A garden is already a living, breathing thing of beauty… but what if it could enlighten, as well as inspire?
If you put an indigo plant in your garden, then you’ll have a work of art and a piece of history on your hands.
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With dense blooms, gorgeous foliage, and a robust toughness, these plants are overflowing with reasons to integrate them into your landscape.
With remarkable versatility, they can excel in many different garden roles, giving you plenty of placement options.
Utilized for thousands of years to yield gorgeous blue dye, species of Indigofera have had a huge impact on humanity as a whole.
Think of the lively lectures you’ll be able to give your houseguests as they inspect your indigo plants!
With a bit of knowledge, you’ll be able to cultivate these plants in no time. Metaphorically speaking, at least – oh, if only plants could grow instantly…
Let’s get ready to rumble:
What You’ll Learn
What Are Indigo Plants?
Technically, “indigo plants” could refer to any of the 750-plus species of trees, shrubs, herbaceous perennials, or annuals within the Indigofera genus.
Here, we’ll cover a handful of popular species that can be grown in the US: I. amblyantha, I. decora, I. heterantha, and I. kirilowii.
That should save you some indecision when deciding which one to grow, right?
The genus name Indigofera can be broken down into the Latin words “indigo” and “fera.”
The former alludes to the distinctive blue dye, while the latter means “to bear,” a reference to how the dye may be harvested from the leaves.
Part of the nitrogen-fixing Fabaceae or legume family, indigo plants collectively hail from eastern and southern Asia.
Typically reaching heights of one to six feet with spreads of three to six feet, they also spread via suckers, beautifully straddling the line between shrub and ground cover.
These plants flaunt pinnately compound, deciduous leaves that are four to eight inches in length, with each bearing seven to 21 leaflets.
These leaflets are ovate to elliptical in shape, and come in various verdant hues, such as blue or gray green, light green, dark green, or medium green.
Pink to rose to purple blooms emerge anywhere from May to September.
These are densely borne on narrow axillary racemes two to eight inches in length, and later give way to leguminous seed pods.
Cultivation and History
Many different species of Indigofera can produce vibrant indigo dye.
Within their foliage lies the organic compound indican which, when fermented, becomes the dye known as indigotin. It’s actually possible to harvest the dye yourself.
Other plants are capable of yielding indigo-colored dye, but Indigofera arguably does it best.
Within the genus, the dynamic duo of I. tinctoria and I. suffruticosa are the all-star players.
The former is native to Asia, the latter originates in Central and South America, and both left their mark on history as highly-valued crops.
Like that of tobacco and cotton, the history of indigo dye is vast and fascinating, and you could easily write a whole book on the subject. I’ll try and keep the recap relatively bite-sized.
Humanity’s use of indigo dye goes way back: archaeologists have discovered indigo-dyed fabrics in Peru from six millennia ago!
In the Old World, ancient evidence of indigo usage includes dyed Egyptian mummy bandages from circa 2400 BCE, as well as recovered seeds and indigo-dyed cloth from the Bronze Age Indus Valley Civilization, which lasted from about 3300 to 1300 BCE.
Whether acquired via trade or by harvesting what grew natively, indigo dye was valued and utilized in many ancient civilizations for dye-making, painting, cosmetics, medicines, and tattooing.
Though it had a long shelf life and didn’t take up much space, indigo dye was expensive to import, hence its nickname “blue gold.”
Due to said expense, Europeans tended to harvest locally-grown woad for blue dye rather than purchasing I. tinctoria-derived dye from India, which was considered a premium product.
The word “indigo” itself is a nod to this: it comes from the Greek indikon, meaning “from India.”
After Vasco da Gama sailed from Europe to India in the late 1400s, newly established trade routes by sea helped global commerce to skyrocket.
By the 1600s, Indian indigo cultivation was on the rise, and European colonies in the Americas were producing indigo of their own via plantation slave labor.
By that point, indigo dye had become much less expensive and more readily available in European markets.
Despite the woad industry’s efforts, I. tinctoria dye had essentially replaced woad dye in Europe by the end of the 17th century.
