Milkweeds for Monarchs


What is milkweed and why are we growing it?

Milkweeds are a type of perennial flowering plant famous for attracting and feeding the iconic monarch butterfly species.

Native California narrow-leaf milkweed is easy to grow. It grows 2-4' tall in full sun and can handle some shade. It’s a social plant that grows best in patches. Once it’s started at a location, it’s difficult to remove. That’s why “weed” is in its name, but that's to our advantage because we want this plant to grow abundantly at Burrowing Owl Billows for both the monarch butterfly and burrowing owl.

How does planting native milkweeds save the monarch butterfly?

Monarch butterflies exclusively lay their eggs on milkweeds because their caterpillars exclusively eat the milkweeds. Milkweeds are poisonous to many others and also give the caterpillars/butterflies who consume it a poisonous/untasty affect to those who consume them, helping their species simultaneously avoid predation and have less competition for resources.

How does planting milkweeds save the burrowing owl?

The burrowing owl’s diet consists of eating bugs, including butterflies, and small rodents. Adding more native plants to their habitat creates more resources and shelter for the bugs and small rodents that the owls consume. More food for the owls means more owls!

A monarch caterpillar on our milkweed at Burrowing Owl Billows that Phil Higgins took a photo of this last April, 2022. We’ve planted 117 narrowleaf milkweed so far (55 in 2/21, 22 in 11/20, 40 in 12/2019). All were purchased at Summerwinds and transplanted, where they attract monarchs within the season.

Here's a monarch I raised indoors until it finished metamorphosing from a caterpillar into a butterfly. I released it January 11th, 2022. While raising caterpillars indoors until they're butterflies can help the monarch population by keeping them safe from predators, it is difficult to keep them fed with fresh milkweed. They eat so much of it, and the stems will wither if kept out of the fridge after harvesting for more than a couple days (even if given plant food and kept in water), I found myself harvesting stems every other day, which was destroying the milkweed plants I was taking the stems from. It's a much more effective strategy to invest in planting milkweed. Female monarch butterflies lay 300-500 eggs over two to five weeks of egg laying [source], so the issue if we want to quickly expand their numbers isn't to help them avoid predation as much as it is to help them avoid starvation.

While monarch butterflies are known to taste bad to birds, here’s a burrowing owl eating one. It is either an untasty lesson it’s about to learn or evidence of an acquired taste.

Credit: Paul Ayick/Audubon Photography Awards

Why should you avoid planting TROPICAL milkweed?

While tropical milkweed is beautiful, and more readily available and adaptable, it is detrimental to the struggling monarch population for 3 reasons:

  1. It can carry OE disease. The ophryocystis elektroscirrha (OE) is a protozoan parasite that infects butterflies that host on milkweed. Its life cycle starts as a microscopic spore that breaks open when ingested by a caterpillar. Within the caterpillar, it grows and multiplies. Because a parasite depends on its host for its own life, OE rarely kills the caterpillar, but the disease affects the development of the adult butterfly while pupating, and adults emerge weak and often with crippled wings. An adult butterfly with OE has no chance of survival when wings are malformed. [Source]

  2. It has a longer blooming season that throws off the monarchs' migration patterns. Some tropical milkweed and monarch enthusiasts will cut back their tropical milkweed to simulate dormancy.

  3. It doesn't have much of the toxin native milkweed has, so the butterflies won't taste bad/be poisonous, which will cause predators to eventually learn to ignore their markings & eat more of them.

Tropical Milkweed

Beautiful but deadly.

OE Spores

They can only be viewed under a microscope.

Malformed Monarch

This is what it does.


Our City Forest's Narrow-Leaf Milkweed Seed-Planting Instructions

Phil attended a workshop for planting California natives, organized by the nonprofit Our City Forest. Here's his report back about their instructions for planting narrow-leaf milkweed seeds:

They placed them in a paper bag or glass jar that was sealed, and left them in the fridge for about two months before planting them. This is to simulate a cold winter period.

They used a potting mix of half potting compost and half perlite. They put both items into a basin and watered it until it could be lifted up and formed a ball, so as not to over saturate but enough to keep sufficient moisture.

