Spring Sowing Containers for Annual Milkweed

Spring Sowing Containers are a faster, easier way to start warm weather milkweed seeds including tropical milkweed. Learn the differences between spring and winter sowing and discover how to give your milkweed seedlings a huge head start each spring...

In the quest to attract and support more monarchs, I’ve implemented many effective time-saving techniques for raising them.

Over the past decade, I’ve also tried many milkweed propagation techniques to learn how to grow more milkweed, with less effort.

Winter sowing has been one of our most effective techniques for starting native milkweed varieties that need cold moist stratification.

However, it’s not a good option for warm weather species including tropical milkweed, swan milkweed, or balloon plant.

This year I discovered that cold treatment can be effective for these heat-loving milkweed varieties with a couple minor tweaks to the process…

Spring Sowing Milkweed

In early March, I added two new sowing containers to the winter sowing containers that had been sitting outside since early February.

These spring sowing containers were set up exactly like their winter counterparts. The only differences were that they contained warm weather milkweed varieties and the seeds were not exposed to bitter winter temperatures that would kill them.

Steps for Spring Sowing Containers

1. Choose your sowing containers

2. Follow this 11 Step Sowing Process


2a. Put the seeds in a wet coffee filter inside a sealed food storage container. We placed swan milkweed seeds in our 3-season porch (in March) where they were subjected to spring’s bipolar mood swings. The results were astonishing:

An easier way to propagate warm weather milkweed varieties and other annual seeds. More info on Spring Sowing Containers...

After the seeds have germinated, plant them in a sowing container. We kept ours in the porch, but you could also place it outside if the container lid has been taped securely.

3. Remove the lids from the containers

After the threat of frost is over you can permanently remove the lids. If temps get down to freezing post-lid, temporarily move them into the garage.

A common question I receive is how to separate the seedlings for planting. As long as you’re careful, it’s not difficult to separate the tangled roots of tropical or native milkweed seedlings…it’s digging up mature taproots that can prove difficult!

I was able to successfully plant all the milkweed from the tropical milkweed sowing container and from the swan container in our porch.

If you want to give your warm weather or tropical milkweed seeds an easy head start, spring sowing containers are a great option. Please post any questions or share your experience in the comment box below…
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  1. Here in zone 6a, I wintersowed my tropical seeds right along with my perennial varieties. It worked really well for me in 2018, so I did it again this winter, and I set them out on January 3! As of April 7, I’ve got a lot of tropicals sprouting — more, in fact, than the perennials. I use multiple sprouting methods – cold stratification in the fridge and sprouting under T5 grow lights, water soaking and winter sowing. I figure if I bomb out on one, I’ve got insurance!

  2. In Florida now but heading back north to NY.
    Can I start my seeds here or will I have a problem when I go back north.

    1. Hi Pauline, I would buy small plants when you get back to New York. If you can’t find any locally, there is a vendor on the suggested stores list that specializes in tropical milkweed plants:

      Suggested Milkweed Stores

      Alternatively, if you currently have plants in Florida, you could take stem cuttings to start new plants in NY…those will grow much faster than seedlings. Make sure you clean the cuttings thoroughly to rinse of potential OE spores.

  3. I started to cold moist stratify my annual tropical milkweed in the refrigerator in early March and will sow it at the end of April in the greenhouse, to be transferred to the butterfly garden sometime in May or June when it’s strong enough to hold it’s own outside. I’m hoping a later germination of it in warmer Michigan weather will simulate a more favorable climate for it plus offer a more tender variety of host plant for the Monarchs. Last year my one Butterfly Weed hosted many caterpillars for 3 generations but for some reason was ignored by Monarchs as a 4th generation host.

    1. I should add, I’m also growing 5 other varieties of perennial native milkweed in the greenhouse to be used in the new butterfly garden. I started a week ago and today saw 2 plants poking their heads out of the soil!

  4. I saved all the seed pods from my milkweed last season (I think it must be tropical because I live near San Diego which seems to be the lower terminus for the West Coast Monarchs) but the baggie with them somehow got discarded (not naming names). A friend of mine with a field of milkweeds sent me some from Washington DC. I have them in 18 tiny seed starter greenhouses and this morning I noticed that quite few of them have their little grren tips popped through the soil. We had a giant butterfly migration, mostly of painted ladies a couple of weeks ago – the sky was filled with clouds of butterflies and I think I spied a few Monarchs among them if that’s possible. I made sure that I had a healthy leafy milkweed on my deck where they have been coming to lay their eggs for several years now. I haven’t seen any fly-bys by Monarch mamas but I’m ready for them with one large plants and a bevy of plants to come. I’m not sure it they will come to the East Coast milkweed (I don’t have a name for the specie) I hope they will be able to use it and will get sufficient nourishment from it. I am looking forward to a season of 3-4 generations. If they don’t seem to use the new milkweed, I will go buy some more mature plants. My plan is to have plenty of plants so that there is no waiting in my garden when the mamas come by. I was hoping to have a kind of hedge of milkweed – lots of plants in a row near a wooden fence where they might want to hang. This year I will lock the collected seeds in a vault so as to not lose them by next spring.

