The Ultimate Guide to Ironweed – What you NEED to know


If you are looking for some late season bloomers that are absolute butterfly magnets, then you must consider Ironweed. The clusters of hairy purple to pink flowers are irresistible to pollinators and in particular large butterflies such as Swallowtails and Monarchs.

This article will be a gardening ‘how-to’ for growing and caring for all types of Ironweed. It will cover a large number of topics. I’ve created the digital table of contents below to help you in your learning about this wonderful plant:

In this article:

What is Ironweed

Ironweed is a common name given to 25 species of wildflower of the Vernonia genus that are native to North America. They are perennials that grow from 2-10′ tall in full sun, and bloom approximately 1 month in late-Summer to Fall. An ecologically important plant, it attracts numerous bees and butterflies.

Although there are numerous species, the flowers all have similar forms leading them to be referred to in general as ‘Ironweed’. Some of the more common Ironweed Species with large distributions within North America include the following:

  • Vernonia baldwinii, commonly known as “Western Ironweed”, grows 3-5′ tall in full sun and dry to medium-moist soil and is hardy from zones 5-9. It’s primary native range is from Texas / Louisiana North to Nebraska and Iowa. This is one of the more drought tolerant Ironweed species.
    • Native Range of Vernonia baldwinii (click on image to enlarge)
  • Vernonia gigantea is commonly known as “Giant Ironweed” can grow 5-10′ tall in full sun to partial shade and moist to medium-moist soil. It’s primary native range is from Texas to Florida North to New York and Iowa. It is hardy from zones 5-8.
  • Vernonia Glauca has several common names including “Appalachian Ironweed”, “Broadleaf Ironweed”. It grows 3-5′ tall along mountain streams in full sun to partial shade. Tolerant of clay and growing best in moist to medium-moist soil, it’s native range primarily follows the Appalachian Mountains from PA/NJ to Alabama.
    • Native Range of Vernonia glauca (click on image to enlarge)
  • Vernonia fasciculata is commonly known as “Common Ironweed”, “Smooth Ironweed”, or “Prairie Ironweed”. As a general rule it grows 2-4′ tall in full sun and medium-moist to wet soil. It’s native range is generally from North Dakota to Oklahoma, East to Ohio and Michigan and is hardy from zones 4 through 9.
    • Common Ironweed, photographed in Jackson County Iowa August 2020 (click on image to enlarge)
    • Native Range of Vernonia fasiculata (click on image to enlarge)
  • Vernonia missurica, commonly known as “Missouri Ironweed”. It grows 3-5′ tall in full sun and moist to medium-moist soil and is hardy to zones 6-8. Possibly the prettiest or showiest of the Ironweeds, it’s native range primarily is throughout the Mississippi River valley and adjacent areas.
    • Native Range of Vernonia missurica (click on image to enlarge)
  • Vernonia noveboracensis, commonly known as “New York Ironweed”, grows 4′-8′ tall in full sun to partial shade and moist to medium-moist soil. Tolerant of clay, you can often find it near water or wetlands, but does well in an open prairie too. It is hardy to USDA growing zones 5-9.
    • Photographed in Southern Pennsylvania August 2021 (click on image to enlarge)
    • Native Range of Vernonia noveboracensis (click on image to enlarge)

Ironweed Quick Reference Table

Scientific NamesVernonia baldwinii, Vernonia fafsciculata, Vernonia gigantea, vernonia glauca, Vernonia missurica, Vernonia noveboracensis
Common Name(s)Ironweed, Missouri Ironweed, Western Ironweed, Giant Ironweed, Upland Ironweed, Prairie Ironweed, New York Ironweed
Native Range, USDA ZoneUSDA Hardiness Growing Zones 4-9
Bloom TimeLate Summer to Fall
Bloom Duration, ColorApproximately 1 month, purple/pink flowers
Height2-10′ (60-300 cm)
Spacing / Spread2-4′ (60-120 cm)
Light RequirementsFull Sun to partial shade
Soil TypesLoam, Clay, Silt
MoistureAs a general rule Ironweed prefers moist soil to medium-moist soil for most
Fauna Associations / Larval HostsNumerous species of bee and butterfly will visit Ironweed. It is extremely popular with pollinators.
Sources – [1], [2], [3], [4], [5], [6]

Origin of the name “Ironweed”

The common name “Ironweed” has been attributed to the rigid stalks that tend to stay upright in all conditions, as well as the color of the fading flowers, as they appear to ‘rust’. [9]

Ironweed Native Range

The 25 different species have colonized many parts of Eastern North America, making the Native Range of Ironweed go from Texas-North Dakota, East to the Atlantic Ocean.

