By Jordan Isken, Production Manager
At the winter plant sale this last weekend, one of the most frequent requests from customers was for milkweed plants. The most common species that we grow at TPF, in order of popularity, are narrow-leaf milkweed (Asclepias fascicularis), showy milkweed (A. speciosa), and Kotolo milkweed (A. eriocarpa). All three are essential habitat plants for the western population of the beloved monarch butterfly, and their seasonal winter dormancy is an important cue for the monarchs to stop laying eggs and migrate to an overwintering spot along the coast. In the garden, these milkweeds are not only appreciated as a host to butterflies and insects alike, but they also provide greenery and flowers deep into the heat of the summer before retreating underground again in the fall. Milkweeds apparently love the heat, as the plants do not reemerge until the warmer months of late spring, and the seeds do not germinate until this time either. Due to this winter dormancy, we are unable to sell plants until they have come out of dormancy and, due to germination cues, we must wait to sow the seed.
Alas, it is impossible for TPF to offer California native milkweed plants at this time of year. But I hate to have unsatisfied customers, so below I have detailed exactly how we grow milkweed seed, so that you might be able to start your own this year from
home (with seed purchased from our shop!).
As a grower, I must admit that milkweed is one of the easiest plants that we grow…by far. Its predictable and uniform germination makes it an excellent candidate for first-time seed sowers. The first, CRITICAL step is to wait until we get warmer temperatures. At the earliest, you can sow the seed in March, but germination can be achieved all the way into July (sowing any later than July is risky, as the plant needs to be robust when going into dormancy).
Here at TPF, we sow the seeds into small plug trays, but any container (preferably one gallon or smaller) will work. Start by filling your container with any seed-starting or high-drainage potting medium (typically cactus mixes or anything with added perlite, including TPF’s own custom mix). Dig a small hole about 1/2 inch deep and place anywhere from 2 to 4 seeds and lightly bury. After the seed is sown, give the pot a good soak and make sure to wet the medium entirely. Place your container outdoors in full sun. Allow the surface to dry down before watering again, but keep in mind that your seed is in the top inch of the soil that needs to stay moist, so don’t let it dry down too much. Your watering schedule will likely be every 2 to 3 days. Once the seeds have emerged, they will begin to drink up the water and watering will be more frequent, particularly after the plant starts putting on growth and begins to fill .the pot with roots. If multiple individuals germinate in your pot, you can thin or leave them clustered. Milkweed seedlings don’t seem to mind growing in
Another option is to sow the seed directly into the ground. The instructions above are roughly the same for in-ground germination. You want to find a spot in a sunny location that is not competing with nearby plants (at least until your seedlings are established). Lightly bury the seed and scrape away any mulch or leaf litter that might inhibit the sun from reaching the soil. Wet the ground periodically to ensure the soil stays moist where the seed has been planted.
Of course, if your seed sowing is unsuccessful, you can always buy the plants from us. They are offered late spring all the way through the fall. Be sure to check our online inventory for availability.
What is your opinion regarding not planitng milkweed along the coast? I have recently read info regarding this issue. (Huntington Beach)
I am not familiar with the problem of planting native milkweed on the coast. If possible, please provide a resource for our blog readers.
What I’ve read warns that planting non-native milkweed on California’s coast is linked with higher incidence of disease. Native milkweed, which doesn’t allow for winter breeding, is less of a problem, although 67% of Monarchs tested in California were positive for Ophryocystis elektroscirrha (OE), according to the University of Georgia’s Project Monarch Health. To promote healthy Monarch populations, plant native milkweed.
Your guidelines for planting narrow leaf milkweed direct to soil is to plant in spring, but other sites say that mid october is the best time to place seeds directly into the ground. Who is right?
Both, if the seeds are stratified. If they aren’t, they either need late fall planting to allow them a cold spell, or stick them in the fridge a month or two and then plant in spring
Another native seed company also warned about planting even native milkweed on the coast because it may attract Monarchs away from their native habitat to a more foggy environment where they are susceptible to fungal infestation. It also depends on the definition of the coast. I live in West LA about 3 miles from the ocean. Calscape has a great map of LA that shows that my neighborhood is part of the narrowleaf milkweed range but Venice Beach or Marina del Rey about a mile westward is outside of the zone.
Kitty – that’s pretty much the issue of planting the Tropical Milkweed (non native). The issue isn’t just related to the coast however. (I’ve seen it planted outside Wrightwood). Anywhere it is watered, it will grow.
Last month a rep from the CA Dept of Fish and Wildlife said no milkweed at ALL within 3-5 miles of the coast (both native and non native), stating that milkweed doesn’t generally grow in this area. Adult Monarchs will continue to breed if they have milkweed, disrupting the migration cycle. Take away the milkweed and they stop breeding.
I agree with ridiculous. When I moved to pensacola (fl panhandle on gulf of mex) I drove for a living along coast and saw tons of monarch on their journey to Mexico. Now ten years later last year I saw less than 5. I will be planting and sharing info and seeds with as many as will listen.
