Milkweed 101

Native Milkweed for Iowa

Iowa is home to 18 different native milkweed species! Although we often just think about common milkweed and pink flowers, milkweeds come in a variety of shapes, colors, and growth habits. Below are some of the most popular milkweed species to establish in prairies and gardens. 

Milkweeds for Prairies

When it comes to large prairie establishments, any native milkweed species will work well. Selecting a species will depend on the soil conditions as certain milkweed species may do better in specific soils types over others. The native milkweed species most often found in reconstructed prairies is common milkweed, although butterfly milkweed and other species are often used in restoration efforts and along roadside plantings. Whichever species are most readily available will work well. Combining native milkweed with a variety of native nectar plants that bloom early spring to late fall will create high quality monarch habitat.

Milkweeds for Pollinator Gardens

Native milkweed species with a shorter growing height that don't spread as much tend to work best for pollinator gardens. For wetter areas, like rain gardens, swamp milkweed is a great choice. Butterfly milkweed is another good option for pollinator gardens with its vibrant orange flowers. For larger garden areas, whorled milkweed or prairie milkweed can work well, although these species are known to spread a bit which is why they need a larger planting area. For shaded sections of your garden, try poke milkweed. Though this species does grow rather taller, it can be a good background plant for shadier areas. Avoid selecting species that spread aggressively, like common milkweed, as these species can be more difficult to manage in smaller gardens.

To start, plant a minimum of 2-3 native milkweed plants in your garden. If you have the space, adding in multiple species of native milkweed will enhance the area. This, along with a variety of native nectar plants blooming early spring through late fall, will provide good habitat for monarchs.

Purchasing Milkweed

When purchasing milkweed plants, it’s important to ensure that they haven’t been treated with pesticides. Pesticides can have a negative impact on pollinators and the plants they rely on, so make sure to check with the nursery and ask if pesticides have been used on the plants. Additionally, make sure to only purchase and plant native milkweed species. Non-native milkweeds like tropical milkweed (Asclepias curassavica) or balloon milkweed (Gomphocarpus physocarpus) can increase the spread of disease among monarchs and disrupt their migratory journey. If you have any non-native milkweed in your garden, try swapping it out for native species instead.

Where to Buy

Always try to purchase native milkweeds locally. This will help maintain genetic diversity across milkweed populations and ensure that plants are adapted to your local soil and climate. Milkweed can be purchased as seeds, plants, or rhizomes (root segments) depending on your budget and planting needs. A few sources for purchasing milkweeds are listed below. You can also check with your local gardens, parks, and County Conservation Boards as they will often host native plants sales in the spring.

• Tallgrass Prairie Center
  • Offers a list of local seed vendors as well as those that sell plants
• Monarch Watch Milkweed Market
  • Opens for pre-orders in January
• Monarch Joint Venture
  • Offers native plant kits for the Midwest and Eastern US
  • Also has a map of milkweed and wildflower vendors for Iowa and the US
• Blank Park Zoo
  • Provides list of vendors that sell seeds and plants
• Xerces Society
  • Includes a map of milkweed vendors across Iowa and the broader United States

Seeds vs Plants vs Rhizomes

When it comes to choosing between purchasing seeds, plants (plugs), or rhizomes, it really depends your budget, size of planting, and time availability. Seeds are often the least expensive, are easy to disperse, and are ideal for large habitat projects. However, they do have the lowest establishment rates, and you have less control about the placement of specific plants. Rhizomes are also a good option for larger restoration efforts, have the highest survival rates, and are quick to plant. That being said, they are the most expensive option and are not always available to purchase. Plants are often the middle ground; they are usually more expensive than seeds but cheaper than rhizomes. They also have a higher survival rate compared to seeds but lower than rhizomes. Plants are a good option for smaller areas, like pollinator gardens. They will require a larger time commitment to help them become established, but they do allow you to design a specific layout and control where plants become established. Monarch Joint Venture provides a good overview of how to plant milkweed plants and seeds. Some of the main points are summarized below.

• Seeds
  • Seeds are best planted during the dormant season (mid-November through March) allowing the seeds to stratify during the cold winter temperatures which increases germination success. Seeds can be hand-sown through broadcasting or drilled into the ground. The spring snowmelt will help seeds establish.
• Plants
  • Plants can be placed in the ground after the last frost date (mid-May). Dig a hole slightly bigger than the size of the pot and place the unpotted plant inside so that it is level with the ground. Make sure that the plant isn’t planted too shallow where the roots are exposed or too deep where the stem is buried. Water the plants daily for the first two weeks and then gradually shift to less frequent waterings. To help retain soil moisture and deter weed growth, add a layer of mulch around your plantings. After a few months, your plants should be established and no longer require supplemental irrigation unless there is an extended drought.
• Rhizomes
  • Rhizomes should be planted during the fall or early winter before the ground freezes. Rhizomes can be planted in shallow holes 2-6 inches below the surface. Spring snowmelts will water in the rhizomes and help them establish.

Common Milkweed Visitors 

Monarchs aren’t the only species that utilize milkweed. Insects, like the Milkweed Tussock Moth, utilize milkweed as a host plant for their caterpillars. Others, like Milkweed Bugs and Milkweed Beetles, feed on the leaves of milkweed plants. These insects pose no threat to monarchs and can coexist on milkweed plants to the benefit of both.

Many pollinators will also use milkweed flowers for gathering nectar and pollen. Bumble bees, along with many other species of native bees and butterflies, are often found visiting milkweed plants in bloom. By creating monarch habitats filled with a variety of native plants, you are also providing habitats for many other native pollinators which can in turn support birds and other wildlife.