We began in fall of 2019, with Narrowleaf Milkweed (Asclepias fascicularis) seed collected from six sites across San Diego County. That seed was planted in late 2019 / early 2020 at four different sites with support from Earth Discovery Institute, Butterfly Farms, Endangered Habitats Conservancy, and Moosa Creek. In year 2, we added Wooly Pod milkweed to the project and seeds for this and Narrowleaf Milkweed were collected from multiple sites in fall of 2020. We also sent seeds to S&S Seeds to be grown at their native seed farm. We are now in year 6 of the San Diego Native Milkweed Project, and have begun to distribute seeds and plants of local native milkweed to the public that have been grown by our partners at S&S Seed, Native West, Moosa Creek, and Anderson’s Seed Co. Special thanks to Eric Anderson of Anderson’s Seed Co. and volunteers at the San Diego Bird Alliance for preparing the individual seed packets! 

In Fall of 2021, one of our growing partners, S&S Seed Co., harvested 18lbs of Narrowleaf Milkweed seed! These seeds were originally collected from Marine Corps Base Camp Pendleton. This amount is far beyond what we expected, and we are so excited to share it with the public. If you are a backyard enthusiast looking to plant some monarch habitat, we are happy to offer a free packet of seeds. If you are working on a larger scale restoration project, we are happy to discuss larger quantities of seed.

Contact us at pollinators@rcdsandiego.org to get started!

We’re so happy that you want to grow native milkweed for monarch butterflies! This plant can take a little special care and attention to get growing, but as a perennial plant, once they are established, they return year after year. You will also be rewarded by monarch butterflies visiting throughout the spring and summer, who use milkweed as their host plant. Thank you for contributing to the conservation of monarchs and other native pollinators.

Germination Methods

• Cold Stratification: To mimic the cool winter weather, chill your seeds before planting. To cold stratify seeds, place them into a plastic bag with dampened media such as sand, perlite, vermiculite, paper towel or other media. Make sure media is moist but not too wet: it shouldn’t drip when squeezed. Seal the plastic bag and store it in a standard refrigerator for 4-6 weeks. Seeds should be sown immediately after removing from the fridge. Soil should be kept moist throughout germination period for best results. It's best to get seeds in the ground before end of June for best results. 
• Warm Water and Clipping the Seeds: This method takes more equipment and modification of the seed. It uses a warm environment to get the seeds started germinating. To heat shock the seeds, soak them in warm water for 12-24 hours, then drain and repeat this process three times. After the third warm water treatment, place the seeds in a plastic bag wrapped in a warm, damp paper towel for 24 hours before placing into moist soil.

Planting Methods

When to plant:

Milkweed seeds can be sown October through April, after cold stratifying, either in small, temporary pots, or directly into the ground or large pots.

• Sowing in a starter pot: After cold stratifying for 4-6 weeks, sew the seeds in a small container will drainage holes in early Spring. You can use a biodegradable cardboard pot to avoid having to scoop out the plant and risk disturbing roots when transplanting. Other good options are plastic yogurt containers with holes poked into the bottom. For best results, use a “seed starting mix” of soil (sometimes called a germination mix) in the top inch of soil. Wet the soil and place 1-2 seeds in the center of each pot. Cover with a fine 1/4 inch layer of soil. Gently water. A misting bottle works best to prevent pushing the seeds too far down. Place in a spot (windowsill or outdoors) that gets at least 6 hours of direct sunlight per day. Keep soil moist but not soggy during germination. Once the plant has a few sets of leaves, they are ready to be transplanted into the ground. If the plants were germinated indoors, place the potted plant in the spot where they will be transplanted for one-two weeks of hardening before transplanting. It is best to transplant milkweed in the fall (October) before the plant goes dormant. Water deeply after transplanting.
• Direct Sowing in Fall or Spring: Direct sew October through April. After cold stratifying for 4-6 weeks, plant the seeds directly into the ground in a spot with at least 6 hours of daily direct sunlight. This method takes less work, but it will be trickier to spot the seedlings as they emerge. It might allow the first roots of the seedlings to better establish themselves because you won’t disturb them by transplanting from a pot. For direct sowing, prepare the area by removing weeds and amending soil if needed. For best results, use a “seed starting mix” of soil (sometimes called a germination mix) in the top inch of soil. Seeds can then be scattered onto the soil surface by hand. After scattering, cover the seeds with a fine 1/4″ layer of soil. Gently water. A mist setting is best on hose nozzles to prevent pushing the seeds too deep in the soil. Seeds can be direct sown before rainfall in fall to early spring if temperatures are lower and the soil is kept moist.

General Care of Milkweed

Soil Type

Milkweed generally likes well-draining soil. The Narrowleaf (Asclepias fascicularis) variety can be planted in a native plant soil mix, or even a cactus mix. 

Watering

Our native milkweeds are drought tolerant so watering every 1-2 weeks is good for establishing plants but watering requirements are minimal for mature plants. Using a top mulch 4-6 inches thick is recommended to conserve moisture and reduce weed competition. Leave a 3-inch un-mulched buffer at the base of milkweed plants to prevent stem rot.