Ridiculous. I live about a mile from the coast and have successfully grown narrow leaf milkweed from seed (at TPF). Actually more successful than purchasing plants.
Diane Pollock: You’ve missed the whole point of the discussion. It’s not that you can’t grow them successfully near the coast, it’s that you *shouldn’t* because the milkweed doesn’t naturally occur there and the butterflies will be distracted by the plants and want to lay eggs on them when they should be migrating.
A consideration… just because milkweed grows well in your coastal area, doesn’t mean it’s a good thing for monarchs, as others have pointed out. I have read that cautionary note many times and places.
Yes you can grow milkweed at the coast but shouldn’t within five miles of it. It is detrimental to the life cycle of monarch butterflies. Grow nectar plants instead and butterflies will come.
Thank you! I am definitely going to do this.
I grew 3 milkweed species from T.P. seeds last year and had a very high germination rate.
I also bought milkweed seeds from TPF and sowed them a month ago. Interestingly the ones put in seed starting mix kept moist in shade germinated only one seed but those put in ground in a very sunny spot have germinated successfully. So sun and not too much moisture is key.
Do you recommend cold moist stratification for A. eriocarpa? So much I’ve read about growing milkweed recommends CMS; however, since our southern CA winters are so mild, I can certainly see why our CA milkweeds might not need CMS. Thanks so much for your timely post.
No treatment necessary.
I read something on-line about cold stratification for milkweed seeds. HOwever, I think it was talking about species other than the California native species of milkweed. I planted mine (A. fascicularis seeds from your nursery) indoors in small pots almost 4 weeks ago and nothing is happening – any suggestions? I have kept it well watered and although they are inside they are in a south facing room with windows on 3 sides of the room – lots of light.
Well you missed the most crucial step which is to wait for the correct season (Spring and Summer… this year it’s later than normal). Though the seeds that you planted should still come up eventually it likely won’t be until April.
Do I have to stratify the showy milkweed seeds before planting
No stratification is necessary.
Please correct me if I’m wrong, but I was under the impression that the seeds needed to experience a hard frost prior to sprouting, otherwise they can’t sprout through the shell.
Some seeds do need a hard frost to germinate, but milkweed seeds do not. Most of the areas in which milkweed is found are frost freeze zones. In fact, many California plants do not need a frost to trigger germination, but it is on a species by species basis. As the blog points out, milkweed won’t germinate until the soil starts to warm in late spring. Happy growing!
The paperwork with my order of A fascicularis says “Cold stratification required!” but there is no mention of cold stratification needed in the online instructions from you. What is correct? If it is needed, how long????Thanks, Suzanne Lasseigne, Redwood City, CA
So, is it too late now to plant the seeds I just received from a friend?
Think of it as too early. Plant them in the spring (from March on) when they would germinate in the wild. During winter, local milkweed are dormant. This coincides with the overwinter resting of the monarch butterflies.
I had great success from seed with your Asclepias fascicularis.
I planted in june and they turned in marvelous tall plants that attracted monarchs, aphids(so many) and lady bugs.
2 questions—they never developped buds or flowered. Were 3 miles from coast—would this maybe be due to not enough consistent heat? Anything else?
2. Does dormancy look like the plant dropping all its leaves and being empty stalks? Unsure if the aphids finally had their way
Hi John – Sorry for the delayed response. No buds or flowers may be from too much shade or not enough heat (you planted in time for flowering before winter dormancy). This species does not grown naturally that close to the coast, so chilly overcast weather may have been a factor. When dormant, the plant leaves and stems turn brown. Tidy up by cutting back to stubs. The plant will reemerge in spring! Aphids don’t usually hurt the plants, as natural enemies (lady beetles, syrphid flies, lacewings) keep their numbers at tolerable levels. Good luck with your garden!
How many hours of sun are recommended? This whole discussion has been very helpful. Thanks.
Thank you Lili. I never noticed any dormancy as the Monarch caterpillars devour them practically down to the ground. But I will keep a more careful track of them if they do develop.
Hi! I am preparing to plant some milkweed seeds purchased from TPF. I bought both narrow leaf milkweed and showy milkweed but have since discovered that showy milkweed is not endemic to Southern California coast (I’m located in Santa Monica about 1.5 miles from coast). Should I just plant the narrow leaf? I don’t want to plant anything that might disrupt natural monarch development. I can always pass along the other milkweed seeds to friends who live in the right spot. But if it is ok to plant would love to have multiple milkweed varieties to support the monarch caterpillars. Any advice is appreciated.
I have a drought tolerant front yard and have been into native milkweed since 2015.
1) Some plants I buy and plant do not return. Can there be any shade? Or does it have to be 100% sunlight?
2) I have never had flowers the first year I put in the plants. Partial shade issue still?
I just bought some of your seeds. We’ll see how I do.
Thanks, Brian P.
My milk weed plant has pods that are now seeding. As I am reading your blog , I see you are saying to not plant until spring.
My question is what should I do with the seeds while I am waiting?
