Sunday, January 17, 2010

Amorpha - False Indigo

A genus of 15 species of shrubs that are part of the larger Legume family and are native to North America.
They prefer full sun to partial shade on just about any well drained with sufficient summer moisture. They are rabbit and deer resistant. Insect pests or disease are very rare. Propagation is from the hard seeds which should be sandpapered before sowing. The seeds can also be treated by soaking in sulfuric acid for 8 minutes then left in hot water. They can be then placed in a plastic bag of half moist sand and half peat then placed in the refrigerator for 3 months. Once they are then sown in a warm location, they often germinate within a week. Cultivars can also be reproduced from hardwood cuttings in winter or half hardened cuttings taken in summer.

* photo of unknown internet source

Amorpha californica ( California Indigo )
A medium-size shrub reaching a maximum size of 13 x 16 feet, that is native to southwest Oregon and much of California through more restricted to coastal mountains in the south. It is endangered in Oregon.
The pinnate leaves, up to 8 inches in length, are composed of up to 25 oblong leaflets, up to 1.5 inches in length. The attractive aromatic foliage is blue-green.
The violet-purple flowers are borne on upright spikes up to 3 inches in length.
Hardy zones 6 to 10 in partial to full shade on well drained soil. It is very tolerant of summer drought and pure sand. Propagation is easy from seed which requires no pretreatment. It grows best in Mediterranean climates where annual precip exceeds 26 inches.

Amorpha canescens ( Lead Plant )
A deep-rooted, upright, rounded, small shrub to around 3 feet that is native to dry sandy prairies and open woodlands from Saskatchewan to Kenora, Ontario to southern Ontario to Guelph, Ontario; south to central New Mexico to central Texas to Arkansas to Indiana. Some records include: 3 years - 3 feet; largest on record - 5 x 5 feet. In northwestern Ontario; it is usually found in bur oak savanna. It is extinct in Montana; endangered in Manitoba, Ontario, Michigan and Arkansas. It occurred sporadically at Detroit, Michigan during the 1800s.
The pinnate leaves, up to 6 inches in length, are composed of 15 to 51 oblong leaflets, up to 1 inch in length. The foliage is silvery-gray due to the fine covering of hairs. The leaves turn dull yellow during autumn. The leaves can be used to make a pleasant tea, and were by the Oglala Indian Tribe.
The bluish-purple flowers are borne in dense narrow clusters, up to 10 inches in length, during early to mid summer.
Hardy zones 2 to 6 in full sun on well drained soil. The deep root system reaching up to depths of 4 feet contribute to its extreme drought tolerance. It is also very drought tolerant. Prune back hard every other year to keep it from becomming leggy.

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

* photo of unknown internet source

* photos taken on June 30 2013 @ U.S. National Arboretum, DC

* photo taken on July 11 2014 in Washington, DC

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

* photos taken on Aug 24 2017 @ U.S. Botanic Garden, Wash. DC.

Amorpha fruticosa ( False Indigo )
A fast growing large shrub native to river valleys and prairies in central and eastern North America ( from northeast Wyoming to southern Manitoba to the western tip of Lake Superior to Chicago, Illinois to northeast Ohio to central New Jersey; south to southern California to southern Florida ). It is endangered in Manitoba. In the Windsor/Essex County, Ontario region; it occurred locally bordering marshland along the lower Canard River Valley during the 1800s and persisting into the 1980s. It sometimes forms widespreading thickets on floodplain soils. Some records include: first year from seed - 24 inches; Some records include; fastest recorded growth rate - 3 feet; 3 years - 4 feet; 6 years - 7 feet; largest on record - 20 x 40 ( usually half that ) feet.
The pinnate leaves, up to 16 ( rarely over 11 ) inches in length, are composed of 9 to 33 oblong leaflets, up to 2 x 0.5 inches. The foliage is bright to medium green.
The small, violet-purple flowers, up to 0.3 inches long, are borne on bottlebrush panicles up to 10 inches in length, during late spring and early summer.
Hardy zones
Hardy zones 3 to 9, tolerating as low as -40 F and grows very well on poor dry soils.

