ailanthus/tree-of-heaven (Ailanthus altissima)
tree of heaven
Ailanthus altissima forma erythrocarpa (Carr.) Schneider
CONFIRMATION STATUS: Confirmed.
TAXONOMY: The scientific name of tree-of-heaven is Ailanthus
altissima (Mill.) Swingle. It is in the Quassia family (Simaroubaceae),
a family of mostly tropical woody plants.
NATIVE STATUS: Introduced, United States and Canada.
GENERAL BOTANICAL DESCRIPTION: Tree-of-heaven is a
nonnative, deciduous tree. It may reach 60 to 70 feet (18-21 m) in height,
80 feet (24 m) in crown width, and 3 feet (0.9 m) in trunk diameter at
maturity. The champion tree is in Tennessee, and reaches 67 feet (20 m)
in height, 64 feet (19 m) in spread, and 20.6 feet (6.3 m) in diameter. Trees
may be shrubby when suppressed or regularly pruned. Tree-of-heaven has
smooth, thin bark and a straight bole. Branches are brittle and self-pruning.
The large, malodorous leaves are pinnately compound, with prominent
glands on the back of each leaflet. Surface-to-volume ratio of leaves is high:
leaflets range from 15 to 41 in number, and total leaf length may reach 3
feet (1 m). Leaf stipules have nectaries that excrete sugars.
Most flowers are unisexual, but some trees may have perfect flowers. The
inflorescence is a 0.3- to 0.6-foot (10-20 cm) panicle with 6- to 8-mm-long
flowers. Staminate flowers have a strong, objectionable odor. Fruits grow in
clusters of 1-seeded, dry schizocarps with wings. They are 2.5 to 5 cm in
length and propeller-shaped, resembling maple (Acer spp.) fruits. A fruit
cluster contains hundreds of seeds that average 0.6 × 0.25 cm in size and
27 mg in mass.
Roots are shallow, widely spreading, and capable of sprouting. Young trees
have a taproot and several large laterals, although the taproot may diminish
with tree age. In dry, rocky soil or beneath pavement, trees grow long
horizontal roots that do not branch until more favorable soil is found. Roots
near the trunk thicken with age, serving as storage organs. Most roots
occur in the upper 18 inches (46 cm) of soil. Deep roots send out smaller
roots that grow near the soil surface; adventitious shoots generally arise
from these shallow roots.
Tree-of-heaven typically occurs in clumps, although it may form rows along
streams, roads, and fences and occasionally grows as widely spaced, single
stems. Clumping can result from an even-aged seedling establishment or
from colonial expansion through root sprouting . Open-grown colonies may
eventually become dense by sprouting. Stands subject to infrequent
control measures may develop into even-aged thickets. Untreated stands
self-thin, eventually forming uneven-aged sprouts. Sprouts volunteering
in closed-canopy understories remain suppressed and few in number.
Investigations of tree-of-heaven in China give little clue as to the species'
natural growth habit. Tree-of-heaven grows in a densely populated area
of China where no wildlands are left. As valued ornamentals, mature trees-
of-heaven in China are pruned to aesthetically pleasing, single-stemmed
forms. Sprouts are harvested for firewood and medicinal uses.
Tree-of-heaven is typically short lived, with an average life span of 30 to
50 years. Cloning from root sprouts can extend ramet life hundreds of
years. Sprouts from the 1st tree-of-heaven in North America, planted in
Philadelphia's Bartram Botanical Garden 1784, still exist today. Tree-of-
heaven appears to be allelopathic. Chemical extracts from the leaves,
barks, roots, and seeds have inhibited germination and growth of other
species in the laboratory. Allelopathic chemicals (ailanthone and other
compounds identified in are most concentrated in roots, with young
ramets producing more toxins than older trees. Reciprocal transplant
experiments may help determine the degree of tree-of-heaven
allelopathy under natural conditions.
