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princesstree (Paulownia tomentosa)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COMMON NAMES:
princesstree
princess tree
princess-tree
paulownia
royal paulownia
empress tree
imperial-tree
kiri tree

 

SCIENTIFIC SYNONYMS:
Paulownia imperialis Siebold & Zucc.

 

CONFIRMATION STATUS: Confirmed.

 

TAXONOMY: The currently accepted scientific name for princesstree
is Paulownia tomentosa (Thunb.) Siebold & Zucc. ex Steud.

 

NATIVE STATUS: Introduced, United States.

 

GENERAL BOTANICAL DESCRIPTION: Princesstree is a deciduous
tree that may reach 69 to 105 feet (21-32 m) in height and 3.9 to 6.6 feet
(1.2-2.0 m) DBH at maturity, although it is typically smaller. At maturity,
it has thin, flaky bark. Princesstree tends to be branchy or multistemmed
when grown in the open but can have a straight bole in forests. Branches
are stout but brittle, because the pith is chambered or hollow and markedly
flattened at the nodes. Leaves of adult trees are typically 6 to 12 inches
(15-30 cm) long and 4 to 8 inches (10-20 cm) wide. However, leaves of
juvenile plants and those of stump sprouts may be much larger; for
example, juvenile leaves have been observed as long as 3 feet (0.9 m),
and leaves of stump sprouts may reach 20 to 30 inches (50-80 cm) or
more in length. Brittle branches and large leaves make princesstree prone
to wind damage and as a result, twigs, seed capsules, and other debris
frequently accumulate under the tree canopy. The inflorescence is a large,
erect terminal panicle 6 to 12 inches (15-30 cm) long with 2- to 2.5-inch
(5-6 cm) long, tubular flowers. The fruit is an oval, 2-part capsule, 1 to 2
inches (2.5- 4 cm) long and 1 inch (2.5 cm) in diameter. Each part of the
capsule has 2 compartments that contain very small (1.5-3 mm long),
winged seeds. The capsules and large, fully-developed flower buds are
conspicuous in winter. Roots can be relatively shallow to deep and well
developed, apparently depending upon soil conditions. They are typically
widely spreading without a strong taproot.

 

A clumped stand structure can result from even-aged seedling
establishment after disturbance or from expansion through root
sprouting. Establishment of princesstree in streamside forest in
Virginia associated with the large-scale disturbance of Hurricane
Camille resulted in even-aged princesstree stands 10 years after
the hurricane. Forty-three percent of recorded princesstree
populations in Austria resided within monospecific stands; this was
attributed to the species' ability to invade extremely dry sites after
disturbance.

 

Princesstree is apparently short lived. Mature princesstrees are often
structurally unsound and rarely live more than 70 years. However,
another review reports that its life span is over 125 years.

 

REGENERATION PROCESSES: Princesstree reproduces from seed
and by sprouting from adventitious buds on stems and roots. It apparently
sprouts with or without top-kill. Both methods of reproduction are
important to its reproductive success and invasiveness.

 

Flowers are pollinated by a variety of nectar- and pollen-feeding insects.

Princesstree produces many small, light seeds. Seeds weigh about 0.17 mg
each. A single seed capsule may contain as many as 2,000 seeds, so an
ndividual tree may produce 20 million or more seeds/year.

 

Princesstree reaches reproductive age early. Time to maturity depends
upon environmental conditions. It may flower in favorable environments
in its 4th or 5th year; under cultivation it may flower as early
as the 3rd year.

 

The small, light, winged seeds of princesstree are easily transported by
wind and water over considerable distances. Field observations suggest
that seedlings are occasionally located more than 2 miles (3 km) from
parent trees in mountainous regions of North Carolina and Tennessee.
This evidence one researcher to suggest that "only the largest blocks of
uninvaded forest may have areas where invasion of princesstree is
precluded by distance-induced dispersal limitations".

 

Although there is disagreement regarding the persistence of princesstree
seeds within the seed bank, it appears that princesstree develops a
transient seed bank. Seeds can survive in the soil seed bank for at least
2 to 3 years.

