Milkweed and Monarchs 

Monarch butterflies have been in sharp decline since the 1990s due to the loss of milkweed (Monarch caterpillars eat only milkweed), pesticides, changing weather patterns, and overwintering habitat loss. 

Good news! The World Wildlife Foundation Mexico reported in January 2019 that the monarch population has nearly doubled from last year. While this is exciting news, experts know that one count in one year doesn’t mean our work is done. Monarchs have lost 165 million acres of breeding habitat in the U.S. alone, so there is still more work to do to keep them from being considered endangered.

Home gardeners can help, too!

  • Sow milkweed that is native to your area.
  • Sow native plants in the landscape to supply quality food for other pollinators.
  • Don’t use pesticides, rather, look for garden pests regularly, dispose of them, and build a habitat that invites predatory insects.
  • Become a citizen scientist and share your observations, helping scientists get a fuller picture of the monarch population.

Milkweed: Sow and Grow Guide

Milkweed: Sow and Grow Guide

Not only is milkweed a beautiful addition to the garden, but it is the only food monarch butterfly caterpillars can eat (what is called a “host plant”). For many years, milkweed has been sprayed with herbicides and eradicated from farms, yards, and public landscapes because, although native, was undesirable in those areas, and its ecological importance was not recognized. This reduction in milkweed has been linked to the drop in the monarch population, which has declined 90% in the last 20 years. Growing milkweed in your home landscape can help save the monarch butterfly population; and it’s fairly easy to grow, as milkweed is virtually care-free once established and provides wonderful summer blooms that other pollinators flock to, also.


When to sow outside: 2 to 4 weeks before your average last frost date, or fall for spring germination.

When to start inside: 6 to 8 weeks before your average last frost date.

Special sowing instructions: Stratification aids germination. Stratification is the process of subjecting seed to moist, cold treatment to break dormancy, which occurs naturally when seed is sown outdoors in fall. To mimic this process when starting seed indoors in spring, sow the seed into a resealable bag or in a growing container of moistened seed-starting mix, cover with clear plastic wrap, and leave the container in a refrigerator for 3 to 6 weeks, checking moisture occasionally. Then move to a warm location to germinate. 


Sowing preparation and spacing

With exception to Irresistible Blend Milkweed (i.e., Swamp Milkweed), which does best in moist, even muddy clay conditions, the other milkweeds we carry are drought tolerant and need well-drained soil. You can improve your soil’s drainage by mounding soil, adding organic material, or planting in a berm.


Water frequently to establish; however, once established, water only when soil becomes dry, as plant has a large tuberous root and can withstand drought. Irresistible Blend/Swamp Milkweed thrives in average to wet conditions.


Not necessary.


Keep area well weeded.


When 3″ tall, thin to 12″-36″ apart, depending on the variety.

Asclepias tuberosa thin to 1 every 12″-24″

Asclepias syriaca thin to 1 every 12″

Asclepias incarnata thin to 1 every 16″-36″

Asclepias speciose thin to 1 every 12″-16″


Transplant seedlings after hardening them off, around your average last frost date. Once this plant becomes established, it is difficult to transplant because of its deep taproot. Plant it where it will not be disturbed. Milkweed spreads readily through underground rhizomes, so plant in your garden where expanding growth is desired, growth can be controlled, or in containers.

Special care

Deadheading flower clusters before pods set will prolong the flowering period and prevent reseeding. Avoid spraying plants with any pesticides that could harm or deter monarch butterflies.

Choose Your Region

By sowing milkweed that is native to your region, blooming will occur when most needed–at the time of migration in your area–providing fuel for these beautiful butterflies.

*Botanical Interests