Open-grown trees-of-heaven are highly efficient at photosynthesis, and
store large quantities of photosynthate in stems and roots. Foliar nectaries
appear to maintain carbohydrate balance during growth and flower
initiation by excreting photosynthates.
Tree-of-heaven is sensitive to ozone pollution; however, it is highly tolerant
of most industrial pollutants. In a highly polluted area of Armenia, tree-of-
heaven showed the least damage and best growth of 8 urban tree species.
REGENERATION PROCESSES: Tree-of-heaven reproduces from seed
and root sprouts. Both methods are important to tree-of-heaven's invasive-
ness and reproductive success.
Tree-of-heaven is mostly dioecious. Rarely, either bisexual trees or trees
with both bisexual and unisexual flowers are found.
As with most species with wind-dispersed seed, tree-of-heaven appears
to have a relatively uniform genetic system, with most diversity occurring
among rather than within populations. Because North American tree-of-
heaven populations originated from only 3 introductions, they may be even
less genetically diverse than native Asian populations. A comparison of
seedlings germinated from seed collections from 5 locations across the
United States and 5 locations across China showed significant differences
in height growth, root:shoot ratios, and leaf area among United States and
Chinese seedlings. Populations from the United States were taller, allocated
relatively less biomass to roots than stems, and had greater leaf areas,
compared to Chinese populations. There are also significant differences
between North American and Chinese tree-of-heaven for seed and seedling
Tree-of-heaven is pollinated by a variety of nectar- and pollen-feeding
insects. Although disagreeable to humans, the strong odor of male flowers
attracts honey bees, beetles, and other insects.
Tree-of-heaven produces many small, light seeds.Flower, fruit, and seed
production begin early. Six-week-old seedlings have flowered, and 1-year-
old saplings and 2-year-old root sprouts have been observed with fruit.
Best seed production is from 12 to 20 years of age. Mature female trees
may produce several hundred inflorescences in a year. An individual flower
contains hundreds of seeds, so individual trees can produce 325,000 or
more seeds per year. Estimates for one small, 12-inch-diameter (30-cm)
tree in Pennsylvania was for a production of over a million seeds. Most
seed are viable, even those that overwinter on the tree and disperse in
The winged fruits are easily and widely dispersed by wind. Water and
machinery also disperse seeds. Distance traveled for seed dispersion is
significantly greater compared to many other wind-dispersed species.
Seeds retain dormancy for less than a year, so seeds do not build up
long-term seed banks in the soil.
Seed can germinate in highly compacted soil, and is salt tolerant. Studies
of eastern hardwood species found roadside salt does not appreciably
affect tree-of-heaven germination; native oak and birch seed is far more
adversely affected by salt. The tree-of-heaven embryo is well equipped
for rapid growth. Although it lacks an endosperm, it has 2 large cotyledons
with stored oils. Litter has both negative and positive effects on germ-
ination. In eastern deciduous forests, oak (Quercus spp.) leaf litter has
been shown to delay tree-of-heaven germination and increase mortality,
but not affect subsequent biomass of surviving seedlings.
Litter may have positive effects on tree-of-heaven germination and
establishment by reducing competition from herbaceous species.
Although seed production is prolific, tree-of-heaven seedling establish-
ment is infrequent on many sites. Dry climate may limit tree-of-heaven
recruitment in the Great Plains and the arid West. Even so, tree-of-heaven
has successfully expanded its range through seed spread, and seedling
establishment appears to be more common than commonly assumed.
Whether initial regeneration is accomplished from seed or by cloning,
once established, tree-of-heaven growth is extremely rapid. It may be
the fastest-growing tree in North America. Both the species' common
and scientific (Ailanthus, sky-tree) names refer to its ability to attain
height quickly. Seedlings attain 3.3 to 6.6 feet (1-2 m) in their 1st year.