Native Range of Ironweed Species in North America [1] [2] [3] [4]

What are the Benefits of Ironweed

Beauty

Tall clusters of purple flowers give Ironweed a truly striking appearance in the garden. If several plants are present, you get a ‘mass bloom’ effect that gives a dark purple to pink hue. Furthermore, the foliage is attractive by itself as well.

Pollinators

Ironweed has become one of my most reliable plants for attracting butterflies. The blooms of Ironweed produce significant amounts of nectar that attract butterflies. Additionally, the purple color makes the Ironweed flowers stand out to pollinators.

In my own gardens, I regularly see multiple large Swallowtail and Monarch Butterflies visiting the clusters of purple blooms. And what is even cooler is that the butterflies will stay there for a long time – it isn’t a causal visit!

Birds

Ironweed is a valuable Winter food source for birds. The seed heads of Ironweed are attached to a stiff stem and can withstand the elements, standing tall into winter. This provides a natural bird feeder for your yard.

Late Bloom Time

On average all Ironweed species bloom in late Summer to early Fall for 4-6 weeks, which can fill bloom gaps in flower gardens. The showy pink to purple flowers add a late Summer ‘pop’ to your landscape.

Ironweed identification and characteristics

Obtaining a positive ID on an “Ironweed” species can be quite challenging, as there are 25 species and they all share many similarities & characteristics. Furthermore there is frequent hybridization between species [2] [6]. This occurs so much so that most people just refer to the showy flowers as ‘Ironweed’.

So, the attributes below can help you to identify ‘Ironweed’. But at the end I do include a reference table for some of the more common/widespread species and their botanical attributes.

To properly ID an Ironweed species one generally needs to make a close inspection of the flowerhead, and even trained botanists can confuse species due to within species variation. My own preference is to note the bloom time, size, and compare the geographic location & growing conditions to make an approximate ID.

Stalk

As a general rule Ironweed will have an erect stalk 2-8′ tall that is green to red/brown in color. It will not have branching except at the flower head. Typically it is round with vertical ridges.

Ironweed Leaves

All Ironweed will have single (simple) alternate leaves. In general they are lanceolate, elliptical, or ovate/oblong in shape and 2-6″ long. They are dark green on top, and lighter green underneath with serrated or toothed margins.

Ironweed Flower

Ironweed Flowers are clusters or flat-topped clusters (corymb) of pink-purple disk flowers. These clusters can range from 3″ diameter up to 16″ diameter. The individual flower, which is a cluster of tiny tubular flowers is usually 1/2″-3/4″ tall by 1/4″ diameter. It is very similar in size to a pencil eraser before blooming.

The flower structure of an individual Ironweed flower is very unique. I like to think of it as a daisy-like flower without any petals. You just have the center part, which consists of 10-40 little florets. The florets are small tubes that usually have 5 lobes.

After blooming has finished, the tubular lobes form small tufts of hair. And seeds form in the bracts. In-turn, these seeds are carried by the wind and dispersed.

