Japanese Pagodatree or Japanese Pagoda Tree

(Fabaceae [also known as Leguminosae] - Pea Family)

Form

• large shade tree, doubling as a large ornamental tree
• maturing at about 60' tall by 80' wide, but can get even larger
• upright rounded growth habit in youth, becoming more spreading with age
• rapid growth rate in youth and middle age, becoming a medium growth rate with maturity

Culture

• full sun to partial sun
• performs best in full sun in moist, well-drained soils of average fertility, but is very urban tolerant (especially to heat, drought, pollution, compacted soils, and poor soils)
• species form is propagated by seed, and cultivars are budded onto seedling understock
• Pea Family, with several potential diseases (including branch and trunk canker [which can lead to wood rot and storm damage] and twig blight [which leads to leaf abscission and stem dieback]) and at least one potential pest (potato leaf hopper [which kills the new growth, leading to the resultant regrowth as witches' brooms])
• low availability, in ball and burlap form
• Japanese Pagodatree is somewhat sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter

Foliage

• alternate, medium to dark green, with about 9 to 13 ovate leaflets (with acute apices) per pinnately compound leaf, having faded green to chartreuse fall color
• trees will often drop a slow but continuous stream of leaflets, rachises, and entire leaves from mid-Summer through early-Autumn (before the advent of normal Autumn leaf abscission), in response to both abiotic and biotic stresses
• trees cast a light dappled shade in youth, but a much more dense shade with maturity

Flowers

• creamy-white to yellowish-green large inflorescences blanket the tree anytime from early August to early September, with about a three week bloom period
• very showy and eye-catching when in flower, since such a late-blooming performance from a shade tree is totally unexpected by passersby
• young seedling trees, especially in the northern areas of its range, may not flower for the first ten or so years of its life, but in southern areas with warm Summer nights, this liability tends to be non-existent; however, all of this is rendered irrelevant if one uses the cultivar 'Regent', which flowers at a young age

Fruits

• thick green pods mature to yellow-green fruits, with the large beans appearing as knobs within the otherwise thin pods, hanging profusely from the tree and at times weighting down the thin stems
• ripening in October and November and persisting into December or beyond, with the seeds being readily devoured by the birds, and with a resultant litter underneath the tree of the fruits or their digested residue

Twigs

• bright green in Spring on the emergent stems, becoming kelly green to medium green in Summer, and persisting as a dark green during the Winter, remaining so for several years afterwards on the young branches, slowly fading to tan on the mature branches
• very distinctive in Winter, as the twigs (in combination with the semi-persistent yellow-green peduncles and pedicels of the abscised fruits) give a unique green and chartreuse cast to the entire canopy of the tree

Trunk

• branches are lightly furrowed and chartreuse-brown, but appear as if they are subtlely striated (i.e., having light brown, diffuse, straight lines on the chartreuse bark)
• trunks have interlacing ridges and are more deeply furrowed, becoming light brown to gray-brown with maturity
• wood is relatively weak, and the branches are prone to storm damage (with or without cankers and wood rot) with their increasing age and weight
• growth habit is very rounded, resulting from the loss of the central leader at an early age (for the species form)

ID Summary

• green twigs and greenish-yellow young branches for the first four years of growth, becoming chartreuse-brown, pseudo-striated branches with age
• pinnately compound leaves that alternate along the stems, with acute leaflets
• inflorescences that flower in August or early September, maturing as pendulous bean-like fruits (with the seeds bulging beneath the pods) that abscise naturally in December or later, but are often eaten by the birds in October and November
• a chartreuse-green cast to the tree canopy in Winter, caused by the green twigs combining with the yellow-green persistent fruit stalks
• a continuous litter of leaflets, rachises, flower petals, fruit pods and beans, bird droppings, and dead stems during the entire year, especially on mature trees
• dead branches with age, often resulting from a combination of branch canker and Winter dieback

USAGE

Function

• shade, specimen, or Summer-flowering focal point tree

Texture

• medium texture in foliage and when bare
• thick density in foliage and when bare (except on young trees, which are open to average in density)

Assets

• showy creamy inflorescences in mid- to late-Summer
• rapid growth rate
• urban tolerance
• dappled shade in youth
• wildlife attraction when in fruit (especially birds; however, this can be a severe liability when sited near pedestrian or automobile traffic areas)

Liabilities

• fruit abscission (and bird deposition of fruit residue) from October through December, a true liability if the tree is sited near parking lots, sidewalks, etc.
• continuous sequence of dropping leaflets, rachises, flowers, fruits, and pedicels from July through December, and dead stem abscission year-round, all of which becomes a greater nuisance with size and age
• weak wood and brittle stems, often resulting in storm damage with age
• potential for numerous diseases and pests, including trunk/branch canker, and potato leafhopper feeding that results later in witches' brooms
• species form is slow to flower as a young tree in the northern areas of its range
• poor fall color
• marginally hardy in severe zone 5 Winters, exhibiting twig dieback

Habitat

• zones 5 to 8
• native to the Orient

SELECTIONS

Alternates

• medium- or large-sized shade trees with showy flowers in Summer (Koelreuteria paniculata, Liriodendron tulipifera, Magnolia grandiflora, etc.)
• urban-tolerant shade trees (Acer platanoides, Fraxinus pennsylvanica, Gleditsia triacanthos, Quercus rubra, Zelkova serrata, etc.)

Variants

• Sophora japonica 'Regent' - the cultivar of choice, selected for its even more rapid growth rate, relatively straight central leader, earliness to flower (at about 5 years old), and glossy dark green foliage

NOTES

Translation

• Sophora is the Arabic name for this genus.
• japonica translates as "from Japan".

Purpose

• Japanese Pagodatree is a mid- to late Summer-flowering shade tree.

Summary

• Sophora japonica is known as a large, rounded shade tree that doubles as an ornamental tree, profusely flowering in August or early September with creamy-yellow large inflorescences; however, many liabilities curtail the planting of this unusual tree in urban landscapes.