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

* photo of unknown internet source

* photos taken on June 30 2013 @ U.S. National Arboretum, DC

* photos taken on July 26 2015 @ Niagara Parks Bot. Gardens, Niagara Falls, ON

* photos taken on May 30 2016 in Annapolis, MD

* photos taken on Jul 19 2017 @ Rideau Hall, Ottawa, ON

* photo taken by Dr. Nick V. Kurzenko @ CalPhotos

* USDA-NRCS PLANTS Database / Herman, D.E., et al. 1996. North Dakota tree handbook

* photo of unknown internet source

* google earth of Amorpha fruticosa in Lasalle, ON

* google earth showing great clump near Colchester, ON

White flowers

Pale blue flowers.

Amorpha herbacea ( Clusterspike False Indigo )
A shrubby perennial, reaching up to 4.5 x 6 feet in size, that is native to the southeastern U.S. ( from southwest Alabama to the Smoky Mountains of North Carolina to the NC coast; south to central Florida. It is endangered in Alabama and Georgia. Subspecies 'crenulata' which occurs in the area of Miami, Florida is critically endangered with less than 1500 plants remaining in the wild.
The alternately-arranged, pinnately-compound leaves are composed of 25 to 35 oblong leaflets up to 1 inch in length. The foliage is hairy and silvery-blue to gray-green.
The white to bluish-purple ( with orange anthers ) flowers are borne on racemes up to 8 inches in length over a long season during late spring to mid-summer.
The stems are purplish.
Hardy zones 5 to 9 in full sun on well drained soil, preferrably sandy. It is extremely heat and drought tolerant.

* photo taken on Aug 23 2014 @ U.S. Botanical Garden, Wash., DC

Amorpha nana ( Fragrant False Indigo )
A dense small shrub only reaching up to 1.7 x 3 feet, that is native to dry prairies from Saskatchewan to Manitoba, south to New Mexico to Oklahoma and Iowa. It is endangered in Saskatchewan, Manitoba, Colorado, Nebraska, Iowa, Oklahoma and New Mexico; extinct in the wild in Kansas. Some records include: largest on record - 5 x 4 feet. It is a great plant to mix with dwarf conifers.
The pinnate leaves, up to 4 inches in length, are composed of 7 to 41 soft-spine tipped leaflets, up to 0.8 x 0.2 inches in size. The attractive fine-textured foliage is vibrant lush green.
The fragrant, bluish-violet to purple flowers, up to 0.3 inches wide, are borne in sprays, up to 6 inches in length, during early summer. They are highly attractive to butterflies and bees.
The young stems are finely hairy at first, turning to red-brown.
Hardy zones 2 to 8 in full sun on moist, light, very well drained soil.


Amorpha nitens ( Shining False Indigo )
A medium-size shrub, reaching up to 10 feet, that is native to open bottomland forests in the southern U.S. ( southeastern Oklahoma to southcentral Missouri to far southern Illinois; south to Louisiana to central Georgia with a separate range in South Carolina ). It is endangered and extremely localized in every state it resides in except for Arkansas. It likely became extinct before 1900 in Missouri and Mississippi. Some records include: 5 years - 6 feet.
The pinnate leaves, up to 8 inches in length, are composed of 7 to 19 oblong leaflets, up to 3 x 1 ( rarely over 2 ) inches in size. The foliage is glossy deep green.
The red to mauve flowers are borne on spikes up to 8 inches in length.
Hardy zones 5 to 9.

Amorpha ouachilensis ( Ouachita Leadplant )
A small to medium size shrub reaching a maximum size of 6.5 x 6 feet, that is native to open woods in the Ouachita Mountains from southeast Oklahoma to central Arkansas where it is endangered.
The foliage is gray-green.
The purple flowers are borne in narrow clusters, up to 8 inches in length, during late spring.
Hardy zones 5 to 7 on dry, well drained soil.


  1. am growing Amorpha Fruticosa. (Started from seed last year. Now reaching about 3 ft). I have 5 plants, which doesn't mean I'll keep them all. It does tend to run, doesn't it ?

    I'm trying to find a spot for them in the garden. I see they can get quite big. I might experiment with trimming but am wondering if it's worth it. What's the life expectancy, do you know ?

  2. I suspect their life expectancy is very long though I have not seen any exact statistics. It is quite possibly that individual clones may sustain themselves for over a century. I wouldn't be surprised they resprout from the rootstock after forest fires. For smaller sites I recommend Amorpha nana and canescens.