How to Grow New York Ironweed, a Native Plant
Every August when I see purple flowers blooming, usually around local ponds, I think to myself that those “asters” are blooming early this year. Then I look more closely and realize that they are not asters. They are New York ironweed, a native plant that blooms in August, a month ahead of the asters.
What is New York Ironweed?
New York ironweed is a perennial plant that is native to the Eastern part of the United States. In its native habitat, it is usually found growing along streambanks because it prefers moist areas. It grows in both full sun and partial shade. The plants are quite tall, 4 to 6 feet in height and can spread 3 to 4 feet. Bloomtime is August. Up close, the flowers look like they are having a bad hair day!
There are quite a few varieties of ironweed. The most popular are the New York ironweed and the giant ironweed which can grow up to 7 feet. Most people grow the New York ironweed in their gardens.
Why is it Called Ironweed?
It does seem strange that a tall green plant with purple flowers would be called “ironweed”, but if you revisit the plants in the fall after the flowers have finished and the seed heads have formed, it will become obvious. The beautiful purple flowers will have been replaced by rusty yellow seed heads resembling rusty iron. Also, the stems of the plants are very tough like iron. Both attributes are what give the plants their “ironweed” name.
How to Grow New York Ironweed
Ironweed may grow in moist areas in the wild, but it will also grow perfectly well in your garden. The tall plants make a lovely back of the border display. The ones you see for sale in nurseries and online are domesticated varieties. It’s usually not a good idea to plant wild plants in your garden. They tend to grow and spread aggressively, crowding out your tender, domesticated plants.
If 4 to 6 feet is too tall for your garden, in the late spring, you can cut back the stems. They will grow back but shorter so that the plants won’t overwhelm a small garden.
Ironweed adds interest to your garden because the flowers attract butterflies such as the American Lady, Sachem, Crossline Skipper and Fiery Skipper. If you let your plants go to seed, the birds will thank you. They love snacking on the seed heads.
The plants readily reseed themselves so be sure to remove the spent flowers in the fall. If you allow them to go to seed, you will find many new seedlings in your garden the following spring.
How to Grow New York Ironweed From Seed
Ironweed seeds need a period of cold stratification. They need to experience winter, real or fake, to germinate in the spring.
The best way to grow ironweed from seed is to sow the seeds in your garden in the fall. Plant the seeds no deeper than ⅛ inch deep. Barely cover them with soil. The seeds will germinate in the spring. Another way to start your seeds outdoors is to plant them, again ⅛ inch deep in pots that you leave outdoors so that the seeds can experience winter. They will germinate in the spring. When the seedlings are at least 2 inches tall, you can transplant them into your garden. Remember, they will grow into very large plants, so space your seedlings 12 inches apart.
You can start your seeds indoors and fool them into thinking that they have experienced winter. Most people do this by planting the seeds in flats, covering the flats with plastic to prevent them from drying out and then refrigerating the flats for a number of weeks. In the case of ironweed, it should be for 3 months. Some people go to extremes with their ironweed seeds and alternate refrigerating and freezing their seeds to really mimic winter conditions. To do this, they put their flats in the refrigerator for a day and then the freezer for a day. Then back to the refrigerator for another day followed by a day in the freezer. They keep this up for a week before removing the flats to a warm room (70⁰F) to mimic spring weather. Whichever cold stratification method you use, you can transplant your seedlings into your garden when they are at least 2 inches tall and all danger of frost has passed. Use the same 12 inch spacing as above.
Other Ways to Propagate New York Ironweed
If you don’t want to fuss with cold stratifying seeds, there are other ways to obtain ironweed plants. The easiest way is through division. Perennials should be divided every 3 to 4 years to keep them healthy. Carefully dig up your plants. Cut away any dead parts of the crown and roots, usually in the center and then cut the remaining crown and roots into pieces that you can replant. Be sure to space the plants at least 12 inches apart.
Another way to obtain ironweed plants is through cuttings. Take your cuttings in the late spring when the plant is actively growing. Cut 5 to 6 inches off an actively growing stem. Remove the leaves from the bottom 2 to 3 inches and dip that end in rooting hormone. Rooting hormone encourages the formation of roots. Place the cutting up to the level of the leaves in sterile soil. Keep the soil moist while your plant is growing its new roots. Be patient, it may take a few weeks. An easy way to tell if new roots have grown is to gently tug on your cutting. If there is some resistance, new roots are growing. If the cutting easily comes out of the soil, the roots have not yet started growing.
© 2018 Caren White