Thursday, January 21, 2010

Indigofera - Indigo

A genus of close to 700 species of shrubs and trees. Indigofera is a source of purple-blue dye. They prefer full sun and light well drained soil that is moist during summer, though most Indigofera can tolerate drought. Insect pests and disease are very rare. Deer resistant.
Pruning is usually done either in late winter or after flowering.
Propagation is from seed soaked in warm water before sowing, or from half hardened cuttings. Some can also be reproduced from root cuttings and removed suckers.



Indigofera amblyantha ( Tall Indigo )
A very graceful, airy, open, wiry branched, large deciduous shrub native to central and eastern China. Some records include: fastest recorded growth rate - 5 feet; largest on record - 11 x 18 feet.
The pinnate leaves, up to 7 inches in length, are composed of 7 to 11 oblong leaflets, up to 2 x 0.8 inches in size. The foliage is bright green.
The bright pink to red flowers, are borne in axilliary racemes, up to 6 inches in length, from late spring into November.
Hardy zones 5 to 9 ( tolerating -20 F ) on moderately moist, fertile soil. Tough and drought tolerant. Cut back hard to near ground in March.

* photos taken on June 23 2013 @ U.S. National Arboretum, DC

* photos taken on Oct 17 2013 in Olney, MD


Indigofera australis ( Australian Indigo )
An fast growing, attractively tiered, evergreen shrub native to Australia. Some records include: largest on record - 10 x 10 feet.
The pinnate leaves, up to 4 inches in length, are composed of 9 to 21 leaflets, up to 1 inch in length. The foliage is blue-green above, hairy beneath.
The stunning purple-red flowers, are borne in racemes from late spring into autumn
Hardy zones 9 to 10 tolerating as low as 20 F. Requires acidic soil.

Indigofera cylindrica ( Tree Indigo )
An evergreen large shrub to small tree native to South Africa. Some records include: largest on record - 25 x 10 feet with a trunk diameter of 6 inches.
The pinnate leaves, up to 4 inches in length, are composed of 8 to 14 notch tipped leaflets, up to 0.5 inches long.
The small white, pink to purplish-red flowers, are borne in dense racemes.
Hardy zones 9 to 11

Indigofera decora ( Chinese Indigo )
Also called Indigofera incarnata. A very invasive, low growing, suckering, stolon spreading deciduous shrub reaching a maximum size of 3 x 6+ feet, that is native to China and Japan. It is generally used for groundcover, excellent for large scale commercial sites.
The pinnate leaves, up to 10 inches in length, are composed of 25 to 40 leaflets, up to 2.5 inches in length. The foliage is bright green. The foliage persists late in fall, often remaining green until temperatures drop below 25 F.
The large light pink flowers are up to 0.6 inches in length. They are borne on racemes, up to 10 inches in length, borne all summer into autumn.
Hardy zones 5 to 9 in full sun to partial shade, preferring acidic soil. It is very tolerant of both heat, humidity and drought.

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

* historic archive photo


'Alba'
White flowers, otherwise identical.

'Rosea'
Deep rose-pink flowers, otherwise identical.

Indigofera dielsiana
Also called Indigofera balfouriana. An upright, open, deciduous small to medium-size shrub, native to Yunnan and western Sichuan Provinces in China. Some records include: fastest recorded growth rate - 3.5 feet; largest on record - 6.5 x 5 ( rarely over 5 ) feet.
The pinnate leaves, up to 5 inches in length, are composed of 7 to 11 oval leaflets up to 1 x 0.6 inches in size. The downy foliage is deep green.
The light pink flowers are borne in erect racemes, up to 6 inches in length, from June into September.
Hardy zones 6 to 9 and very drought tolerant. In areas with cool summers, plant against a warm south facing wall. Propagation is from seed in autumn or softwood cuttings taken in summer.

Indigofera gerardiana ( Himalayan Indigo )
Also called Indigofera heterantha. A fast growing, dense, twiggy, upright, arching, deciduous shrub native to the northwest Himalayas. Some records include: 1 st year - 2 x 4 feet; 5 years - 5 x 9 feet; largest on record - 10 x 13 feet. A very beautiful shrub, it also makes an good hedge.
The pinnate leaves, up to 4 inches in length, are composed of 13 to 21 elliptical leaflets, up to 1 x 0.6 ( rarely over 0.5 ) inches in size. The foliage is gray-green.
The very abundant, bright pink to rosy-red flowers, up to 0.5 inches, are borne up to 24 on a dense racemes, up to 10 inches in length. The flowers are borne on current seasons growth from June into September.
Hardy zones 6 to 8 ( zone 4b as a herbaceous perennial...thriving as far north as Ottawa, Ontario ) in full sun to partial shade on just about any well drained soil. If cut to hear ground in late winter, it grow luxuriantly and vigorously when spring comes. Tough as nails, it is extremely tolerant of both heat and drought.
Propagation is from seed sown in fall and also from softwood cuttings taken during summer.