Weeding

Milkweed do not do well with competition from non-native annual plants, so it’s important to keep the area around milkweed free of weeds, especially when they are young plants becoming established, but also annually throughout their life. A 4-6 inch layer of mulch around plants (keeping a 3-inch un-mulched buffer at the base of milkweed plants) will help to prevent weed growth and retain soil moisture beneath.

Dormancy

The plants will go dormant for the winter. They may appear “dead” and this is completely normal! It is native milkweed’s smart way of keeping disease at bay and focusing nutrients on the root system. Keep the soil cool and moist over the months of December, January, and February. A 4-6” layer of mulch will help keep soil from completely drying out. If it’s a particularly dry winter, consider watering to supplement rain. At the end of February or the beginning of March the plants will reemerge from the soil, re-sprouting from the underground roots. At this time, you can begin watering the plants as normal.

Pests

You may see golden aphids on the stems of your plants. If natural predators (like lady beetles) aren’t controlling the aphid population, you can remove them by squashing them with your fingers or wetting your fingers with water and washing them off. This will need to be done regularly to keep aphid populations in check.

What if I still have non-native tropical (Asclepias curassavica) milkweed?

It’s very important that at the end of October you cut the tropical milkweed plants down to about 1 inch above the ground. This helps protect monarchs from disease and encourages them to follow natural migration patterns.

Monarch Interaction

• When to Expect Them:  You can expect to see monarchs on your milkweed plants throughout their breeding season during spring, summer, and early fall. 
• What to Expect: Monarchs rely on milkweed as their host plant; they are the only plant that adults will lay their eggs on and the only plant that caterpillars can eat. You may see an adult butterfly drinking nectar from flowers or laying their eggs on the bottom of milkweed leaves. Tiny white eggs can be visible on the underside of milkweed leaves. Caterpillars will spend about 2 weeks on milkweed, feeding and growing until they’re ready to form their chrysalis.

• Where They Go After Eating Your Plant: Once caterpillars are ready to form their chrysalis, they won’t venture too far from their host plant. Rather, they will seek out a nearby stable structure to hang from and form their chrysalis. This may be a nearby plant or branch but caterpillars might also find themselves on something like an outdoor bench, a fence, pole, or awning.

Monarch Migration 

Here in Southern California, we may encounter 2 populations of monarchs. Monarchs born in summer and late fall will migrate south to overwinter in central Mexico or along the California coast. Tens of millions of monarchs overwinter in Mexico’s forest habitats (eastern population) while hundreds of thousands monarchs overwinter in southern California (western population). See here for a map from Monarch Joint Venture showing their amazing trek!

Additional Resources

•  Milkweed Care: our leaflet on how to sow and care for milkweed seeds.
• Planting Milkweed: a quick guide on how to plant milkweed.
• Antonio Sanchez of the Santa Monica Mountains Fund made these helpful videos for sowing directly into the ground, or into pots.
• Theodory Payne Foundation's - How to Plant Milkweed 

Per the Xerces Society of Invertebrate Conservation guidance, native milkweed should only be established in areas that are 1 mile or more away from overwintering sites. You can learn more about that here. 

To see where you are in relation to an overwintering site, plug your address into this map. 

If you do live within in 1 mile of an overwintering site, you can still be a huge support to monarchs by providing native plants for nectar sources! Ideally, plants that bloom late Fall and Winter, when they are overwintering and early Spring, when they start their migration.  

CalScape Garden Planner is a great tool to design a native plant palette based on your location and bloom season. 

Happy Planting!

Earth Discovery Institute: This local San Diego organization runs a native milkweed farm in Lakeside, has an annual native plant sale, and lots of volunteer opportunities.

• Check our their "Tips of the Week" for growing milkweed and creating a thriving pollinator garden.

Monarch Joint Venture: A national partnership of federal and state agencies, non-governmental organizations, businesses, and academic programs working together to conserve the monarch butterfly migration.  

Monarch Watch: A wealth of information about monarchs – creating habitat, citizen science, migration, biology, and more. 

Xerces Society: An organization dedicated to the protection of wildlife through supporting invertebrates.  They offer information and resources about issues affecting pollinators and what you can do to help these vital insects, and their website has a section dedicated to conserving the Western Monarch.

Journey North:

• A country-wide monarch monitoring program. Report your monarch sightings and check out their interactive map of sightings so far this year!  

Xerces Society:

• Offers two citizen science opportunities. Help collect data to monitor the status of overwintering monarchs along the California coast by participating in the Western Monarch Count that takes place October - January. You can also contribute to efforts to better understand the breeding habitat of monarchs by entering your monarch and milkweed sightings through the Western Monarch Milkweed Mapper.

RCD Milkweed for Monarchs iNaturalist project:

• Join this project and contribute observations of monarchs in your gardens.

Monarch Joint Venture:

• Check out this overview of monarch citizen science programs.

Xerces Society: Milkweeds Conservation Practitioner’s Guide

 Xerces Society: Milkweed FAQs

 Xerces Society: Native Milkweed Planting and establishment in California

Xerces Society: Milkweeds Conservation Practitioner’s Guide

Monarch Watch