They then placed the mix into pots and placed 3 seeds in each pot. They place them in a glasshouse and they have an automatic mister water them four times per day for approximately 60 seconds each time. Again, they do not recommend saturating the seeds but keeping them moist.

I asked about growing milkweed seeds at home without a glasshouse. They recommended placing a plastic container over the pot to simulate a glass house and maintain a moist environment and watering them with a spray bottle at least 4 times per day.

If all three seeds germinate they remove 2 of them so one will be healthier.

This was a nursery preparing plants for purchase, so they are probably more inclined to make sure everything looks nice and neat. I have seen other instances where they remove extra seedlings to ensure the healthiest individual survives. Also, this is just one person’s personal seed preparation method, I am sure if you went to several classes on seed preparation they would all vary somewhat.

It's best to try different methods to see what works, then I presume potting, compost, watering schedule, and exposure to light will all have an impact, so what works for one volunteer may not work as well for someone else.

The above instructions are good to read through if you haven't already started planting your seeds yet because these are local experts in our area professionally conducting a workshop, however, the below instructions are based on consolidating the instructions from multiple sources, both in person and online. I invite you to experiment to try what you think might work best given your environment and resources. Please report back so by the time we transplant our first plants we can consolidate and improve these instructions for what's most effective for our project and purposes.

Optional Cold Stratification

Exposing your seeds to the cold before planting them can help to stimulate the growth cycle by simulating cold winter weather. To do this, put your seeds on a wet paper towel, in a plastic bag, and in the fridge for 1 month. This step is "recommended but optional." As this is the first time we're trying this project, please experiment (you could try some seed with cold stratification and some without) and report back with your results.

[Source: for the below photographs and steps]
  1. Sprinkle Seeds on Wet Paper Towel

Wet a paper towel and gently wring it out so it is damp but not dripping with water. Too much water may cause the seeds to mold inside the bag.

2. Fold Paper Towel into Quarters

Sprinkle the seeds onto half of the paper towel first so the seeds will not overlap when you fold it.

3. Place into Ziplock and Fridge

Label the bag with the date and type of seed. Set a reminder on your phone or calendar so you can remember to take them out in 30 days.

Planting Seeds and Caring for Plants

  1. Make sure you have enough outdoor space in full sun for all your 1-gallon containers. Your containers will stay in this location throughout until we transplant them at Burrowing Owl Billows.

  2. Fill 1-gallons with DAMP soil to 0.5 inches below rim. Mix soil with water before or while filling containers to create DAMP soil.

  3. Create 3 holes with your finger ⅛-¼ inches deep, spaced 2 inches apart in a triangle at the center of your 1-gallon container.

  4. Drop 5 seeds per hole.

  5. Lightly cover holes with soil (not more than ⅛-¼ inches).

  6. Press soil over seeds so it’s gently packed. Do not leave any of seed exposed to air.

  7. Spray-water once a day, everyday. Do not let soil dry out, but also do not overwater. The goal is to keep seeds MOIST until germination, but NOT DRENCHED.

  8. Expect to see sprouts in 7-10 days.

  9. After you see sprouts, focus on watering deep (to get to the roots) and less on the surface (don’t use a spray bottle anymore). Water every 2-3 days in full sun. Tip: You can determine how much water your gallon needs by weight. If it’s too light, you need to water. If it’s already as heavy as it was the last time you watered, skip watering this time and check again later.

  10. If sprouts do not rise from all 3 holes within 7-10 days, seeds can be re-added to the vacant spots to try again.

  11. Expect milkweed to grow up to ~6-inches above surface in the fall. Then the top-growth will “die-off” over the winter, but the root-ball will remain. This is called “going dormant." Keep watering lightly. Beginning in the spring, the top-growth will return and this will be when we transplant.

Gail picked up and purchased our seeds from Larner Seeds for our first round of this project! Thanks, Gail!


The instructions above were created by referencing the following:


Reach out to me ( if you have any questions or feedback on the instructions. Please also keep Gail and I informed about how your seeds/plants are doing so we can hone the instructions to optimize for better seed-to-plant-to-transplant success.

This project is part of The Guardian Project: Save the Burrowing Owl.