By 1897, industrial production of cheaper synthetic indigo dye had begun in Europe.
But dye from indigo plants is still valuable to home gardeners and anyone who wants to go au naturel with their dyeing. Plus, they look real pretty in the landscape!
Blue dye and beauty? Historical significance and horticultural splendor? Sounds too good to be true, doesn’t it?
If you wish to acquire additional Indigofera specimens, your best avenues of attack are sowing seeds, taking semi-hardwood cuttings, or simply transplanting a nursery specimen.
If the idea of genetic diversity excites you, then sowing seed is definitely the way to go. Who knows, you could even end up with a super cool mutation!
If that interests you, learn more about propagating Indigofera from seed in our guide.
In the summertime, take three- to six-inch cuttings from the ends of healthy shoots with a sterilized blade.
Take the lower half of each cutting, defoliate it, and dip it in a rooting hormone such as Bonide’s IBA rooting powder, available from Arbico Organics.
For each cutting, fill a four-inch container with a 50:50 mix of peat moss and perlite.
Moisten the media and stick the cuttings in, de-leafed ends first. Place the containers near a sunny window where they can receive bright, indirect light.
Keep the rooting medium moist. If you want to check for rooting, give the cuttings a gentle tug to see if they resist.
For extra credit, give the containers a quarter turn each day to prevent lopsided growth.
Repot as needed, if the cuttings begin to outgrow their containers. Come springtime, the plants should be ready for hardening off, provided their roots are sufficiently strong.
On a pleasant day, leave the cuttings outside for a full 30 to 60 minutes before bringing them back inside.
Add an additional half to a full hour each following day, until the plants can remain outside full-time. At this point, you’ve got the green light for transplanting!
Prepare a moderately fertile, well-draining site with a pH of 7.0 to 8.0 for each transplant, spaced far enough apart to at least account for the plant’s anticipated mature spread.
Dig holes that are at least the width and depth of the transplant’s root system.
Lower the transplants in, backfill with soil, and thoroughly water them in. Keep the soil moist until the transplants become established.
How to Grow
These general recommendations should be applicable for most, if not all species of Indigofera mentioned above that are suitable for cultivation in the US.
But you may have to deviate a bit, depending on which one you’re growing.
Climate and Exposure Needs
An indigo plant needs to be situated in USDA Hardiness Zones 5 through 8, and exposed to full sun.
In especially warm or humid areas, a bit of afternoon shade can be helpful. If possible, provide shelter from harsh winds.
Harsh winters can damage branch tips, so be sure to play it safe if your plants are growing in Zone 5.
See if you can provide a warmer microclimate by situating your plants on southern-facing slopes or by the south sides of structures.
For an indigo plant, well-drained soil with average fertility is just what the doctor ordered.
Ensure that the pH is somewhere between 7.0 and 8.0, neutral to slightly alkaline, and you’re golden.
Water and Fertilizer Needs
You’ll want to deeply irrigate the soil whenever the top inch feels dry.
Many established indigo plants possess some degree of drought tolerance, so don’t stress if you ever slack a bit on watering.
Additionally, make sure to apply some organic, all-purpose fertilizer each spring.
For a 5-19-12 NPK granular fertilizer that’s chock-full of secondary and trace nutrients as well as the chief macronutrients, try Osmocote’s smart-release fertilizer, available in eight-pound bags from Amazon.
- Provide full sun exposure.
- Ensure the soil is well-draining, with a pH of 7.0 to 8.0.
- Water whenever the top inch of soil feels dry.
Pruning and Maintenance
Indigo plants often behave like herbaceous perennials in Zones 5 or 6, in that they can die back to the ground in winter before reemerging in spring.
Keep up aesthetics and help foster new growth by cutting stems to the ground or trimming last year’s growth back to the first living node in late winter to early spring.
For plants that maintain living, aboveground shoots year-round in warmer climates, cutting back isn’t necessary. But it’s always a smart move to prune away any dead, dying, or diseased structures.
Add a few inches of a light mulch such as straw, wood shavings, or shredded leaves to help retain moisture, stabilize the soil temperature, and protect the plant from harsh winter conditions.