Root

The root system of Ironweed is typically fibrous rhizomes and can form small colonies. The main root mass can be shaped like a paw. [9]

Quick ID Reference Guide to different species of Ironweed (vernonia)

Species Common NameStalk / StemLeavesFlower Head ShapeSoilMoisture
Vernonia baldwinii Western Ironweed, Baldwin’s IronweedSingle stalk with no branches until flower head. Covered in short white hairs Roughly 2.5′ – 5′ tallAlternate, 2-6″ long and 1-2″ wide, non-symmetrical lanceolate or elliptic-ovate shape, coarsely serrated margins and hairy, Flat-topped panicles, with roughly 15-35 pink/purple florets. Flowers are approximately 1/2″ diameter with individual florets having 5 spreading lobes. The base of the flower has bracts that curl outwards.Clay, Sand, Loam, RockyMedium-moist to dry conditions
Vernonia gigantea Giant Ironweed, Tall IronweedUnbranched except for near the flowers, tall, light green to purple green, with few hairs or smooth and cylindrical cross section. 3-7′ tallAlternate leaves that are up to 9″ long by 1/3 as wide. Narrow ovate to elliptic in shape with toothed margins. Large 6-16″ diameter panicles (flat-top cluster) of pink/purple flowers. Each individual disk floret will have 5 curling lobes.Silt-loam, Loam, Sandy-loam, Clay-loamMedium-moist to dry conditions
Vernonia Glauca Appalachian Ironweed, Broadleaf IronweedUpright and unbranced with a round shape & vertical ridges, green. 2-5′ tall.Alternate simple leaves that are elliptical or lanceolate in shape and 5-7.5″ long by 1.3″-3″ wide w/ serrated edges. Flat-top cluster of 32-48 pink-purple flowers. Inner bracts lanceoolate-ovate, outer lanceolate. Flowers in July, earlier than V. noveboracensis. Found in upland woods.Loam, Sand, ClayMoist to medium-moist
Vernonia fasciculata Common Ironweed, Smooth IronweedRound, hairless, unbranched (except at flowerhead) stalk that grows 2-4′ tall. Can be white, light-green, or red in color.Alternate leaves 2-5″ long and 1/2″ wide that are narrow lanceolate or linear with serrated margins.A tightly grouped flat-top cluster of 15-30 pink-purple flowers. Below the pink/purple lobes are overlapping bracts, similar to fish scales similar to Missouri IronweedLoam, clay-loam, and fertileMoist soil & can tolerate occasional flooding
Vernonia missurica Missouri IronweedSingle stalk, red in color and has small white hairs. It is unbranched until flower head. 3-6′ tallAlternate dark green leaves that are ~6″ long by 2″ wide. Lanceolate shape with serrated margins, hairs on underside.Composite pink/purple flowers (corymb) that are 1/2″-3/4″ diameter. Flat flower head with 30-60 blooms. Red-to-brown stems to flowers, with overlapping bracts below the flowers.Loam, clay-loam, sandy-loamMoist to medium-moist soil
Vernonia noveboracensis New York IronweedGreen to reddish hairless stem with round with vertical ridges. Unbranched except at flowerhead. 3-8′ tall.Simple alternate leaves that are lanceolate in shape 5″-11″ long by 0.5-2″ wide. Serrated margins (edges). 3-6″ clusters of flowerheads with 30-65 flowers. Bracts trinagular-ovate. Flowers in August, mainly found in low wetlands, stream or pond banks.Loam, ClayMoist to medium-moist. Can tolerate occasional flooding.
Sources – [1], [2], [3], [4], [5], [6] [12]
Visual Lifecycle Guide for Ironweed

Ironweed throughout the seasons

In general, Ironweed can be readily identified throughout the seasons when not blooming. One just needs to know what to look for. I’ll attempt to give you that information here.

What Ironweed looks like in Spring

Ironweed emerges in mid to late Spring with dark green shoots. The leaves that develop will generally have serrated or toothed edges and be lanceolate or elliptical in shape. Expect rapid growth from emergence (early May in zone 6) through the 4th of July.

Ironweed emerging in Spring

What Ironweed looks like in Summer, before Bloom

By mid-Summer Ironweed will be very erect with a strong, sturdy vertically ridged, un-branched stalk. The simple alternate leaves will be present with their serrated or toothed margins. Buds may be beginning to form in the center at the stalk with minor branching. These buds will look like closed pods.

What Ironweed looks like in Winter

Post blooming, Ironweed will generally keep it’s seed into early to mid-Winter. The seeds are generally grasped tightly by the bracts. Seed pods will look like fuzzy/hariy pencil erasers, and are of similar size.

