When is the Best Time to Plant Milkweed Seeds in Idaho?

Planting milkweed seeds in Idaho can be a beneficial way to attract wildlife, especially Monarch butterflies, to your yard. While purchasing full-grown milkweed plants from a garden center can be expensive, growing them from seeds is a more affordable option. Contrary to popular belief, the best time to plant milkweed seeds in Idaho is actually in the fall. This is because milkweed is native to Idaho and has adapted to thrive in cooler temperatures. The cold weather in winter provides the necessary freezing and thawing temperatures, combined with moisture, for the seeds to germinate in spring. Planting milkweed seeds in the fall ensures that they have enough time to go through this process and start growing in the spring. Additionally, if you want to start your seeds indoors in the spring, they must undergo a process called artificial stratification, which simulates the effects of winter. Overall, planting milkweed seeds in Idaho can be a rewarding experience that benefits both wildlife and your yard’s aesthetics.

When is the Best Time to Plant Milkweed Seeds in Idaho?


In Idaho, planting milkweed seeds is an excellent way to support local wildlife, particularly Monarch butterflies. Milkweed is the only plant that Monarch caterpillars will eat, making it crucial for their survival. Growing milkweed from seeds is an affordable and rewarding option for gardeners. However, knowing the best time to plant these seeds can be a bit perplexing. This article will explore the ideal time to plant milkweed seeds in Idaho, as well as factors to consider, growing techniques, and caring for the plants after planting.

The Importance of Milkweed

Milkweed is a native plant in Idaho and plays a vital role in supporting local wildlife. It offers numerous benefits for both insects and birds. For instance, milkweed provides nectar for bees, butterflies, and other pollinators. Additionally, many insects rely on milkweed as a host plant, where they lay their eggs and the resulting caterpillars feed on the leaves. This makes milkweed an essential plant for supporting insect populations and the larger ecosystem.

One particular species that depends on milkweed is the Monarch butterfly. Monarchs are famous for their long-distance migrations, and their caterpillars exclusively eat milkweed leaves. Without milkweed, the Monarch population would suffer greatly, highlighting the critical role this plant plays in their lifecycle. Therefore, planting milkweed in Idaho is not only beautiful but also necessary for wildlife conservation efforts.

Growing Milkweed from Seeds

Growing milkweed from seeds is an economical way to introduce this beneficial plant to your garden. Buying fully-grown milkweed plants from a garden center can be costly, making seed germination a more viable option. When planting milkweed seeds, it’s important to understand the best time to sow them and the necessary growing conditions for successful germination. Let’s dive into the specifics of planting milkweed seeds in Idaho.

The Best Time to Plant Milkweed Seeds in Idaho

The surprising answer to when to plant milkweed seeds in Idaho is the fall. Unlike many other plants that are typically started indoors during the spring, milkweed is native to Idaho and has evolved to thrive in cooler temperatures. Planting milkweed seeds in the fall allows them to undergo natural stratification, a process that prepares the seeds for germination. The freezing and thawing temperatures of winter, along with moisture, help break the seeds’ dormancy and promote successful germination in the spring.

Factors to Consider When Planting Milkweed Seeds

When planning to plant milkweed seeds, several factors should be considered to ensure their successful growth. These include:

Choosing the Right Milkweed Species

There are several milkweed species that grow well in Idaho, including Asclepias speciosa, Asclepias incarnata, Asclepias tuberosa, and Asclepias fascicularis. Researching each species’ specific requirements and growth habits can help you select the most suitable type for your garden.

Sunlight and Soil Requirements

Most milkweed species thrive in sunny areas with well-drained soil. Ensure that the location you choose for planting milkweed receives at least six hours of direct sunlight per day. The soil should be fertile and well-drained to prevent waterlogging, as excessive moisture can cause root rot.

Climate Considerations

Idaho’s climate varies across different regions, so it’s essential to choose milkweed species that are well-adapted to your specific area. Consider the average frost dates in your region to determine the optimal time for planting milkweed seeds.

