Gomphocarpus Physocarpus

Balloon Plant for Monarch Caterpillars

Gomphocarpus physocarpus: Asclepias physocarpa is the former botanical name, Goose plant, Giant swan milkweed, Hairy balls, Family jewels, Oscar, Cotton-bush, Balloon plant

Asclepias physocarpa (ballon plant) pods
Great Balls of Milkweed!

Plant Specs:

  • Perennial for USDA hardiness zone 8 and above (lows -12.2 °C or 10 °F)
  • Fast growing annual for colder zones
  • Full sun to part shade
  • Height: 4 to 6 feet (can grow taller)
  • Spacing: 2 to 3 ft
  • Flowers: white with purple accents
  • Blooms mid to late summer
  • Not the same plant as its bushier brother swan milkweed

Plant Propagation:

  • Start seeds indoors 2 months before final frost
  • Sow seeds directly after final frost (not recommended below zone USDA zone 8)
  • Soak seeds in warm water 24 hours before planting
  • Stem Cuttings
  • Leaf cuttings
  • In annual zones, balloon plants are better if you can find them locally or online
Balloon Plant Milkweed Flowers are Creamy White with Pretty Purple Highlights. The flowers contrast nicely against dark green milkweed leaves.
White Elegance with a Hint of Purple Passion


  • Fastest growing annual milkweed
  • Can sustain lots of monarch caterpillars late season
  • Long stems with pods make amazing table centerpiece
  • Use long cuttings to feed caterpillars indoors
  • Last viable milkweed species before fall takes over


  • Colder hardiness zones must start seeds indoors for hopes of a seed harvest, or overwinter indoors under cfl light bulbs
  • Flowers aren’t super showy, but still pretty
  • Up north, only pollinated by wasps (and one red admiral!)

Goose Growing Tips:

  • Start seeds indoors 1-2 months before avg last frost
  • Seeds germinate in less than one week with heat and moisture
  • Use an oscillating clip fan on seedlings to strengthen the stems to simulate an outdoor breeze…a must for strong stems!
  • Grow this as a back border so it doesn’t shade your other butterfly plants
  • Cut I- you can cut them back late spring for bushier growth
  • Staking may be required if not cut back in perennial zones
  • Cut II- Is fall setting in before seeds are ready to harvest? Take stem cuttings with the largest pods (leave seed pods attached) and place them in water. This should give them the time they need to finish developing.
  • Don’t force open seed pods…they will start to open when they are ready
As the peculiar pods of Balloon Plant Milkweed start to ripen, they'll take on a deep sunburn. The September milkweed leaves  remain viable for feeding late-season monarch caterpillars. More Photos, Info & Seeds...
Almost Ready…
You'll know balloon plant milkweed seeds are ready to harvest when the seam starts to split, revealing the dark brown seeds inside. If the seeds aren't ripe before your first hard freeze, take a stem cutting from the plant (with the pods attached) and put it in a vase inside. This will give the seeds a couple more weeks to fully develop.
Open Sesame!

Pollinator Plus:

Not much to report up north. The only pollinator I’ve noticed visiting this milkweed on a regular basis is the blue mud dauber (black wasp). If you have noticed other pollinators on the goose plant, please leave a comment below.

nature note: Though the mud daubers look ominous, they have never shown aggression. They’re also frequent visitors to our swamp and tropical milkweed plants.



2. Find More Balloon Plants Seeds on Etsy

One more time: starting seeds indoors early will give you a huge jump on the season and is a must for northern gardeners. This milkweed species is a rare find in nurseries, so seeds are probably your only option in most regions.

Click here to Explore other Milkweed Options for your Butterfly Garden

Please post below if you have any questions or comments about growing Asclepias physocarpa in your garden:
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  1. says

    By the way – they call G. physocarpus Bishop’s Balls in the UK and you can buy seeds and plants there. They sometimes get Danaus plexippus in the UK and a few people raise them.

    It grows so big here in NZ that I call it a “testicle tree”.

    • says

      Hi Jacqui, thanks for the UK info and the scandalous new nickname. I tried to overwinter one so I could get a ‘tree-sized’ plant this season, but the plant died mid-winter. Maybe next year? I hope all is well in NZ!

    • Brenda Naylor says

      Brenda Naylor I bought 8 of the balloon plants at a nursery were I live in central Florida.Iknew nothing about them accept they were milkweed for monarch then I saw the balls come out and went on the site.Will Ineed to start seeds in doors?

  2. Judy Thompson Parkey says

    I bought several plants of this species last year, 2013, and enjoyed growing it. It made a small annual tree, of sorts, behind a back flower bed. The butterflies loved it, looked great in floral arrangements and I had a lot of fun with the name. I didn’t buy it again this year as it is not available locally. I had bought it 3 hours north of where I live. I wondered if any seedlings would come up as the seeds in the cotton like fluff blew all over the neighbor. Just yesterday I noted a “weed”. I started to pull it and then thought better. I thought I’d give it awhile and see what would happen. I’d forgotten all about the hairy ball plant. Then…it came to me…”great balls of fire…that’s the hairy ball plant!”. The seedlings are 4″ tall. I have 100 days before the next freeze…hopefully that will be enough time to see the plant in all its glory.

    • says

      Hi Judy, congrats on your physocarpa seedlings! They probably won’t mature this season but you can overwinter them indoors and start with some plants next season. I brought in four last fall.