Ironweed seedheads standing tall, silhouetted against the sky.
Ironweed seed head in winter

Ironweed versus Joe Pye Weed

People frequently confuse Ironweed and Joe Pye Weed, as they do look alike. This is understandable, as they both have somewhat similar flowers and their bloom times overlap. But the leaves, buds, and flower of Joe Pye Weed and Ironweed are all distinctly different.

However, there is one absolute key difference between Joe Pye Weed and Ironweed….Joe Pye Weed has whorled leaves while Ironweed has alternate leaves.

What this means is that Joe Pye Weed will have three or more leaves at the same height location on a stalk, all clasping & arrayed around the stem. While Ironweed will have Alternate leaves, meaning you will have a single leaf on the stem, then another rotated above it. This difference alone should be enough to differentiate Joe Pye Weed from Ironweed before flowering.

Grow and Care for Ironweed

If planted in it’s preferred growing conditions, Ironweed will not require any special care. It is generally free of disease and herbivore predation.

Ironweed Spacing

As a general rule, you should plant Ironweed plants at least 2′ apart. Ironweed plants generally like to have 2-4′ spacing between plants. This allows the plants to reach their full potential without crowding each other out.

Sunlight Requirements

As a whole all species of Ironweed will grow best in full sun, which is at least six hours of direct sunlight per day. There are some specific species that can tolerate partial shade, but all Ironweed will do well out in the open, directly exposed to sunlight.

Three Tiger Swallowtail butterflies on Ironweed in late August.

Soil Requirements

Ironweed can tolerate a wide variety of soils as long as they drain well. Most loams/silt are perfectly suitable for growing just about any species of Ironweed. Furthermore there are several common varieties that can tolerate clay and moist soil.

If you are unsure if you have well drained soil, you can learn how to test it here.

One additional piece of valuable information is that Ironweed is Juglone tolerant, meaning it can grow near Black Walnut trees.

Ironweed pH requirements

Like most native plants, Ironweed prefers slightly acidic soil with a pH level of 6.8 or less. But, it is quite adaptable for neutral pH sites as well.

Moisture Requirements

All Ironweed will grow well in medium-moist soil. Most Ironweed do not like drought, so you may need to provide supplemental water depending on where you plant it.

Natural Habitat of Ironweed

The types of areas one is likely to naturally encounter Ironweed is in wetter areas near ponds, streams, and wetlands. Additionally, you can find Ironweed growing along roadsides, railroads, and in medium-moist prairies.

How to Grow Ironweed from Seed

Ironweed can be readily be grown from seed. But you need to plant it how mother nature does! That means shallow planting depth and a cold moist stratification period.

Ironweed seeds

Studies have shown that cold stratification of Ironweed seeds will increase the germination rate from 16% to 40%. [7] [8]. The easiest way to achieve this cold stratification is by Winter Sowing. However, you can achieve the stratification using the refrigerator.

Before you begin, you will need to gather or purchase some seed. I’ve had the best luck and highest germination rates when I stored my seed in the refrigerator in sealed plastic bags.

  1. Prepare containers for Winter Sowing or Seed Starting. It doesn’t matter whether you use milkjugs or traditional containers when you Winter Sow, as long as you ensure the seeds don’t dry out. (See our step by step guide to Winter Sowing here).
  2. Plant Ironweed seeds to a depth o 0-1.5 mm. In order for the seed to meet it’s cold stratification requirements, the seed needs good contact with the soil. I sprinkle seeds on moist potting soil, and then press them into the soil. Then, I just lightly dust the seeds with more moist potting soil.
  3. Keep the seeds moist. Throughout the Winter you need to periodically check your containers to make sure they don’t dry out. This is more of an issue if you used a small 6-pack seed starting tray rather than a milk jug. But pick up the containers periodically to make sure they have some moisture present. Water if needed.
  4. Place containers where they get morning sun and afternoon shade. This step is very important! Once outside temperatures regularly get above 50F, move the containers where they will get sun from morning until lunch time.
  5. Wait for germination. Ironweed seeds tend to germinate in mid to late Spring. So you must be patient! Ironweed seeds germinate later than other native species.
Ironweed Seedlings

How to direct sow Ironweed seeds

Ironweed can be direct sown in the Fall or Winter before the ground is frozen. Rough up / disturb the soil where you want to grow Ironweed. Then, scatter Ironweed seed over the area. Finally, walk over the area you scattered the seed to press the seed into the soil.

