New York Ironweed (Vernonia noveborecensis) Plant Profile

New York ironweed

The Spruce / Letícia Almeida

Growing up to seven feet tall and three to four feet wide, New York Ironweed—otherwise known as Vernonia noveborecensis—is a long blooming, perennial wildflower that's commonly found in wet meadows and pastures, banks of streams, low-lying woods and marshes. A member of the Aster family, New York Ironweed has a wide-ranging native area, reaching from New Hampshire to the Florida panhandle, as well as Kentucky and Alabama.

New York Ironweed is known for its distinctive appearance: Not only is it an extremely tall plant that can tower over other wildflowers, but it has bright purple disc florets and numerous, lance-shaped leaves. During the growing season, from July to September, generally, butterflies, bees, and other pollinators flock to the New York Ironweed for its nectar. Out of season, the New York Ironweed's tall, dead stalks provide sturdy perches for migrant birds. If you're concerned with deer damaging your garden, Ironweed plants would make an excellent pick, as they're deer resistant.

Due to its larger size, the New York Ironweed is best-suited for large gardens, butterfly gardens, meadows, wildflower gardens, prairies, or perennial borders. On an even larger scale, the New York Ironweed can protect mass plantings from soil erosion.

Botanical Name Vernonia noveboracensis
Common Name New York Ironweed 
Plant Type Perennial wildflower
Mature Size 4 to 7 feet tall and 3 to 4 feet wide
Sun Exposure Full or partial sun
Soil Type  Sandy or clay soil
Soil pH Acidic, neutral, or alkaline
Bloom Time July through September
Flower Color Purple
Hardiness Zones Zones 5 to 9
Native Area New Hampshire to the Florida panhandle, Kentucky, Alabama
New York ironweed in a garden
The Spruce / Letícia Almeida 
closeup of New York ironweed
The Spruce / Letícia Almeida 
New York ironweed cluster
The Spruce / Letícia Almeida 
closeup of New York ironweed
The Spruce / Letícia Almeida 

How to Grow New York Ironweed

Ironweed can be grown from seeds or from a plant purchased from your local nursery.

If you choose to grow Ironweed from seeds, there are some important guidelines you need to follow:

  • Sow the seeds in the fall, planting them no deeper than 1/8th of an inch in the soil. They'll begin to germinate sometime in the spring.
  • If you want your Ironweed to develop additional resistance against cold, winter weather, sow your seeds in a pot. Again, be sure to plant them no deeper than 1/8th of an inch. Then, when the seedlings are two to three inches tall, move them to your garden.
  • If you prefer to sow your seeds indoors, you can do so by utilizing your refrigerator. Plant your Ironweed seeds in flats, cover them with plastic wrap, and refrigerate for about three months. When the seedlings reach at least two inches, they can be transplanted into your garden.
  • Ironweeds are large plants, so space your seeds at least 12 inches apart, no matter your method.

If you choose to grow your Ironweed from a slightly mature plant or cuttings, be sure to space the plants at least 12 inches apart. Remember: They can grow three to four feet wide, so Ironweeds need plenty of space.

Whether you choose to plant Ironweed from seeds or a plant from a nursery, it's important to choose the domesticated Ironweed—wild Ironweeds can be aggressive and crowd out your smaller, domesticated plants. Additionally, it may be illegal to remove and replant a wild plant in your area.

A close-up of New York Ironweed.
opus1ny/iStock/Getty Images 

Light

New York Ironweed plants prefer full sun, but can thrive in partial sun, too. Aim for six hours of direct sunlight or two to six hours of direct sunlight if your garden is partially shaded. If you live in a colder climate, consider planting your Ironweed in a very sunny spot with little to no wind.

Soil

Ironweeds are hardy plants, so they can adapt to many different kinds of soil. Although naturally-occurring Ironweed fares better in very moist soil, Ironweeds planted in a garden can typically survive in acidic, neutral, or alkaline soil that's dry, chalky, sandy, or high in clay.

Water

Because Ironweeds prefer medium-to-moist soil, their watering needs range from average to high. Well-draining soil or pots are ideal, but Ironweeds can tolerate low drainage, too.

Temperature and Humidity

The native area for New York Ironweed is massive, ranging from New Hampshire to Florida. Accordingly, it's a very hardy plant in terms of heat and humidity. The Ironweed grows in zones 5 (with the last frost in mid-May and the first frost in late September to early October) through zone 9 (with the final frost around the beginning of March and the first frost in mid-December).

Dividing New York Ironweed

New York Ironweed should be divided every three to four years to keep the plant healthy. To do so, carefully cut away dead parts of the crown and roots with a very sharp knife. Then, cut the leftover crowns and roots into pieces for replanting. When you replant them, be sure to leave at least 12 inches of space between each cutting.