Along with other species in the Vernonia genus, New York ironwood holds appeal to gardeners who prefer native plants. Growing up to 7 feet tall, this member of the aster family is popular in wildflower gardens, where during the growing season butterflies, bees, and other pollinators flock to it for its nectar. Out of season, the New York ironweed’s tall, dead stalks provide sturdy perches for migrant birds. New York ironweed is a fast-growing, fast-spreading plant that is normally planted in the spring from potted nursery starts or in the fall from direct-sown seeds. Even when grown from seeds, it sometimes blooms in its first summer season. New York ironweed is such a dramatic plant that you might be tempted to dig up and adopt wild plants you find on public lands or along roadsides to transplant into your own garden. But if this plant is growing wild in your region, it’s possible that you will find it to be overly aggressive in your garden. And in some regions, it may be illegal to remove and replant any wild plant species.
Light
New York ironweed plants prefer full sun, but can thrive in partial sun, too. This plant needs at least four hours of direct sunlight each day, but six to eight hours is better. If you live in a colder climate, the plant will prefer as much sun as possible.
Soil
Ironweeds are hardy plants, so they can adapt to many different kinds of soil, though they will naturally thrive in moist, loamy soil that is somewhat acidic in pH. Extremely barren, dry soil is the only environment where this plant is likely to perish.
Water
Because ironweed prefers moist soil, it will need at least 1 inch of water per week, and will readily tolerate even more. It will also do quite well in boggy, poorly draining soils where many other plants struggle.
Temperature and Humidity
New York ironweed readily tolerates the heat and humidity patterns throughout its hardiness range, zones 5 to 9. Where the climate is naturally arid, it may require more ground watering.
Types of Ironweed
In addition to New York ironweed, there are several other species in the Vernonia genus, and some of them are even more popular than New York ironweed as garden plants, especially for colder climates. Some other ironweed species you should consider:
Vernonia gigantea ‘Jonesburo Giant’ grows to as much as 12 feet tall and 5 feet wide. Deep purple flower clusters appear in autumn. It is hardy in zones 5 to 8.V. angustifolia ‘Plum Peachy’ is a 42-inch-tall blue-violet variety that is hardy in zones 7 to 9.Vernonia lettermannii or “Iron Butterfly” has deep purple flowers on short, 3-foot-tall plants. This summer bloomer is hardy in zones 4 to 9.Vernonia or “Summer’s Surrender” is a hybrid cross of V. lettermannii and V. arkansana. It has violet flowers on 4-foot plants and is hardy in zones 4 to 9.Vernonia or “Summer’s Swan Song” is a hybrid created by crossing V. lettermannii and V. angustifolia “Plum Peachy.” It has violet flowers on 3- to 4-foot plants and is hardy in zones 4 to 9.
Pruning
New York ironweed requires no pruning, but deadheading spent flowers is a good idea if you want to limit its self-seeding habit, which can cause the plant to spread invasively. At the end of the growing season, garden plants can be cut down to near ground level.
Propagating New York Ironweed
New York ironweed should be divided every three to four years to keep the plant healthy and to create new plants to share. Here’s how to do it:
How to Grow New York Ironweed From Seed
New York ironweed is fairly easy to grow from seeds, either by direct sowing in the garden or starting seeds indoors. For outdoor direct-seeding, plant the seeds in the desired location, about 1/8 inch deep. Leave them to overwinter, and the seeds will germinate and sprout in the spring. If starting seeds indoors, they will need a period of cold stratification. Plant them 1/8 inch deep in flats or pots filled with commercial potting mix, cover them with plastic, and refrigerate for about three months. At this time, take the pots out and uncover them, then place them in a warm, bright location until the seeds sprout. When the seedlings are at least 2 inches tall, they can be transplanted into the garden after a hardening off period.
Potting and Repotting
Perennial wildflowers such as New York ironweed are not commonly grown in container culture, but should you want to try it, any well-draining container filled with a general-purpose potting mix will work. Potted plants will need more frequent watering. Remember that perennials grown in containers may need some shelter in the winter, as the roots are more exposed to cold than they are when growing in the ground.
Overwintering
These hardy plants need no special winter protection. Some gardeners like to cut off the dead stalks to just above ground level as winter sets in, but others like to leave the stalks and dried flower head intact to serve as resting/feeding perches for winter birds.
How to Get New York Ironweed to Bloom
This plant rarely withholds its flowers, which generally appear from midsummer well into fall. If a plant does not bloom, it’s possible that it is not getting enough sun. If a clump begins to bloom less vigorously, it may be a sign that the plant needs to be dug up, divided, and replanted in order to rejuvenate it. It’s not uncommon for newly planted specimens to bloom weakly, or not at all, in their first year, especially if soil conditions are less than ideal. Be patient; by the second year, they should bloom vigorously.
Common Problems With New York Ironweed
New York ironweed does not elicit many complaints from gardeners who appreciate native plants and wildflowers. You may observe a couple of issues, however:
Plant Is Spreading Too Rapidly
A New York ironweed plant that spreads quickly, to the point of invasiveness, is announcing that it very much likes the conditions in which you’ve planted it. This can often occur where ironweed is growing in boggy areas that are constantly moist. You may need to remove the plant entirely if this behavior is a problem or be prepared to dig out the expanding roots frequently.
Plants Are Unusually Short
If your New York ironweed plant is considerably shorter than the 7-plus feet that is normally expected, it is probably because it is soil that is too dry. Increasing the watering volume and intervals may prompt taller growth. It’s also possible you have mistakenly planted another of the species in the Vernonia genus. There are other native species of ironweed that grow only to 3 or 4 feet in height. Ironweed looks especially natural and complementary when planted with other fall composite flowers, such as Joe-Pye weed, goldenrod, or bright yellow sunflower species. If you’re concerned with deer damaging your garden, ironweed plants make an excellent choice because they are rarely browsed.