 

Some studies have found evidence for a persistent princesstree seed bank.
The presence of viable seeds at depths as great as 4 inches (10 cm) is a
strong indication that princesstree seeds may accumulate and remain
dormant in the seed bank for long periods of time, and that this species
might be expected to appear should the canopy open up and early
successional conditions prevail. Other studies have concluded that
princesstree formed a persistent seed bank and estimated that seeds
could survive in the soil for up to 15 years. Other studies, however, have
found no evidence of a persistent princesstree seed banks. Other research
has characterized princesstree's seed bank as large, with very high
turnover and little between-year build-up, and suggested that seed
banking was probably not important to princesstree regeneration. High
density of princesstree seeds within the seed bank may not indicate high
rates of germination and establishment after disturbance. One researcher
observed that princesstree seeds rarely, if ever, germinate in wildlands
and when they do germinate, they rarely survive more than a year. In
addition, several studies have found long-distance dispersal and prolific
seed production of princesstree apparently allows it to establish a transient
seed bank from on- and off- site sources.

 

Princesstree seed longevity appears to be relatively short. Seed
germination capacity decreases from the time of dispersal even under
optimal storage conditions in the laboratory.

 

Unlike seeds of many native trees that commonly occur with princesstree
(e.g., oak, beech (Fagus spp.), and aspen (Populus spp.), princesstree
seeds can maintain high viability despite dehydration. The seeds require
light for germination. The light requirement for germination was
considered "unusually high" when compared with other species. The
actual period of illumination required ranges from minutes to hours and
varies with seed source, year, and storage conditions.

 

Princesstree seeds are not dormant when dispersed from the mother plant.
Thus, fresh, wind-blown seeds dispersed in late summer and early fall may
germinate immediately if they reach suitable habitat.

 

According to reviews, princesstree prefers high light, exposed mineral soil,
and adequate moisture for germination and establishment; however, results
of experimental studies are variable and often difficult to reconcile given the
effect of environmental conditions on germination capacity and dormancy.
Despite their contrasts, researchers agree that leaf litter inhibits
germination of seeds and that buried seeds will likely remain dormant
until disturbance brings them up to the soil surface.

 

Princesstree seedling establishment may be infrequent and widely
scattered. Even so, princesstree has successfully expanded its range
through seeding establishment and may be more common than assumed.
For example, princesstree was characterized as the 2nd and 5th most
successful nonnative tree invading native communities in the Northeast
and Southeast as of 1986 and 2008, respectively.

 

Once established, princesstree growth may be rapid, but long-term survival
rates of seedlings is uncertain. Aboveground growth of seedlings is typically
slow during the first year, when seedlings invest heavily in belowground
growth. Rapid seedling root development makes this species difficult to
control. A shift in emphasis from belowground to aboveground biomass
accumulation occurs between the 1st and 2nd year.

 

Low survival of seedlings has been attributed to late spring frosts, drought,
disease, damaging wind, herbivory, and interference from neighboring
vegetation.

 

Light availability can impact seedling establishment, survival, and growth.
Plants in low light (intact forest) had slower growth rates, thinner leaves,
and higher specific leaf area and leaf area ratios than those in edges and
clearcuts.

 

Vegetative regeneration is important to princesstree's persistence and
spread because sprouting may allow an individual to persist after defoliation
or disturbance. Princesstree sprouts from adventitious buds on stems and
roots, apparently with or without top-kill. Sprouts generally grow faster
than seedlings; root sprouts may grow to over 15 feet (5 m) in a single
season.

 

SITE CHARACTERISTICS: Little information is available on
princesstree's natural habitat in China, largely because princesstree
has a long history of cultivation there, and much of its native range has
been altered by human activities. In China, princesstree is a minor
component of the deciduous mesophytic forest, growing chiefly in mesic
ravines, open valleys, and disturbed areas associated with species of
maple, ash (Fraxinus spp.), oak, chestnut (Castanea spp.), basswood
(Tilia spp.), and pine.

 

In the eastern United States, princesstree occurs in a variety of disturbed,
high-light environments including forest gaps and edges, streambanks and
scoured riparian areas, steep rocky slopes—particularly south slopes where
solar radiation is high—roadsides, fencerows, vacant lots, and "waste" places.
Seed germination and seedling establishment are optimum in disturbed
areas with exposed mineral soil, high light, and little to no litter; thus,
princesstree frequently establishes and spreads after disturbances that
create these conditions, such as fire, windstorms, pestilence, floods,
landslides, and anthropogenic disturbances such as construction,
cultivation, mining, and logging.