Come spring, remove the mulch so new shoots are free to emerge.
To prevent unwanted spread, clip suckers as soon as you happen to notice them.
Species to Select
Let’s take a closer look at what makes each of the species alluded to above so unique and special.
If any of them tickle your fancy, you’re sure to find them available from select nurseries, online vendors, or even at horticultural shows.
Native to China and Japan, Chinese indigo flowers heavily with pink blooms, even in moderate shade.
Hardy in Zones 5 through 8, I. decora reaches a max height of two and a half feet with a width of four feet.
Notably, the dark green leaflets of this species are a bit more lance-shaped than those of the other plants on this list.
Plus, it can tolerate a higher pH! Cool cultivars include the white-flowering ‘Alba’ and rosy-bloomed ‘Rosea.’
Hailing from Afghanistan, Pakistan, and Tibet, I. heterantha wields gray-green to blue-green foliage alongside rosy purple blooms.
Hardy in Zones 5 to 7, this species is also tolerant of alkalinity, and can even handle clay soils. With a height and spread of four to six feet, this one’s a big boy, relatively speaking.
Native to China, Japan, and Korea, I. kirilow is tolerant of alkalinity and a variety of soils, and reaches a height and spread of two to three feet.
Hardy in Zones 5 to 8, this plant has bright green, football-shaped leaflets and rose colored blooms, and its golden fall color is just icing on the cake!
A Chinese native, I. amblyantha lives up to its name with its rosy pink blooms beaming alongside gray-green, oval-shaped leaflets.
Hardy in Zones 6 through 8, this shrub reaches heights and widths of four to six feet, and grows in a notably rounded form.
While it lacks appreciable fall color, the flowers more than make up for it.
Managing Pests and Disease
Along with yielding fantastic dye, indigo plants bless us with their lack of serious pest and disease problems. You read that right: you don’t have to worry all that much about Indigofera health care!
“Don’t worry” doesn’t mean “don’t care,” though. You should still use sanitized tools, clean soils, and only work with disease-free specimens.
Those gardening habits will serve you well when you work with the rest of your plants too.
As shrubs that can also behave like ground covers, indigo plants are quite versatile.
Their shrubbiness is fantastic for use in masses, hedges, and borders, while their spreading tendencies allow them to beautifully perform on slopes, woodland floors, or anywhere else you want a small shrub to colonize.
But their flowers make them stand out anywhere they end up. And of course, you can always harvest them to try your hand at dyemaking!
Quick Reference Growing Guide
|Plant Type:||Woody deciduous shrub (herbaceous perennial in some Zones)||Flower/Foliage Color:||Reddish-orange/grayish-greePink, rose, violet/green|
|Native to:||Eastern and southern Asia||Maintenance:||Low to moderate|
|Hardiness (USDA Zones):||5-8||Tolerance:||Alkaline soils, clay soils, drought, heat (varies depending on species)|
|Bloom Time:||May to September, depending on species||Soil Type:||Moderately fertile, moist|
|Exposure:||Full Sun||Soil pH:||7.0-8.0|
|Time to Maturity:||5-20 years||Soil Drainage:||Well-draining|
|Spacing:||Width of mature spread||Attracts:||Butterflies, bees, wasps|
|Planting Depth:||Depth of root system (transplants)||Uses:||Border, cottage garden, dyemaking, ground cover, grouping, hedge, mass planting, rock garden, slopes, specimen, woodland area|
|Common Diseases:||Root rot||Species:||Amblyantha, decora, heterantha, kirilowii, tinctoria|
Don’t Forego Indigo!
There’s a plethora of garden plants out there, each one demanding immediate placement in your garden.
But as you browse and think over which to utilize next, don’t pass over the humble indigo plant.
I mean, how many plants are tough, stunning, dye-yielding, and stuffed to the gills with a rich, millenia-spanning history? Not enough, I say… this one’s a keeper, folks.
Questions, remarks, fun indigo factoids I may have missed? Put ’em all in the comments section below!
“Bean” yearning for some more leguminous guides? Check out these other members of the Fabaceae family: