New York Ironweed – Facts, Identification, Growing Info


NY Ironweed

New York Ironweed is a herbaceous perennial wildflower with dark purple-to-pink blooms native to Eastern North America.  Blooming in late summer to early fall, this tall plant will draw in the butterflies with its tubular flowers.  I often see this plant growing in ditches and along roadsides.  But you can also find it in open woods, clearings, anywhere moist that gets at least partial sun.

 Ironweed Facts

Physical Description

This is a tall, erect herbaceous perennial flower that is typically around 5-6′ tall (1.5-1.8 m), but can range from 4-8′ depending on conditions.  It generally can stay vertical and will not flop over, which is a nice benefit in a garden.

Stalk / Stem

The stalk is stiff and green, normally reaching heights of 5-6′.  There will not be any branches until the last 6″-12″ of stalk, where it will make branches into a panicle to produce flowers.

Leaves

The leaves are large, from 3-12″ long.  Leaves of NY Ironweed are generally lance-shaped to oblong / oval, almost resembling a spear tip.   They are alternate along the stalk.

Flower

There will be many flowers heads along the panicle at the top of the plant.  The size of the flat-top cluster of flowers is roughly 6″-12″ (15-30 cm).  There will be numerous small purple-to-reddish purple, or even pink colored blooms.

Root

This plant has short rhizome roots and fibrous roots.  Small colonies are formed through the short rhizomes, but it isn’t too aggressive.

Growing Conditions

New York Ironweed will grow well in full sun to partial shade.  I’ve observed it in both conditions, as they grow in the ditches, and the available sunlight seems to have a large effect on the final height.  In general though, this plant likes moist to medium moisture soil.  As far as soil types, it can grow well in loam and clay (yes, clay).  It may have trouble in sandy soil if it drains too much.  However, I have seen this plant to just fine in drought conditions, as roadside ditches experience drought the same as anywhere else.

Some New York Ironweed (left) growing in a ditch along a road. With an abandoned farm field in the background. This plant was mowed in July, and is only a couple of feet tall.  New England Aster is on the right.

How to care  for

As with most plants, the best way to care for them is to plant them in their preferred growing conditions!  Give it partial-full sun (4-6 hrs per day), and moist spot in the garden and it should do just fine.

Maintenance

Vernonia noveboracensis

You can cut the plant back in Spring after insects have emerged from dormancy.  But other than that, no maintenance is really required.  If you feel that your plants grow too tall, you can cut them back in late Spring to reduce the final height.

How to Establish New York Ironweed

Plant Ironweed seedlings in the early Spring or Late Fall before the ground is frozen.  In that way, the roots will have plenty of time to get established while there is little water demand from the plant.  This is because the cooler temperatures allow the plants to grow without using water to cool themselves.

How to Grow Iron Weed from Seed

Ironweed is somewhat difficult to establish from seed.  The trouble is, the seed from Ironweed may need to be refrigerated to stay viable.  Furthermore, I think fresh seed must be sown, and you cannot store it year to year.

ironweed seedhead seeds
Green seed heads from iron weed. The seed resembles small twigs.

So, you collect some seed – dry it, then refrigerate it in a sealed container.  Then finally you can stratify it for probably 2-3 months, or just winter-sow it.  I generally plant it anywhere from 0-6 mm.  I’ve found that most of the seed doesn’t seem to be viable when starting in pots, as my germination rate has been very low.

Ironweed Seedling
1st year Ironweed seedlings.

The best success I’ve had with this plant was direct sowing in fall, right after seed collection.  I got approximately 5-6 plants to grow to seedling form, and a couple even bloomed the first year.  But the time to germination was loooong.

UPDATE (APR 2020) for Germinating Ironweed Seeds!

Ironweed Seedlings, after several long years of trying!