 

Princesstree tolerates a variety of soil types and conditions including low
fertility, high acidity, and drought but grows best on moist, uncompacted,
well-drained soils. In Virginia, field observations suggest that drought may
have reduced princesstree seedling survival and growth. Soil texture may
play a role in princesstree's invasiveness. In general, sandy or loamy soils
with low clay content appear optimum. Princesstree growers in the
southeastern Piedmont region of Virginia reported decreased growth and
survival on heavy clay soils; however, intense soil disturbance (i.e., soil
trenching) ameliorated the effects of heavy clays.

 

In general, survival of seedlings appears highest in disturbed soils. These
results were attributed to improved aeration of the uncompacted soils and
to reduced cover of fescue (Vulpia spp.) and other annual grasses that
resulted from the disturbance.

 

Cold climates may limit princesstree's establishment and spread. Early
and late frosts and minimum winter temperatures apparently limit
princesstree's establishment and spread in the United States. In the
United States, it is typically not invasive in regions where temperatures
drop below 32 °F (0 °C) for long periods. USDA hardiness zones 7 to 10,
where average annual minimum temperatures range from 0 to 40 °F
(-18 to 4 °C), are considered most favorable for princesstree.

 

When fully dormant, mature princesstrees can withstand temperatures
as low as -13 °F (-25 °C), but individual plants are more susceptible to
frost damage when actively growing or young and are damaged by 14 °F
(-10 °C) or lower temperatures. Damage to seeds by low temperatures
is unknown. Princesstree may be top-killed by low temperatures. Following
damage by cold, plants typically sprout. In some cases flower buds are
damaged by extreme cold. Thus, the reproductive potential of an individual
can be greatly limited in cold climates even if individual trees survive.
Predicted climate change might result in princesstree spreading beyond
its current distribution, pushing altitudinal limits upwards and latitudinal
limits northward of its current range.

 

SUCCESSIONAL STATUS: Princesstree is an early-successionalspecies

that is intolerant of shade. It possesses many characteristicsoften associated

with early-successional species and invasive behavior:1) copious production

of small, wind-dispersed seeds, 2) rapid growth ofseedlings, 3) strong shade intolerance and "poor competitive ability", 4)early age to first reproduction

(<10 years), and 5) sprouting ability.Apparently due to growth interference

by neighboring vegetation andan inability to reproduce in shade, princesstree

is a transient invaderfollowing disturbance.

 

Without repeated canopy-opening disturbance, princesstree is likely to
remain suppressed in the understory. It is rarely present in the canopy
of mature forests. Even if it persists in the tree canopy, the requirements
of high light and bare soil for seed germination may lead to reproductive
failure beneath the canopy of mature trees.

 

Without repeated canopy-opening disturbance, princesstree is likely to
remain suppressed in the understory. It is rarely present in the canopy of
mature forests. Even if it persists in the tree canopy, the requirements of
high light and bare soil for seed germination may lead to reproductive
failure beneath the canopy of mature trees.

 

The frequency and scale of disturbance may be important to establish-

ment and persistence of princesstree. Several reviews note that princess-

tree invasion of native forests may be primarily facilitated by large-scale
disturbances, which are more likely to result in reduced interference from
other vegetation, high light, and exposed mineral soil necessary for optimal
establishment. Establishment of princesstree in a streamside forest after
Hurricane Camille peaked immediately following the hurricane and

decreased over time. Sixteen years after the disturbance, no new individuals

were recruited. The author attributed this to a lack of disturbance since the

hurricane and overshading by native vegetation.

 

SEASONAL DEVELOPMENT: Princesstree pollen is fully developed
before winter and pollination occurs in spring. Flowers bloom before the
leaves begin to emerge in late April or early May. Leaf expansion begins
about 2 weeks after flowering. Flower buds begin to appear in the leaf
axils in late July or early August. They develop through summer, mature
in October, and are visible as terminal panicles after leaves fall in autumn.
Leaves are retained in autumn until after the first frost. Seeds mature in
September, and capsules ripen and open in October. The capsules may
remain on the tree for long periods. The capsules break open and seeds
are disseminated by wind throughout winter and into spring.