Don’t lady bugs eat monarch eggs as well as aphids? Also we found out that praying mantises were killing the monarch caterpillars as well as killing those that went into their chrysalis. Any safe way to keep the monarchs safe from these bugs?
Great post, thank you! If I just harvested seeds of my plant (November), what’s the best way to store them until spring?
Hi! I bought showy milkweed seeds from Theodore Payne for my mom’s garden in Los Angeles because the flowers were so pretty, but I just read on Calscape that it’s natural range doesn’t include SoCal. Is it still alright that we planted it?
What is a good time to move seedlings into the ground in western Contra Costa County?
Just wanted to thank you for all the information. Starting seed planting 3-1. ?( cant wait:))
Thank of you who read this blog and care for the monarchs.
Spread the word to stop planting non native milkweeds every chance you get. I always tell people at garden centers when i see it 🙁
When does your nursery typically sell Asclepius plants? I just purchased seeds but am not sure when to plant them. I live in Sylmar.
How many days does it take seeds to germinate, usually? I’m trying to start some Asclepias eriocarpa from your seed and I just want to know, if they don’t sprout, when to give up and start again! 😉
Esther, the only source I could find as to the time it takes for milkweed seeds to germinate comes from the reputable “Monarch Watch” group’s website (https://www.monarchwatch.org/milkweed/prop.htm#:~:text=Most%20seeds%20will%20germinate%20in,the%20flat%20from%20the%20bottom.) which says “Most seeds will germinate in 7-10 days if…maintained at 75˚F”, so I would give them about 2 to 3 weeks to germinate with southern Californian spring/early summer temperatures. Hope this helps!
Hi, Esther –
I purchased some showy milkweed seeds from TPF that I sowed in the ground around the time you posted this comment. Germination happened within 14 days. The first four test seeds all sprouted. These were in a full sun area that was deep-watered once a week. Hope this helps and hope you got seedlings!
We just ordered two A. eriocarpa seed packets from TPF, but only have room to plant one this year. Do you think the seeds will be viable next year? Do you know for how many years they remain viable? Thanks!
Thanks so much for this! I would love the addition of when to transplant. Today I noticed my bevy of seedlings in very small seed pots seemed to be dying off. They still looked so small. but I picked up a few and discovered the loooooong taproots coming out the bottom which I imagine might have led to their demise. The question is, at what point is best to plant in the ground? Thanks!
I am having a difficult time germinating kotolo milkweed. I get about 3 out of 64 seeds. Any suggestions?
I am still learning with the eriocarpa seeds. Something that helps a bit is to wash the seeds very thoroughly. I wash my hands with a clarifying shampoo or dish detergent. After mostly rinsing my hands, leaving a little residual detergent, I take some dry seed seeds and rub them between my hands. Then, I rinse them very thoroughly multiple times. The reason I started to do it is because the eriocarpa seeds seem to easily get a white fungus growing on them. Cleaning them greatly reduced the fungal growth. They take a long time to germinate so I think reducing the fungus problem helped my success rate.
When is the best time to transplant? My narrow leaf milkweeds are 6″ to 10″ high are are in 3×3 and 4×4 pots, all 3.5″ deep. I don’t see any roots coming out of the bottom yet. I live in central Contra Costa County and have some hot summer days ahead.
Clearly I made a mistake when I acquired a narrow-leaf milkweed plant and planted it in a mostly shady spot. It did grow, didn’t flower, and went dormant. Last year it reappeared in the summer, didn’t flower, and went dormant again. I want to transplant it to a completely sunny location in Chino Hills. During what month should I transplant? Any other suggestions?
I would buy new plants for the sunny location right away so you have lots of milkweed in any case. Most milkweed plants in the ground are not easily moved so moving it may kill it. Please try it and report back.
Most milkweeds have a taproot. If you are moving it, you would need to dig it up while it was dormant (Oct/Nov) and not damage the taproot. That’s a lot of work.
If the plant has grown side plants, you could just dig those up as soon as the plant goes dormant, and then replant those. They are more likely to survive. I’m not sure if narrowleaf has rhizomes or not. If so, you can replant the rhizomes and they will grow.
I haven’t tried moving one before. As a drought tolerant plant, it’s root system could be deep and a hassle to move. We would appreciate knowing what you observe while digging and what happens.
For narrowleaf milkweed, I have been using the “water germination” method described at grow milkweed plants web site. Water germination yields about 50%+ success. Essentially, put seeds in water at about 70F and they will germinate in a few days. Change water twice per day. When the root is a few days old, I put it in a pot. In a couple of weeks, the plant pops up.
I haven’t had great success using water germination with other varieties like eriocarpa. Others have a low success rate for me.
Hello, I supply several elementary schools in the Downey area with milkweed plants. Can I purchase 300 narrow leaf seeds from you.
I no longer will use Tropical milkweed.
Thank you, Frank
Hi Frank, you can order milkweed seeds in our online store at store.theodorepayne.org, or visit the nursery to purchase them Tuesday-Saturday, 8:30-4:30.