As described in the previous section, Ironweed seed needs to have good contact with the soil and a cold moist stratification period. Pressing the seed into the soil ensures the former, while sowing in Autumn/Winter ensures the latter.

How long to establish Ironweed from seed

As a general rule, you can expect Ironweed to bloom in it’s second year after germinating the seed. Like many native perennials, Ironweed will typically spend it’s first year from germination establishing a healthy root system.

Ironweed Control and Invasive

Since the flowers of Ironweed produce numerous seeds attached to small feathers, Ironweed can become aggressive or invasive in formal gardens. The most effective way to control Ironweed is to deadhead and cutoff the blooms as soon as they have faded before seeds form. As the saying goes, and ounce of prevention is worth a pound of cure.

But to control Ironweed that has gone to self-seeded, one needs to just pull unwanted seedlings. In Spring or Summer water the area thoroughly to soften the soil, then use a simple weeding tool or flathead screwdriver to loosen the soil. Finally, just pull up any seedlings you find.

Ironweed that is aggressively invading a pasture.

Wildlife, Pests, and Diseases associated with Ironweed

Pollinators

The flowers of Ironweed produce lots of nectar that attracts numerous long-tongued bees, bee-flies, butterflies & skippers. The blooms are busy from morning until dusk with insects and attract lots of activity.

Ironweed hosts the American Lady (Vanessa virginiensis) and many other caterpillars feed on the foliage. The caterpillars of several borer moths, the pyralid moths feed on the stems and roots. Additionally there are other insects that will form galls on the stems near flowers, and several other insects that feed on the leaves.

The insects supported by Ironweed play an important role in the food chain, as they in-turn are food for birds and other fauna. Although some people may feel that foliage damaged by insects is unsightly, it is a sign of a healthy ecosystem. You plants are feeding all the insects, birds, and the rest of the food chain.

Finally, I can personally attest that Ironweed is one of the most reliable plants that attract butterflies in my gardens. They will truly be filled with skippers, small bees, and large Swallowtail and Monarch butterflies while in bloom. For reference, I have about 3-5 large plants.

Skipper on Ironweed

Deer and Ironweed

In general deer and rabbits don’t bother established Ironweed plants as the foliage is quite bitter. It is known as one of the last plants to be eaten by herbivores.

However, I have personally had young plants eaten when emerging in the Spring. So, until established it is a good idea to protect younger seedlings with Liquid Fence.

Disease

As a general rule Ironweed isn’t significantly effected by disease. Late in the season foliage can be cosmetically effected by mildew, but this is not fatal to the plant.

Where you can buy Ironweed

Many types of Ironweed can be purchased at specialty nurseries that deal in Native Plants. You can find native plant nurseries near you on our interactive map.

Where to buy seeds

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

Ironweed plant uses

Garden Uses

Many types of Ironweed can be suitable for a formal garden setting. While some native plants tend to flop over when planted in a garden setting, Ironweed generally stays erect. This makes Ironweed a good choice for the back of a perennial garden, or border garden.

Additionally, if you have a wildflower area, Ironweed can be an excellent choice. It’s adaptability to most soils allow it to be widely utilized.

Ironweed for Butterfly Gardens

If you have any interest in attracting butterflies to your gardens, Ironweed is an absolute “must have” plant. It is truly one of the busiest flowers in my gardens, frequently bringing in 3-5 large Swallowtails or Monarch Butterflies. And the butterflies are not just ‘here and gone’. They will spend 30 minutes to over an hour feeding on the sweet nectar that Ironweed produces.

What Ironweed is best for a formal flower garden?