 

GENERAL DISTRIBUTION: Princesstree is native to eastern and
central China, where it occurs south of the 32 °F (0 °C) isotherm. With the
exception of Antarctica, princesstree has been cultivated in every continent
of the world. It was most frequently introduced as a crop tree but also as
an ornamental. Princesstree appears to be less invasive in Europe than in
North America. However, it has received attention in Europe due to
increases in the number of localities where it has been observed since
the 1980s. In Australia, princesstree is considered potentially invasive;
invasiveness in other foreign countries had not been reported as of 2009.

Princesstree is nonnative in North America. It occurs from Montreal,
Canada, south to Florida and west to Texas and Indiana; it has also been
planted in coastal Washington and California. Princesstree has escaped
from cultivation and spread extensively to portions of the southeastern
and middle Atlantic states. It is invasive from Pennsylvania south to
Georgia and west to Missouri.

 

SKY MEADOWS DISTRIBUTION:

 

Tree specimens can be found on trails marked in red.

 

       Bleak House
       Appalachian Trail/Old Trail
       South Ridge/North Ridge
      
Gap Run
       Snowden
       Woodpecker Lane

       Sherman's Mill
       Rolling Meadows/ Lost Mountain
       Fish Pond

 

The specific distribution of princesstree has not been determined. One

conspicious specimen can be seen from Gap Run Trail.

 

HABITAT TYPES AND PLANT COMMUNITIES: Plant community
associations of nonnative species are often difficult to describe accurately
because detailed survey information is lacking, there are gaps in
understandings of nonnative species' ecological characteristics, and
nonnative species may still be expanding their North American range.

Princesstree occurs in a variety of habitats and plant associations
throughout the eastern United States that are similar to those of its native
range . It may be a minor, occasional, or important component of plant
communities of which it is a part. For example, in debris avalanches
following Hurricane Camille in central Virginia, princesstree established
at densities ranging from 75 to 310 stems/ha on 3 of 4 study sites
dominated by yellow-poplar (Liriodendron tulipifera), sweet birch
(Betula lenta), black locust (Robinia pseudoacacia), and red maple
(Acer rubrum), thus becoming an important component in the forst.
However, in a streamside forest in central Virginia, it had the lowest
importance value among the 4 dominant forest trees of the study
area (yellow-poplar, sweet birch, and sycamore (Platanus occidentalis)).

In other parts of the eastern United States, princesstree occurs in
disturbed upland areas associated with early-successional species such
as maple (Acer spp.), oak (Quercus spp.), and pine (Pinus spp.).

 

Common associates on disturbed sites in Blue River Gorge in the Blue Ridge
Mountains of Virginia include Virginia pine (Pinus virginiana), red maple,
American elm (Ulmus americana), blackjack oak (Quercus marilandica),
eastern redbud (Cercis canadensis), sassafras (Sassafras albidum), sweet
birch, and smooth sumac (Rhus glabra). Princesstree was described as an
"aggressive" invasive species within disturbed areas at the Oak Ridge
National Environmental Research Park in Tennessee; at this site, adjacent
uplands were characterized by 2nd- and 3rd-growth oak-hickory-maple
forests. In the Great Smoky Mountains National Park, Tennessee,
princesstree occurred by streams with yellow-poplar, sweet birch, and
sycamore. In eastern Pennsylvania, princesstree was a minor
component in a 5-acre (2 ha) mixed-hardwood forest gap. Allegheny
blackberry (Rubus allegheniensis) and American pokeweed (Phytolacca
americana) dominated the vegetation of the tornado-formed gap. Along
the Green River Gorge, North Carolina, princesstree was locally abundant
within disturbed cove hardwood forest dominated primarily by yellow-
poplar and basswood (Tilia americana). In Great Falls Park in Fairfax
County, Virginia, it occurred in American beech-white oak-red oak-yellow-
poplar forest with American holly (Ilex opaca) and Christmas fern
(Polystichum acrostichoides) in the understory.

 

IMPORTANCE AND USES: Native to China princess tree is a fast-grow-

ing, deciduous tree that is primarily grown for its profuse spring bloom of

foxglove-like flowers and its large catalpa-like green leaves. It was first

introduced into the United States in the mid 1800s, and has since escaped

cultivation and naturalized in many areas of the eastern U.S.

 

Although used in Japan for lumber, princesstree has little commercial

value due to limited economically viable timber stands.

 

 

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