Paulownia

Paulownia tomentosa (Thunb.) Sieb. & Zucc ex Steud.

Synonyms -

Family: Scrophulariaceae

Names:

Paulownia
Tomentosa

Other Names:

Foxglove-tree because its flowers resemble Foxgloves.
Empress Tree
Karritree
Kiri (Japanese)
Princess Tree
Royal Paulownia

Summary:

A deciduous tree to 9-20 m tall x 6-10 m wide with clumsy branches forming a rounded crown with heart shaped leaves about 30 cm long and often longer on regrowth from stumps. It has upright clusters of large, fragrant, lavender flowers that produce persistent round pods.

Description:

Cotyledons:

Two. Above ground.

First leaves:

Leaves:

Opposite.
Stipules -
Petiole - Shorter than the leaf blade.
Blade - Heart shaped, usually velvety, 100-400 mm long. Green on top and paler underneath. Tip pointed. Sides convex to slightly wavy over veins to 3 lobed or toothed (especially on young trees). Base indented. Hairy especially on the underside.

Stems:

Trunk - up to 600 mm diameter x 10 metres tall. Brittle, soft wood or timber.
Branches - olive-brown to dark brown, flattened where they meet the trunk. Hairy
Twigs - light brown, stout, many pits (lenticels), circular leaf scars, bundle scars arranged in a circle. Hollow in the second year. No terminal bud, side buds are small.
Bark - greyish brown, thin, rough with shallow fissures and interlaced with shiny smooth areas.

Flower head:

Large, showy erect clusters of purple to pale violet flowers.

Flowers:

Very fragrant
Ovary -
Sepals -
Petals - Purple to pale violet, 5 lobes on a tubular base, 35-50 mm long.
Stamens -
Anthers -

Fruit:

Oval capsule, 25-35 mm long with 4 compartments with more than 2500 seeds.
Initially green and sticky, turning brown and dry with age. Stays on the tree.

Seeds:

Tiny, winged. 0.17 mg/seed.
Each tree may produce 20 million seeds.
Seeds have endosperm.

Roots:

No distinct taproot.
Shallow, horizontal and branched

Key Characters:

Persistent capsule.

Biology:

Life cycle:

Perennial. Seeds released in autumn through to early spring to be spread by wind and water. They germinate soon after contacting moist soil. The seedlings grow quickly and the tree will flower in 8-10 years. Mature trees often drop branches and rarely live more than 70 years.

Physiology:

Drought tolerant.
Tolerates coastal sea spray and wind.

Reproduction:

Flowers pollinated by insects.
By seed and suckering from roots.
Chromosome number 2n = 40.

Flowering times:

Spring.

Seed Biology and Germination:

Seed may last in the soil for at least 3 years.
Dormancy occurs in the summer after seed set.
Seeds need light to break induced dormancy. Cold storage reduces the need for light.
Needs bare, moist soil and full sunlight for good levels of germination and recruitment.
Seedlings are intolerant of shade.

Vegetative Propagules:

Readily regrows from the stump if cut down or damaged.
Adventitious buds on roots and stems allow it to survive fire, bulldozing and cutting.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Each tree may produce 20 million seeds. Seedlings colonise stream banks and rocky outcrops initially then invade surrounding areas after a disturbance such as fire, floods, disease or insect attack.
Suckers from roots can grow 4000 mm in their first season.
Seed may be dispersed up to 3.5 kilometres from the parent plant 642.

Origin and History:

China.
Introduced as an ornamental.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Full sun to partial shade.

Climate:

Winter temperatures greater than freezing.
Annual rainfall greater than 1000 mm.

Soil:

Grows on a wide range of soils including rocky slopes, infertile and acid soils.
Prefers deep well drained soils.

Plant Associations:

Significance:

Beneficial:

Ornamental, herbal medicines, timber.
Grown in plantations for export timber especially to Japan where it is used as a cabinet timber and for musical instruments.
Used for mine site rehabilitation.

Detrimental:

Weed of disturbed areas, bushland, roadsides, gardens, waterways, rocky outcrops and disturbed bushland.
Invades denuded areas. scoured riparian zones.
Dense foliage means few plants grow underneath it.
Invasive weed of the USA.
Grows rapidly.

Toxicity:

Symptoms:

Treatment:

Legislation:

Management and Control:

Remove seed trees.
Avoid disturbance in areas that have infestations close by.
Provide shade by encouraging or planting tall growing species.

Thresholds:

Eradication strategies:

Cut down the tree and paint the stump immediately with a 1:1 mixture of water and glyphosate or triclopyr. This usually stops regrowth. Small trees may be controlled by spraying the leaves with a mixture of 200 mL of glyphosate or triclopyr plus 25 mL wetting agent in 10 litres of water.
Seedlings can be manually removed providing all the root system is removed.
Larger trees can be ring barked, but regrowth from the base of the stump is common. Repeated removal of these sprouts will eventually exhaust the rot system after several years. Alternatively the regrowth can be sprayed.
Basal bark spraying of the lower 500 mm of trunk with 1 part triclopyr in 3 parts diesel is effective at any time of the year.

Herbicide resistance:

None reported.

Biological Control:

Related plants:

Plants of similar appearance:

References:

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Randall, J.M. and Marinelli, J. (1996) Invasive Plants. (Brooklyn Botanic Gardens Inc. Brooklyn). P38. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.