Saplings average an additional meter of height growth per year for at
least 4 years. Relatively rapid growth continues for larger trees: In a
New England survey, tree-of-heaven reached 33 to 49 feet (10-15 m)
in height and 3.7 to 4.3 inches (9-11 cm) dbh in 30 years. Growth is
fastest in California trees, which are typically 35 to 63 feet (10-20 m)
high by 12 to 20 years of age. Growth slows greatly after age 20 to 25,
with height increases of 3 inches (7.6 cm) or less per year. Once
established, tree-of-heaven density increases by root sprouting.
Cattle, deer, and small rodent browsing may retard tree-of-heaven
establishment and growth. Browsing effects probably vary by site and
Tree-of-heaven sprouts from the roots, root crown, and bole. Although
tree-of-heaven reproduces well from seed, sprouting is the more common
method of regeneration. Young trees, cut to the root crown before bark
becomes thick and corky, often sprout from both the root crown and roots.
Bole damage promotes root, root crown, and bole sprouting. Death or
injury of the main stem usually results in prolific root sprouting. Even as
seedlings, trees-of-heaven produce horizontal roots capable of sprouting.
Root sprouting is an uncommon regeneration strategy for woody species,
but it is a powerful strategy for species employing it. Roots have more
nutrient- and photosynthate-storing capacity than rhizomes, conferring
better protection from aboveground disturbances such as fire.
With tree-of-heaven's spreading root system, root sprouts may appear
as far as 50 to 90 feet (15-27 m) from the parent stem. Sprouts of all
types (root, root crown, or bole) generally grow faster than seedlings.
In the East, average rate of growth is reported as 6 feet (1.8 m) per year
for bole sprouts, 2.7 feet (0.8 m) for root sprouts, and 1.3 feet (6.5 m)
for seedlings. Root sprouts in California may exceed 3.5 feet (1 m) in
their 1st year.
During drought, tree-of-heaven pulls stem water into roots and begins
stem die-back. Stem die-back may be extensive during extended droughts,
but tree-of-heaven typically survives drought by sprouting from the roots
when there is sufficient water to support new growth. Frost die-back and
regrowth is common in tree-of-heaven's northern limits.
SITE CHARACTERISTICS: Little information is available on tree-of-
heaven's natural habitat in China, but tree-of-heaven has a wide ecological
amplitude in North America. Human settlements are most likely centers of
distribution for tree-of-heaven, with roads providing the migration routes.
Tree-of-heaven occupies a wide range of conditions, from very poor to very
productive sites. tree-of-heaven is significantly correlatedwith urban areas
where rooting space was limited and other species could not establish. In
Central Valley of California, tree-of-heaven has an 8-month growing season
and grows in soils that are among the most nutrient-rich and productive in
Tree-of-heaven has been termed "the most adaptable and pollution tolerant
tree available". Highly tolerant of industrial gases, dust, and smoke, tree-of-
heaven is common on disturbed sites, especially alleyways, roadsides, and
fence rows. In wildlands, tree-of-heaven occurs on disturbed sites, open
woodlands, and riparian zones. In the Southwest, tree-of-heaven invades
canyons, arroyos, and riparian zones including the banks of the Rio Grande.
After Hurricane Camille, it was associated with debris avalanche chutes in
Tree-of-heaven tolerates a wide range of soil conditions. For example, in
oak-hickory woodland of Sussex County, New Jersey, tree-of-heaven
occurs in permanently swampy, ridgebottom soils of an abandoned Boy
Scout camp. At the other moisture extreme, large, water-storing roots
enable tree-of-heaven to tolerate dry, rocky soils and extended drought.
Even seedlings show drought tolerance, often volunteering in pavement
cracks and other dry sites.
Tree-of-heaven also tolerates a range of nutrient conditions. Best growth
occurs on nutrient-rich, loamy soils but tree-of-heaven tolerates nutrient-
poor soils. In reclamation studies, tree-of-heaven tolerated acid mine spoils.
It tolerates compacted soils.
Tree-of-heaven's spreading root system permits establishment and growth
on cliff faces and other steep inclines.
Tree-of-heaven is the only species in its genus that tolerates cold climates.
Climate within tree-of-heaven's North American distribution varies widely,
from subtropical and wet in Florida, arid in the Great Plains and Great
Basin, to cold and wet in the Northeast. Tree-of-heaven tolerates as little as
14 inches (360 mm) of annual precipitation under 8 months of drought in
the arid West, and as much as 90 inches (2,290 mm) annual precipitation in
the Appalachian Mountains. Annual mean maximum and minimum
temperatures are 15 and 97 oF (-9 and 36 oC). Large, water-storing roots
confer drought tolerance. Extreme cold and prolonged snow cover restrict
its occurrence to lower slopes in mountainous regions, as seedlings are not
cold resistant. Tree-of-heaven may be able to colonize cold regions that
experience several successive years of mild climate.
SUCCESSIONAL STATUS: Tree-of-heaven is an early successional
species. Starting with a few stems along roadside or woodland edges, tree-
of-heaven may encroach into meadows, woodlands, and open forests. It
commonly invades open eastern hardwood forests, eventually sharing the
canopy with native hardwoods . Tree-of-heaven and princess tree
(Paulownia tomentosa) are the 2 most successful nonnative trees invading
hardwood forests in the Northeast, where they often establish after tree
harvest or other disturbance.
Tree-of-heaven rarely occurs in closed-canopy, late-successional hardwood
forests, but can establish in closed-canopy and old-growth forest canopy
gaps such as those created by woolly adelgid or gypsy moth defoliation,
windstorms, or possibly fire. For example, tree-of-heaven occurred in 2 of
4 avalanche debris chutes surveyed 10 years after Hurricane Camille, but
did not occur in adjacent, undisturbed hardwood forest in Nelson County,
Virginia. Its growth rate is such that tree-of-heaven can reach the
surrounding canopy rapidly, without further need of disturbance. Besides
its genetic capacity for growth, its relative unpalatability compared to
associated hardwood species may confer further growth and successional
advantage to tree-of-heaven in eastern hardwood forests with dense white
-tailed deer populations. Once established, tree-of-heaven can spread into
the surrounding understory by root sprouts, which grow slowly but persist
under low light conditions.
Tree-of-heaven is intolerant of deep shade; it does not photosynthesize
efficiently in shade. Mortality rate was over 90% for experimentally
planted tree-of-heaven seed planted under a closed-canopy oak-hickory
forest. Similarly, mortality of naturally established tree-of- heaven seedlings
under an oak (Quercus spp.)-maple sugar canopy in West Virginia was
100%. Although tree-of-heaven cannot successfully regenerate from seed
under its own canopy, it does produce under-canopy sprouts. Without
canopy-opening disturbance, under-canopy sprouts remain suppressed
and grow slowly.
Tree-of-heaven's reputed allelopathy may slow succession in plant
communities where it is invasive. Concentration of allelopathic chemicals
is highest in young tree-of-heaven stands. Seasonally, toxins are greatest
in spring and decline as the growing season progresses. Allelopathic
chemicals are present in all portions of the tree, but are most concentrated
in roots. The litter is also allelopathic.
SEASONAL DEVELOPMENT: Leaf expansion begins in early spring,
and flowering and pollination follow in late spring. Seed ripening begins in
late summer and continues through fall. Fruits usually persist on female
trees through winter, but may disperse anytime from October through the
next spring. Entire seed clusters may break off and disperse as a unit.
GENERAL DISTRIBUTION: Tree-of-heaven is native to Taiwan
and central China, where it occurs from 22 to 34o North in latitude. In
North America it occurs from British Columbia, southern Ontario, and
Massachusetts south to Florida, Texas, and southern California. Tree-
of- heaven spread in North America apparently followed 3 distinct
introductions from China. It was 1st imported to Pennsylvania in 1784
as an ornamental. Another introduction occurred in New York in 1820,
where tree-of-heaven was again planted as an ornamental. Both eastern
introductions were from English stock imported from China. Tree-of-
heaven was commercially available in eastern nurseries by 1840, and is
now widespread in the Northeast. The 3rd introduction was in California
during the mid-1800s gold rush. Chinese immigrating to work in the gold
fields and in construction of the transcontinental railroad brought tree-of-
heaven to California, probably because of the tree's medicinal and cultural
importance in their homeland.
A century after the North American introductions, tree-of-heaven is most
common in its initial centers of distribution: the Northeast and California.
In the East, it is invasive from New England south to the mid-Atlantic
states. Tree-of-heaven is frequently found in the Midwest, becoming
uncommon in the Great Plains and the South. It is weakly invasive in the
Great Plains and is rare south of North Carolina in the Southeast and South.
In the West, tree-of-heaven is common in California and locally frequent in
Oregon and Washington. In California tree-of-heaven occurs in the Bay
Area, the Central Valley, and in foothill counties with a history of gold
mining. In the Pacific Northwest it grows along waterways, including
banks of the Snake and Columbia rivers. In the Southwest it occurs
in riparian zones and mesic canyons.
Tree-of-heaven has established in temperate climates throughout the
world. Its earliest introductions may have been in Japan and Korea,
where it is probably not native. It was introduced in Europe in the 1700s
and became widespread there. Introductions in Argentina, Australia,
and Africa followed, using seed from European trees.
SKY MEADOWS DISTRIBUTION:
Tree specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
The specific distribution of tree-of-Heaven has not been determined.
HABITAT TYPES AND PLANT COMMUNITIES: Tree-of-heaven is
most common in urban areas. It may be an important, occasional, to minor
component of wildland vegetation anywhere within its North American
range. In wildlands of the East and Midwest, tree-of-heaven is a common
component in oak-hickory (Quercus-Carya spp.) and maple-birch-beech
(Acer-Betula-Fagus spp.) forest canopies. For example, tree-of-heaven
has infested hundreds of acres of oak-hickory forest in Shenandoah
National Park, Virginia. Tree-of-heaven is frequently associated with
black locust (Robinia pseudoacacia), a native early successional species,
and nonnative Norway maple (Acer platanoides), in eastern oak-hickory
forests. Other early seral associates are black cherry (Prunus serotina),
gray birch (Betula populifolia), sweetgum (Liquidambar styraciflua), and
eastern redcedar (Juniperus virginiana). Weedy invaders other than tree-
of-heaven include Japanese barberry (Berberis thunbergii) and multiflora
rose (Rosa multiflora). Late-successional understory species include white
ash (Fraxinus americana), black cherry, sassafras (Sassafras albidum),
and boxelder (Acer negundo).
IMPORTANCE AND USES: There are few reports of either wildlife or
domestic animal use of tree-of-heaven. A few birds such as pine grosbeak
and crossbills eat the seeds. White-tailed deer and domestic goats browse
the foliage. Since free-choice trials or other palatability studies have not
been conducted for white-tailed deer and domestic goats, it is difficult to
assess relative preference for tree- of-heaven for either browser.
Although browsed, tree-of-heaven is not reported as preferred browse for
ungulate species. The bark and leaves contain saponins, quassinoids, and
other bitter compounds that may discourage consumption. Small animal use
of tree-of-heaven is largely unknown. One old-field study in New York
showed white-footed mice preferred browsing eastern white pine, sugar
maple, and white ash over tree-of-heaven. The same study noted meadow
voles preferred tree-of-heaven seedlings over eastern white pine seedlings.
Further research is needed on animal use of tree-of-heaven.
Tree-of-heaven wood resembles ash (Fraxinus spp.) wood in appearance
and quality. It is easily worked with tools and glue, and takes a finish well.
Tree-of-heaven is an important timber and fuelwood tree in China, and is
planted for timber and afforestation in New Zealand, the Middle East,
eastern Europe, and South America.
In China, tree-of-heaven is grown commercially as a host for Attacus
cynthia, a silkworm that produces coarse, durable silk. Tree-of-heaven
is a food for honey bees worldwide. Initially bad-tasting, tree-of-heaven
honey ages to a high-quality, flavorful product.
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