I have figured it out!  I used to following process to get a decent number of seeds to germinate!  Finally!  Ok, so my new updated process for germinating Ironweed is as follows;

  1. Gather Wild Seed.  Gather seed from the wild, or a known population if you can.  I found that getting YOUR hands on fresh seed seems to be very important.  I think the shorter the time from harvest to storage, or sowing the better.
  2. Store in sealed container in fridge.  Store the seeds in the refrigerator in a zip-lock bag or plastic container until you are ready to plant (at least by January).  Make sure you get them stored right away after collecting them!  I have a strong suspicion that if they dry out, most seeds may lose their viability.
  3. Winter-Sow / Plant seeds.  Plant the seeds just under the soil surface, and just on top!  I know, why both?  Since I’ve never had much luck planting seeds 1/4″ deep, I figured why not try shallower?  So, I placed about 5 seeds per cell, then covered with ~1/8″ of soil (3 mm).  Then, I scattered and pressed in some more seed.  I did this in January, then it was time to put the seeds out for winter sowing.
  4. Keep moist .  During the winter you may need to water a couple of times.  If the temperature is far below freezing, then don’t worry about it.  But just try to maintain a bit of moisture in the soil around the seed.
  5. Place Winter Sow container in the correct location!  When temperatures begin to warm up (50F high temp), place in morning sun/afternoon shade location.  I’ve found this to be critical with some native perennials.  I’ve found that placing my seed flats or jugs so they get hit by the sun for at least a few hours in the morning (early March) gives the best success.  And by best success, it isn’t even close.  I have gotten the highest germination rates this year for all seed types, not just Ironweed.
  6. Have Patience.  I found that Ironweed (and Joe-Pye) germinated much later than most other species that I grew this year.  While Fall Phlox germinated in really cold temperature, Ironweed needed consistently warmer temps before germinating.  Just my observation.
Ironweed Seedlings in small pots
Large New York Ironweed seedlings ready for transplant out into the garden!

Ironweed Garden Uses

This plant can be excellent at the back of a well manicured flowerbed.  Its tall and erect stature will provide a late summer / early fall wall of purple blooms that is long lasting.   Also, Ironweed is a perfect plant for a rain garden.  It loves moisture (but not flooding), and does great in partial shade.  Just make sure it doesn’t block the view of other plants.  So, put it in the back, or as a central focal point to walk around.

This plant is approximately 4′ tall, and is facing East. So it probably gets less than 6 hours of sun per day in the summer.

It can be an integral part of a moist micro prairie, or even in just a ‘moist part’ of one.  We grew about 5 seedlings this year from direct sowing in the previous fall.  We were even treated to a single bloom!  I think a certain herbivore species decided they needed to trim these off for us (more on that later).

Side note – click below to see how to make your own backyard Micro-prairie!

Companion Plants

New York Ironweed would grow well with other moisture loving, partial shade to full sun plants.  Placing a layered flower bed with Ironweed in the back, Swamp Milkweed in front, and Blue Lobelia in front of that would be striking from July through September.  Adding in some Virginia Bluebells would further provide color for almost the whole year.

Fauna

This plant is a host to numerous moth caterpillars.  The foliage is also eaten by other insects and aphids.  Flowers are beloved by bees, butterflies, and skippers.

Pests and diseases

Ironweed generally does not get diseases.

For deer/rabbits, most references you will find list this plant as being deer resistant.  In my experience, deer will browse this plant.  It was quite frustrating, but I lost the tops of plants (where the flowers were), and I assume they were deer.  I don’t think it was rabbit damage, as they generally consume the whole plant, or just snip off the top and leave it laying beside the plant.

NY Ironweed Reference Table

Common NameNew York Ironweed
Scientific nameVernonia noveboracensis
Bloom TimeLate Summer / Early Fall
Bloom DurationApproximately six weeks
ColorDark Purple to Pink
Bloom SizeCluster of small flowers 6-12” diameter (15-30 cm)
CharacteristicsA cluster of small individual flowers, on small branches forming a panicle
Height4-8’
Spacing/Spread3’ spread (1 m)
Light RequirementsFull Sun / Partial Shade
Soil TypesClay, Loam
MoistureMoist to Medium
MaintenanceNone.  Cut back in Spring after insects have emerged
Typical UseMeadow, prairie, roadside
Fauna AssociationsCaterpillars and other insects feed on foliage
Larval HostNumerous moths
Sowing Depth0-1/8” (0-3 mm)
Stratification60 days cold stratification.  Or direct sow in Autumn/Winter – You need fresh seed!
Native RangeUSDA Zones 5-9
NotesGrowitbuildit.com

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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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