Tuesday, May 25, 2010

Koelreuteria - Golden Rain Tree

A small genus ( tribe ) of trees in the Sapindacacae family that includes 3 species of trees. They prefer full sun to partial shade and deep, fertile, well drained soil as well as hot summers. Keep in mind when fertilizing; they love potassium.
The Koelreuterias are tolerant of drought, heat, salt and urban conditions. Propagation from root cuttings taken in late winter is best since seed grown trees are variable in habit. The seed germinate best if kept in the refridgerator over the winter and planted out in the spring. They can be weak wooded but unlike Bradford Pears; this tends to only happen on trees not properly trained when young.
Young trees are best pruned to a single leader, feathered and thinned.
They are best planted in the lawn where the seedlings do not cause trouble.

* photo of unknown internet source


Koelreuteria bipinnata ( Chinese Flame Tree )
The Chinese Flame Tree is a native to Yunnan Province in sw. China. This tree is rapid growing, has beige bark and grows with a spreading crown to 82 x 60 feet with a trunk diameter up to 2.5 feet. No trees close to this size have ever been reported in England; this tree clearly prefers the hot humid summers of the eastern U.S., eastern Asia and places in southeast Europe such as Romania. Much slower growing in England; 23 feet would be about the maximum size there.
Otherwise fast growing; it can reach up to 30 feet in 10 years where summers are hot.
The bipinnate leaves, up to 2 feet in length, are composed of finely-toothed, oblong leaflets up to 5.5 x 2.5 inches in size. The foliage is luxuriant mid green, turning to deep golden-yellow late in the fall.
The yellow flowers are born in large panicles ( up to 30 x 18 inches ) in late summer and are followed by the red elliptic bladder like seed pods in tall clusters.
It is hardy from zones 6 to 9 ( -7 F with no injury, possibly colder ) and is drought, heat, salt and urban tolerant. It prefers rich, well drained soil in full sun. Easy to propagate, the seed germinates easily with scarification and cold stratification.


* photos taken on May 8 2010 @ U.S. National Arboretum, D.C.




* photos taken on 4th of July @ U.S. National Arboretum, D.C.



* photo taken on July 17 2010 @ Morris Arboretum, Philly, PA

* photo taken on October 17 2010 @ U.S. National Arboretum, D.C.

* photo taken on Sep 3 2017 @ U.S. National Arboretum, D.C.


var 'integrifolia'
Also called Koelreuteria integrifolia. Similar but larger and even more vigorous. Some records include: fastest recorded growth rate - 10 feet x 2 inches; 4 years - 28 feet with a trunk diameter of 14 inches! It is a great tree for parks and highways but not near sidewalks.

Koelreuteria elegans ( Flamegold Tree )
A flat topped medium sized tree native to Taiwan that typically reaches around 50 feet. On ideal sites, some records include: 3 years - 13 x 4 feet; largest on record - 80 x 80 feet with a trunk diameter up to 2.5 feet.
The bipinnate leaves are up to 30 inches in length, narrow and fernlike. The leaves include up to 16 leaflets that are medium green and up to 5 x 1.5 inches in size.
It is evergreen in the far south of the U.S.
The yellow flowers are borne in large panicles from late summer into autumn and are followed by rosey-red fruits that split into 3 ovoid segments when ripened remaining on the tree and turning brown by winter.
Hardy zone 8 to 12. Naturalized in Florida.

* photo taken on Jan 3 2011 @ Deerfield Beach Arboretum, Florida


Koelreuteria paniculata ( Golden Rain Tree )
A Chinese, Korean native that is naturalized in Japan and parts of the U.S. & eastern Europe. This is a very attractive, broadly-spreading tree that blooms during late summer after most trees are long finished. It is fast growing to 40 feet or more on good sites. Some records include: fastest recorded growth rate - 5 feet; 5 years - 20 x 7 feet ( 13 feet is more normal ); 10 years - 30 x 30 feet; 20 years - 50 x 40 feet; largest on record - 90 x 60 feet with a trunk diameter of 4 feet. No trees close to this size have ever been reported in England; this tree clearly prefers the hot humid summers of the eastern U.S., eastern Asia and places in southeast Europe such as Romania. Much slower growing in England; 45 feet would be about the maximum size there. Often gaunt and sparse in habit when very young; the Golden Rain Tree later develops a full and dense canopy. Moderately long-lived, the Golden Rain Tree can persist for as long as 250 years.
The foliage up to 16 inches ( to 30 inches on very vigorous shoots ) in length, is pinnate to bipinnate on vigorous shoots and is large. The 11 to 17 oblong to elliptical leaflets ( up to 6 x 3 inches in size ) are coarsely toothed or scallop lobed. The foliage is reddish when young, maturing to deep green then turning golden yellow to orange ( rarely scarlet ) during autumn. The leaves appear early in spring.
The yellow flowers, up to 0.5 inches, are borne in large conical panicles up to 24 inches in length at the ends of the shoots during mid summer.
They are followed by attractive rosy red fruits up to 2 inches in length in the fall that ripen to pale brown.
The shallowly-fissured bark is pale brown.
The twigs are crooked, stout and grayish.
Hardy zones 4 to 9. Very heat, drought, alkaline, wind and moderately salt tolerant though does not like to be transplanted at large sizes or in the fall. Can be prone to Coral Spot fungus. Propagation is very easy from seed if it is soaked in sulfuric acid for 60 minutes before sowing. An excellent urban street tree

* photo taken in Niagara Falls, Ontario

* photo taken in Washington, D.C

* photos taken on May 16 2010 @ Cylburn Arboretum, Baltimore, MD


* photo taken on August 3 2010 @ University of Guelph Arboretum, Ontario

* photo taken by Milan Havlis, owner of central Europe's premier plant nursery

* historical archive photo

* photo taken on May 9 2015 in Elkridge, MD

* photo taken on June 25 2017 in Columbia, MD

* historical archive photo


'Apiculata'
Light yellow flowers and always double pinnate foliage

'Coral Sun'
Foliage is orange-red in spring turning green during the summer, otherwise similar. Fall color is often spectacular.

* photo taken by Milan Havlis, owner of central Europe's premier plant nursery

'Fastigiata'
Reaching up to 70 x 40 feet with a columnar habit. Very attractive tree! Can be used on narrow streets or to border a property in a "Lombardy Poplar kinda way"

* photos taken on May 6 2010 @ Brookside Gardens, Wheaton, MD



* photos taken on Mar 18 2017 @ Brookside Gardens, Wheaton, MD

* photos taken on Apr 23 2017 @ Brookside Gardens, Wheaton, MD

* photo taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD


'Rose Lantern'
Very attractive fruits mature to red; otherwise similar.

'September'
Large flowers appear 1.5 months later than the species, otherwise similar.

* photo taken on Aug 15 2011 in Columbia, MD

* photo taken on Aug 21 2017 in Columbia, MD

* photo taken on Oct 17 2017 in Columbia, MD

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