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


* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014


Indigofera hebepetala
A herbaceous perennial to 4 feet in frost prone climates, evergreen shrub to 10 feet in mild climates, that is native to northwest Himalayas.
The attractive pinnate leaves, up to 10 inches in length, are composed of 5 to 15 leaflets, up to 3 x 1.8 ( rarely over 2.5 x 1 ) inches in size.
The pink or red flowers, up to 0.5 inches, are borne in racemes, up to 10 inches in length, from June into October.
They are followed by narrow pods up to 2 inches in length.
The stems are deep brown.
Hardy zones 8 to 11 ( 5 to 7 as perennial ). It is very hardy in warmer parts of England, including at Kew.
Frosted plants should be cut back to ground before new growth emerges in spring.

Indigofera kirilowii ( Kirilow Indigo )
A very dense, rapid growing, deciduous shrub native to Korea, nearby areas of China and the island of Kyushu, Japan. Some records include: 8 years - x 6 feet; largest on record - 6 x 6 feet. It makes both an excellent landscape plant and an attractive tall groundcover to prevent erosion on steep slopes. It is rare to endangered in the wild.
The pinnate leaves, up to 6 inches in length, are composed of 7 to 13 leaflets, up to 2 x 1.2 ( rarely over 1.5 ) inches in size. The foliage is bright green.
The very abundant, rose-pink flowers, up to 0.6 inches long, are borne on racemes, up to 8 ( rarely over 5 ) inches in length, from late spring into early summer.
Hardy zones 4 to 8. Very drought tolerant. Cut back to ground level during winter north of zone 7.

* photos taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014


Indigofera pendula ( Weeping Indigo )
A very fast growing, rare, beautiful, arching, medium-size shrub, reaching a maximum height of 13 feet, that is native to southwestern China.
The pinnate leaves, up to 10 inches in length, are composed of up to 27 leaflets, up to 1.5 x 0.6 inches in size.
The violet-pink flowers are borne on long wisteria-like clusters, up to 18 inches in length, during mid to late summer. The flowers resemble that of Wisteria more than that of other Indigofera.
They are followed by pods, up to 2 inches in length, during early to mid autumn.
Hardy zones 8 to 10.

Indigofera potaninii ( Pink Indigo )
Also called Indigofera szechuensis. A very beautiful medium-size shrub native to southwestern China. Some records include: largest on record - 10 x 13 ( rarely over 6 ) feet
The pinnate leaves, up to 6 inches in length, are composed of 7 to 13 leaflets, up to 1.5 x 0.3 inches in size. The foliage is mid-green above, bright green beneath.
The deep pink flowers are borne in racemes, up to 8 inches in length, June into October.
Hardy zones 4 to 9

* photos taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014


Indigofera pseudotinctoria ( Chinese Indigo )
Also called Indigofera bungeana. A fast growing, small shrub, reaching a maximum size of 3.3 x 3 feet, that is a widespread native of most of China, Korea and Japan. It is found on both grasslands and river plains in its natural range.
The pinnately-compound leaves are composed of 5 to 11 oblong leaflets, up to 1 x 0.6 inches in size. The foliage is downy bright green.
The pink flowers, up to 0.2 inches long, are borne on dense panicles, up to 6 inches in length, all summer long.
They are followed by small pods up to 1 inch in length.
Hardy zones 5 to 8 ( possibly 4 for Liaoning seed source ) in full sun to partial shade on just about any moist, well drained soil. Cut back hard during late winter. It is rarely bothered by insect pests or disease.

'Rose Carpet'
A cultivar, forming a low groundcover shrub, reaching a maximum size of 1 x 4 feet.

* photo taken on 4th of July 2010 @ U.S. National Arboretum, D.C.


Indigofera tinctoria
An evergreen shrub native to tropical Africa and southeast Asia. Some records include: 3 years - 8 feet; largest on record - 14 x 8 feet. It may be grown as a herbaceous perennial, up to 3 feet, further north into frost prone areas, even as far as Maryland.
The pinnate leaves, up to 4.5 inches in length, are composed of up to 13 oblong leaflets, up to 1.2 x 0.6 inches in size. The foliage is mid-green above, hairy beneath.
The pink to light red flowers are borne on racemes, up to 3.5 inches in length. The flowers appear during summer on cooler climates, most of the year in tropical climates.
They are followed by small pods, up to 1.2 inches in length.
Hardy zones 10 to 12 as a shrub, further north as a perennial.

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


* video found on Youtube

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