  5. I have read that growing tropical milkweed is detrimental for monarchs. I read that it is because it continues to bloom for such s long time that it interferes with the monarch knowing when to migrate.

    1. Hi Patti, there are a lot of ‘theories’ about tropical milkweed with no hard data to back them up. We have grown tropical milkweed for a decade and the last butterfly migrates south weeks before the tropical milkweed succumbs to cold fall temps. They are taking other environmental cues to head south, just like they always have…

      1. My nursery says that he will not stock tropical milkweed anymore because his long time monarch growers say it’s detrimental it’s becoming harder to find near where I live on Long Island Ny

        1. Hi Arlene, I’m not sure how tropical milkweed is a potential issue in New York. If you can’t find plants locally, there are lots of available options from online vendors:

          Suggested Milkweed Stores

    2. I’ve grown it 3 years in SE Michigan…they still know when to leave. The only real problem seems to be in tropical /subtropical regions that never prune it back and raises risk of OE.

  6. Is it too late (last week of May) to plant swamp milkweed seeds outside in zone 7a (Philadelphia PA)? I was gifted the seeds at the end of last summer, stuck them in the fridge, and then forgot about them. Would love to get some milkweed going in my yard for the monarchs! Thank you.

    1. Hi Jessica, I would give it a go and see what happens…the hotter it gets, the more stressed small seedlings will be especially if they’re not getting enough water… keep an eye on them and hopefully you’ll have some good plants by the end of the summer.

  7. Hi Tony!

    Been stalking your page for over a year now. Thanks for all the great tips! I live in the thumb of Michigan, and I think I may have saw 5 monarchs this Summer. Bummer. Anyway, looking to Spring sow some Tropical milkweed. Can the seeds take freezing temperatures? If I set them out in March, we are definitely not done with freezing weather. Even April 1 is a little iffy.

  8. OK so I am in Michigan and got a little over ambitious when some warm weather came around in February, started germinating some milkweed and to my surprise every single seed sprouted!! They’re in peat pots and an old strawberry container what do I do?! They’re easily out growing the containers the roots are growing through the bottoms of the peat pots!! I really don’t want them to die! But it still seems too cold and it’s mi so still have a possibility of frost or blizzard or sunshine!! What should I do w them I’ve got at least 20 sprouts outgrowing their started containers QUICKLY

    1. Hi Devon, this happens to the best of us. This is why I’ve switched over to winter/spring sowing containers. This is the first year I’m not starting any seeds indoors. I would transplant your current seedlings into small pots (or spring sowing containers) so the root systems have a little room to grow. For next season, consider winter and spring sowing…you still get a head start with less work:

      Winter Sowing Milkweed

      Spring Sowing Milkweed

  9. The spring sowing links brought me to the winter sowing pages. Is the process the same? Do the containers go outside already or are they kept inside? i do not have an indoor porch/heated porch. Basement is pretty warm though, but dark or sunny or part sun for indoor? Is the process like indoor spring growing seed? Can zinnias be sown this way? I have sown seeds indoor in the past. The biggest problem I seem to have is having them die when I put them outside as I am not around all day long to water the seeds. Guess I need to let them get bigger before sowing the plants outside.

    1. yes Regina, it’s the same process…the only difference is the timing. I have not used sowing containers for zinnias before but I will be very surprised if it doesn’t work. Plants that germinate outdoors don’t need to be hardened off, and are generally much sturdier for replanting. If you’re not having success starting indoors, what have you got to lose using sowing containers outdoors? You can also wait to try this method next season to see how I fare this spring….

  10. Once the Tropical milkweed seeda are started in the coffee filter, how many do you plant per pot and what size pot? Do you fertilize early on, even when they are on a “cool” porch?

  11. Hi! What is the best way to control those yellow aphids that distroy my milkweed plants each year? I have sprayed the Castile soap & water, used rubbing alcohol, put on rubber gloves & dragged my fingers down the stems to squash them. Sprayed them off with hose, They come back quadrupled ! It is discouraging to say the least to keep the plants healthy. Where do they come from? If from the soil, can I treat the soil with something? Many thanks for your help. This will be my 3rd year of raising Monarchs.

    1. Hi Jane, aphids are (unfortunately) a common butterfly garden problem across the world. There are both short and long term strategies for dealing with them. Two things that can help in the long term are growing different species of milkweed and utilizing aphid repelling plants like allium spp. Here’s more info:

      How to Stop Aphids from Taking Over Milkweed

  12. Will be planting organic milkweed (tropical) this year for the first time. Ordered the plants from an organic nursery. Would like to use a large garden pot. Any suggestions? I live in NC. Thanks

  13. Hey! I live in Central Florida (coastal). Is this necessary to do with the native milkweed plants or can i just direct sow in February? I am specifically wondering about the sandhill milkweed seeds. Also, can i plant some of the seeds now (early July) or will it fail to allow for enough time IF we get Winter frost?

    1. Hi Donna, spring sowing can help extend the growing season in colder regions. it’s not really necessary in your region and it probably doesn’t get cold enough to be an effective propagation technique.

      You can always try planting some seeds now, but seedlings often succumb to summer heat…fall/winter/early spring are better options for planting seeds.

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