Vernonia glauca, aka Broadleaf Ironweed is one of the better choices of Ironweed for a formal flower garden. It’s smaller size of 2-4′ mean that it can blend with many other species of flower in a formal, mulched flower bed. And the flowers will still produce the sweet nectar that butterflies crave.

Ironweed Companion Plants

Being very adaptable to soil conditions, there are many plants that can pair well with Ironweed. Some plants that will bloom concurrently with Ironweed, and like similar growing conditions include the following;

Ironweed growing with Purple Coneflower and False Sunflower.

Other plants that share similar growing conditions as Ironweed, but bloom before or after would include the following;

Deadheading Ironweed

While many species perennial can be deadheaded to prolong the blooming period, in general Ironweed won’t produce a significant round of blooms via deadheading. However Ironweed can self-seed in the right conditions, so it is generally a good idea to deadhead Ironweed to prevent self-seeding.

Medicinal Properties of Ironweed

Ironweed has been used by medicinally for many years. A medical literature review from 2013 found over 100 species of Ironweed (worldwide) used to treat over 40 diseases and/or health conditions that can effect humans. [10] This study examined all members of the Vernonia genus, not just those native to North America.

Native American Uses of Ironweed

Documentation exists of 20 uses of Ironweed by 5 different tribes ranging from food, material, and medicinal. [9] [11]

Medicinal Uses by Native American.

The Cherokee tribe utilized Ironweed for post childbirth medicine and for menstrual problems in women. Also a root infusion was used to treat toothaches, stomach ulcers or hemorrhages. [11]. The Cherokee would make a medicinal tea.

Roots were also tenderized and boiled, the fumes or applied directly to treat sore legs or back. And the Natchez used Ironweed to cure dysentery. [9]

Edible Uses of Ironweed

In addition to medicinal uses, flowers of Ironweed were used as chewing gum as a sweet candy by the Kiowa tribe.

Other Native American Uses of Ironweed

The stalks and fiber was used as bedding when traveling. Members of the Kiowa tribe would pile the stalks approximately 6″ tall to use as a bed. [11]

Find more Native Plants Here

References:

[1] – Jonely, Janna. “Vernonia noveboracensis-New Crop Summary and Recommendations.” (2012).

[2] – Jones, Samuel B. “The Taxonomy of Vernonia acaulis, V. glauca and V. noveboracensis (Compositae).” Rhodora 72.790 (1970): 145-163.

[3] – Jones, Samuel B. “Taxonomy of the narrow-leaved Vernonia of the southeastern United States.” Rhodora 66.768 (1964): 382-401.

[4] – Gleason, Henry Allan. “Taxonomic studies in Vernonia and related genera.” Bulletin of the Torrey Botanical Club 46.7 (1919): 235-252.

[5] – Faust, W. Zack. “A biosystematic study of the Interiores species group of the genus Vernonia (Compositae).” Brittonia 24.4 (1972): 363-378.

[6] – Jones Jr, Samuel B. “Hybridization of Vernonia acaulis and V. noveboracensis (Compositae) in the Piedmont of North Carolina.” Castanea (1972): 244-253.

[7] – Greene, H. C., and John T. Curtis. “Germination studies of Wisconsin prairie plants.” American Midland Naturalist (1950): 186-194.

[8] – Sorensen, J. T., and D. J. Holden. “Germination of native prairie forb seeds.” (1974).

[9] – Jackson, Jason Baird. “Customary uses of ironweed (Vernonia fasciculata) by the Yuchi in eastern Oklahoma, USA.” Economic Botany 54.3 (2000): 401-403.

[10] – Toyang, Ngeh J., and Rob Verpoorte. “A review of the medicinal potentials of plants of the genus Vernonia (Asteraceae).” Journal of ethnopharmacology 146.3 (2013): 681-723.

[11] – North American Ethnobotany Database, Vernonis genus, accessed 26DEC2021. http://naeb.brit.org/uses/search/?string=vernonia

[12] – Duncan, Wilbur H., and Marion B. Duncan. Wildflowers of the eastern United States. Vol. 20. University of Georgia Press, 2005.

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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