Choosing the Right Location for Milkweed

Once you’ve selected the appropriate milkweed species for your garden, choosing the right location is crucial. Milkweed plants require ample sunlight to grow and thrive, so select an area that receives at least six hours of direct sunlight each day. Additionally, ensure that the soil in the chosen location is well-drained to prevent waterlogging. When planting multiple milkweed plants, give them enough space to grow comfortably without overcrowding.

Preparing the Soil for Planting Milkweed Seeds

Preparing the soil before planting milkweed seeds is essential for their successful germination and growth. Begin by clearing the area of any weeds or vegetation to reduce competition for nutrients. Loosen the soil using a garden fork or tiller to create a loose, crumbly texture. This will help the roots penetrate the soil easily. Incorporating organic matter, such as compost or well-rotted manure, can improve soil fertility and drainage.

Planting Milkweed Seeds in the Ground

Proper planting techniques can significantly impact the success of your milkweed seeds’ germination and growth. Follow these steps to ensure optimum results:

  1. Determine the recommended planting depth for your specific milkweed species. Generally, milkweed seeds should be planted about the length of your fingernail deep.
  2. Create small holes in the prepared soil at the recommended planting distance, typically around 1-2 feet apart, depending on the species.
  3. Place one seed in each hole and cover it with soil, gently patting it down. Avoid burying the seeds too deeply, as they need light to germinate.
  4. Water the newly planted seeds thoroughly to provide moisture for germination. Ensure that the soil remains consistently moist but not waterlogged.

Caring for Milkweed After Planting

After planting your milkweed seeds, it’s essential to provide proper care to ensure their healthy growth. Regular watering is crucial, particularly during dry periods. Keep the soil consistently moist, but avoid overwatering, as it can lead to root rot. Additionally, monitor the plants for any signs of pests or diseases and take appropriate measures to prevent or treat them.

Starting Milkweed Seeds Indoors

If you prefer to start your milkweed seeds indoors in the spring, it is still possible, although it requires additional preparation. The seeds must undergo a process called artificial stratification, which simulates the effects of winter. Place the milkweed seeds in a moist paper towel and store them in the refrigerator for a few weeks. This cold treatment will break their dormancy and prepare them for germination.

Artificial Stratification for Milkweed Seeds

To perform artificial stratification on milkweed seeds, follow these steps:

  1. Moisten a paper towel, ensuring it is damp but not soaking wet.
  2. Place the milkweed seeds on one half of the paper towel, spacing them out to avoid overcrowding.
  3. Fold the paper towel over the seeds to cover them completely.
  4. Place the paper towel with the seeds in a plastic bag and seal it.
  5. Store the bag in the refrigerator for 4-6 weeks, maintaining a constant temperature between 35-40 degrees Fahrenheit.
  6. After the stratification period, remove the seeds from the refrigerator and proceed with the indoor sowing process.

Transplanting Milkweed Seedlings Outside

When the weather has warmed, and all frost dangers have passed, transplant your indoor-sprouted milkweed seedlings outside. This usually occurs 4 to 8 weeks before the anticipated last frost date in your region. Ensure that the soil has warmed up sufficiently before transplanting to prevent shock or damage to the young plants. Gradually acclimate the seedlings to outdoor conditions by placing them outside for short periods at first and gradually increasing their exposure over several days.


Planting milkweed seeds in Idaho is an excellent way to support local wildlife and create a beautiful garden. The best time to plant milkweed seeds in fall, allowing them to undergo natural stratification and germinate successfully in the spring. It’s important to consider factors like milkweed species, sunlight, soil conditions, and climate when planning to plant milkweed. By following proper planting techniques and providing adequate care, you can enjoy the vibrant, blooming milkweed plants while helping to preserve Idaho’s wildlife population.

Nature Blog Network

NatureBlogNetwork.com is the leading birding research and information website. Serving the birding community since 2010.

Recent Posts