that their small leaves drop tidily in fall, then decompose and disappear before the gardener has time to reach for a rake.
A New Focus on Lagerstroemia indica
Another important chapter in crape myrtle breeding is the work of Dr Carl Whitcomb, of Lacebark Inc in Stillwater, Oklahoma. In the last twenty-five years, he has raised seedlings from a single vividly flowered specimen of Lagerstroemia indica, with astonishing results. Through a long and rigorous evaluation process, he has been able to select for cold hardiness and disease resistance, like those from the National Arboretum, as well as drought tolerance. His introductions, however, offer more vivid colors, including true red flowers, extended bloom time, and darkly hued foliage—a completely new look for crape myrtle.
According to Whitcomb, his new cultivars offer clearer and brighter flower colors that do not fade with age, a problem with many of the National Arboretum releases. Such vivid colors can best be imparted by pure Lagerstroemia indica. These proprietary introductions range in size from a true dwarf, Tightwad Red (‘Whit V’), to large shrubs and trees. Two of his most popular are Dynamite (‘Whit II’), with bright, true red flowers, and Red Rocket (‘Whit IV’), with enormous upright trusses of cherry red. Both are small trees to twenty feet tall. In climates with an extended hot season, they also show a rapid re-bloom. During cooler weather, the flowers may open with flecks of white, before changing to their final color. They begin blooming later in western Oregon (early September) and continue into early October.
Whitcomb’s newer introductions have pushed the crape myrtle envelope even further. Deep burgundy and wine red foliage has been combined with boldly colored flowers in three Whitcomb selections that have impressed us in our nursery. With early and profuse, shrill pink flowers, Pink Velour (‘Whit III’) offers foliage that is deep burgundy for the first month after it emerges; the leaves change slowly to deep green with maroon tints, prior to flowering. This may be one of the most cold hardy, as well. At our nursery, new growth was undamaged when a late freeze hit after our crape myrtles had broken dormancy; other cultivars were damaged, but Pink Velour was unscathed.
An upright shrub reaching ten feet in height, Burgundy Cotton (‘Whit VI’) pairs deep burgundy foliage with a long display of large trusses that open pale pink but mature to a clear sparkling white—an unforgettable combination. It is an early bloomer in our region, beginning in mid-August and continuing through September.
Possibly the most spectacular of the Whitcomb introductions is Siren Red (‘Whit VII’). Though a late bloomer in western Oregon, it has the darkest true red flowers yet. Deep glossy black flower buds open to rich oxblood red flowers in September. The foliage emerges a deep maroon and, in our climate, retains its dark coloration through the summer. A moderate growing shrub, it has reached eight feet tall and three feet wide in five years in my garden.
All three of these selections produce long-lasting displays of fall color ranging from vivid reds to oranges. Unlike the showy range of bark coloring available on the National Arboretum hybrids, these pure Lagerstroemia indica selections have a uniform but handsome smooth light tan bark. Whitcomb continues to release new cultivars, including Rhapsody in Pink (‘Whit VIII’), whose pale pink flowers are backed by deep purple foliage. We look forward to growing more of his selections and evaluating them in our climate.
Crape Myrtle Culture in Western Oregon
Crape myrtles require three conditions for peak performance in western Oregon: full sun, heat, and proper irrigation. Heat is the major catalyst that forces them to thrive and bloom well. They require a certain number of hours above 85ºF to cease vegetative growth and commence flowering. Where crape myrtle is most common (the Southeast, Deep South, and interior California), summer temperatures are consistently high, complemented by warm nights in the 60s and 70s F. These conditions bring crape myrtles into flower as early as May in the Deep South and July in the interior parts of California. The lack of heat in Oregon’s springtime is also the reason that crape myrtles leaf out late here, typically from late April to mid-May. Gardeners sometimes mistake them for dead or winter damaged. They merely need a few sunny days in the 70s.
In western Oregon, summer daytime temperatures (90°F and above) might seem to meet the requirements for heat accumulation. However, cool overnight lows (in the 50s and 60s F) mitigate those daytime highs, slowing overall heat accumulation. The heating threshold is commonly reached in mid-August for most crape myrtle cultivars. There is, however, a distinct difference in the amount of heat required for individual cultivars to initiate bloom. More than a month may separate the earliest to bloom, such as ‘Natchez’, from the last. Some may barely bloom at all here, never receiving the amount of heat they need. In earlier blooming cultivars, there may be a period of re-bloom if the weather remains hot through September. Consistently high temperatures (80s and 90s F) in early summer produce the best flowering years. Once bloom has commenced, it often continues for a month or more in the earliest selections. The age of a crape myrtle is also a factor that influences bloom time; specimens more than ten years old will usually flower earlier and more freely.
Crape myrtles should be sited in the warmest, brightest locations. They abhor shade and will grow poorly or not flower in a situation that receives less than six hours of sun. They revel in the reflected heat from pavement and walls, which makes them ideal for south-facing aspects, where other trees and shrubs become stressed. Where heat accumulation is highest, as in urban areas, crape myrtles perform at their peak, often flowering earlier than in suburban and rural locations. Planted next to a fence and near my house in Portland, a large specimen of ‘Zuni’ often begins to flower in late July; in cooler rural areas, ‘Zuni’ seldom commences bloom before late August.
Crape myrtles are often considered to be drought tolerant. They can tolerate dry conditions once established, but it is important that crape myrtles not become drought stressed. They appreciate consistent moisture as much as consistent heat to maintain steady growth from bud break to flowering. Drought-stressed plants will not bloom or will initiate bloom late. It is simple to determine when a crape myrtle requires water: well-irrigated plants have a bright glossy sheen to the leaves, whereas water-stressed trees present a dull appearance, and leaves may take on red tints long before they wilt. It is best to water them infrequently but deeply. A thick mulch around the base helps to maintain a consistent level of soil moisture. It is especially important for young plants to receive consistent moisture to develop a large root system. Under ideal conditions, they will grow surprisingly fast. I have seen specimens of ‘Natchez’ and ‘Tuscarora’, planted in loam with occasional deep soakings and mulched well, put on nearly six feet of growth in a single season.
Cold hardiness is one of the most confusing aspects of crape myrtle culture, perhaps because crape myrtles are more commonly grown in warmer southern climates. It may surprise many Westerners to learn that there is a crape myrtle walk in the Brooklyn Botanic Garden in New York (USDA zone 7a), and hardy cultivars thrive as far north as Boston (USDA zone 6a). Crape myrtles are not fussy about soil type, as long as it is well drained; rich, overly amended soil, however, can result in lush growth that may not achieve dormancy before winter, resulting in a lower resistance to cold temperatures. Young crape myrtles are more susceptible to cold damage. These two conditions combine to give them a capricious reputation for tenderness to cold. In fact, most crape myrtles are wood hardy to 0ºF, once they are established; that means that once the bark on a crape myrtle begins to exfoliate, usually three to five years after planting, the tree has reached a much higher degree of cold hardiness. Higher summer heat, which “ripens” the new growth, can also contribute to greater cold hardiness. Different cultivars also vary in their cold tolerance. The hardiest trees result from high summer heat and full sun, soils of moderate fertility, and occasional deep irrigation.
Pruning Crape Myrtles
Crape myrtles flower on wood produced in the current year, so any pruning should be done in early spring. It is best to prune as little as possible. Remove congested wood on the interior of the plant to maintain good air circulation, which helps avoid powdery mildew. Gently shape the remaining branches to enhance their natural character. As trees mature, removing the lower limbs will reveal the striking bark of the trunks. Pruning will encourage new growth but does little to enhance flowering.
Excessive pruning causes stunting and leads to unattractive scars that require time to heal; the rank growth stimulated by severe pruning may make a crape myrtle more susceptible to disease and cold damage. The most common outcome is vigorous but weak growth that is unable to support the heavy trusses of flowers; some branches may even snap at their peak of bloom. If, however, a crape myrtle has been severely pruned, it will recover quickly, and flowers are rarely sacrificed. It is this trait, combined with a powerful root system, that allows gardeners in USDA zones 5 and 6—far beyond the more common crape myrtle climates—to treat them as die-back perennials. They never achieve the beauty of exfoliating bark and tree-like stature, but they return and bloom faithfully as perennial sub-shrubs.
Crape myrtles, in all sizes, shapes, and colors, await discovery by Oregon gardeners. Though long grown here, the most beautiful and well-adapted selections have rarely been offered for sale and have stayed quietly hidden in the gardens of those willing to experiment. Thanks to the pioneering work of Ted Van Veen, the exceptional National Arboretum hybrids, offering spectacular bark, flowers, and fall color, as well as enhanced disease resistance and excellent cold hardiness, have been shown to be superior performers in our region. New selections of Lagerstroemia indica offer brighter flower colors and deep maroon or burgundy foliage. The results are in: crape myrtles are superb additions to the plant palette of western Oregon.
The Author Recommends
In my observations, the following four of the twenty-one National Arboretum hybrids stood out as exceptional. For six years, they were reliable bloomers, adapted to our dry summer conditions with little or no sign of mildew or other disease, and were not damaged in our coldest winters.
Lagerstroemia xfauriei ‘Hopi’ forms a large rounded shrub to ten feet tall. It is one of the most drought-tolerant cultivars and, as a result, is consistently the earliest to flower in our climate—often by mid-July. Flowering continues through late September, even in cooler than average summers. In autumn, it becomes a glorious vivid orange, holding its foliage for up to a month before dropping. Exfoliating bark sheds to reveal light pink and cream tones. This is an excellent cultivar that should be used in public landscapes as well as home gardens.
Lagerstroemia xfauriei ‘Osage’ has possibly the most spectacular bark of any tree in cultivation. Serpentine patches of cinnamon red are outlined in white above a layer of cinnamon red. In early August, it produces clear pink flowers in huge trusses that bend under their own weight, giving the tree a pendulous character. Autumn color is no less spectacular: deep red and orange, and long lasting. It becomes a spreading tree to eighteen feet tall. If it never flowered, it would be worth growing this charming small tree, just for its spectacular bark.
Lagerstroemia ×fauriei ‘Tuskegee’ offers spectacular flower color and an unusual wide-spreading habit, which makes it ideal as a specimen tree. To twenty feet tall and eventually as wide, it produces an abundance of intense, dark raspberry red flowers, beginning in mid-August and continuing through late September. Its bark peels to a soft sandalwood and tan, and is beautiful along the trunk and sinuous stems. Autumn color is a long-lasting combination of red and orange.
Lagerstroemia xfauriei ‘Wichita’ is a stately crape myrtle growing to over twenty-five feet. It has a vase-shaped, upright habit with a widely spreading crown. Long tapered trusses of bright lavender flowers begin to appear in early August and continue through the end of September. The exceptional bark is mottled mahogany red and orange on the trunks and branches. Autumn color is bright orange, red, and yellow. With no hint of any disease, this is a spectacular tree.
Crape Myrtles Throughout the West
Crape myrtles have long been popular in California and elsewhere in the West for their lavish summer flowers and brightly colored autumn foliage. Those most commonly grown have been selections of the common crape myrtle (Lagerstroemia indica), a species from central China that is notoriously susceptible to powdery mildew in cool, humid coastal regions. Sunset Western Garden Book recommends L. indica for zones 7-10, 12-14, and 18-21—inland, valley, and low desert regions from Southern Oregon through California to Arizona and New Mexico.
Following the introduction of Japanese crape myrtle (Lagerstroemia fauriei) in the mid-1950s, hybrid selections became available that offer greater hardiness, resistance to mildew, and striking bark coloration—in addition to all the other reasons for growing crape myrtles. While Sunset continues to recommend these hybrids for the same climate zones as L. indica, they hold great potential for use in regions closer to the coast.
. . . and in San Francisco
A single specimen of Lagerstroemia xfauriei ‘Muskogee’ rises magnificently from the editor’s garden in San Francisco, roughly five miles in from the ocean. ‘Muskogee’ has been a highlight of the garden, in all seasons, for nearly twenty-five years. The lack of heat during the summer months limits the flowering, but the brilliant autumn colors, reaching their peak at Thanksgiving, are worth the space in this small city garden.
Two healthy specimens of Lagerstroemia xfauriei ‘Natchez’ can be seen in San Francisco’s much foggier Marina District, a stone’s throw from the bay. Based upon the success of these two hybrid selections in Sunset zone 17, it makes sense to give hybrid crape myrtles a try in similar coastal regions long considered problematic for these glorious trees. RGT