  3. Dana says

    Hi Tony

    Some time ago, you mentioned you were going to try propagating Oscar from leaf cuttings. Did you have any success with that? If so, how did you do it?


    • says

      Hi Dana, I was not able to root physocarpus in water, but I am still going to try planting cuttings in soil (with rooting hormone) at the end of the season. I will be sure to update the page with my results.

  4. says

    I germinated from seed last summer and they grew several feet but never flowered. I live in Maryland in Zone 7. I didn’t plant any this summer but have a nice patch of them growing again this summer in the same place they grew last year. They must be growing from last summer’s roots?

    Have you ever heard of them growing perennially in Zone 7? We had a very cold winter last year as well.

    • says

      Hi Scott, if you want them to flower and seed in your zone, try starting them indoors 2 months early OR overwinter plants and start cuttings. They are not cold hardy to your zone so I’d be surprised if they came back, but gardening is full of mysteries and miracles so it’s definitely possible. If they did, it didn’t give you much of a head start. We overwintered 4 in Minnesota and they are already forming pods.

    • says

      Hi Sunila, while it does make an interesting showpiece in the garden, or cut for a vase, our main use for it is to attract monarch butterflies to lay their eggs on it.

      • Susan says

        What I’ve learned about this is that, native milkweed makes the caterpillars toxic to birds. The gomphocarpus and other exotic milkweeds do not have this effect. So while I had 17-20 Monarch caterpillars on my plants, they were almost all plucked off by the birds! Food for thought…

        • says

          Hi Susan, the gomphocarpus varieties and tropical milkweed have higher cardenolide levels than any of the native milkweeds.

          No matter which varieties you plant (both native and non-native), many predators have adapted to the poisonous nature of milkweed, which is why it’s estimated only between 1-5% of monarchs survive to become butterflies outdoors.

  5. Kerry says

    This is the first year I’ve planted the hairy balls variety and I love it. I’ve seen a Monarch caterpillar eating leaves and black wasps pollinating. Also, I snapped some pictures of a golden digger wasp visiting the flowers in August. I love in illinois and I’m hoping to save the seeds to plant next year. Thanks for the info on your site!

    • says

      You are welcome Kerry! If some of the pods are “close” to developing right before your first frost, take a long cutting and put it in a vase. You’ll have an interesting centerpiece and the seeds should ripen to maturity.

  6. Darlene Suarez says

    Yesterday I was given one of the balls with seeds. Today it popped open emitting the seeds. I live in zone 9b in Southern California. Should I start them indoors too and overwinter them inside or can I plant them directly in the ground? If starting them indoors how many seeds should I put in a pot? What size pot do you recommend? Fertilizer in the pot? Thanks for any help.

    • says

      Hi Darlene, physocarpa is cold hardy to your region so there is no need to extend the growing season by starting indoors. I would still soak the seeds before planting, but direct planting should work well for you.

  7. says

    Right now in Lake Forest, California Green Thumb International has these plants in one gallon sizes with balls and all!

    This is the first year I have ever seen them here and I have been raising Monarchs for 9 years now.

    I am now the proud owner of 3 of these plants. I love them!!

    • says

      Nice fine DeeDee! I pulled out all our plants today but did make a table centerpiece with a few of the stalks to get more seeds in the next couple weeks. Enjoy the rest of your garden/raising season in California!

  8. Sherri Noble says

    Thanks Tony for sending this link to me through The Beautiful Monarch! Very great information you have here as always. I have never seen such an interesting seed pod before. I tried to open one and found a green pod inside. How long will it take for the pods to be ripe? How do I avoid the fluff blowing all around in my condo if they pop?

    Thanks bunches,

    • says

      Hi Sherri, don’t worry about physocarpa popping. They open very gradually. When you notice a seam starting to open on the pod the seeds are ready to remove. Don’t remove them before, or they may not be viable.

  9. Brian says

    Hi Tony,

    A friend of mine just cleaned out his garden and told me that he was going to give me some milkweed seeds. Little did I know that he would be handing me three seed pods the size of small oranges. None of the seed pods are open, and by the time I got home to research what type of milkweed seeds he gave me, it was to late to grab a stem cutting.

    Do you think I should keep the seed pods and hope that they will finish developing, or are they doomed since they are no longer on the plant (or stem cutting).


    • says

      Hi Brian, they aren’t going to develop further if they have been removed from the stem. If the pods are purplish, you may be in luck and get some mature seeds, but if the pods are green the seeds will likely be white and not viable. My last seed pod finally finished developing. The seeds take a LONG time to ripen. Good luck!

  10. Wendy Wissler Luckenbill says

    Just bought from local farmers stand . SE PA USA. Farmer said they spread by seed for her. We also had very cold winter but with heavy snow cover.

    • says

      Hi Wendy, I think most milkweed seeds can survive cold temps but there is typically much less seeding from warm weather varieties. We even have some tropical milkweed that reseeds in Minnesota. Physocarpa overwinters pretty easily. Good luck with your plants!

  11. Craig Popov says

    Hi Tony, I noticed this AM that I had at least 10 cats on my Scarlett MW and very few leaves left on my 5 plants so I rushed to the nursery and bought 2 more plants, but while there they showed me several physocarpa that look really good but I hesitated. Meanwhile wasps are killing my cats so I brought my 2 new plants inside and picked 12 cats off outside and brought them in!!

    My big question is, will the physocarpa do OK here? I am in zone 9B or 10A, depends on what chart you look at.
    If so are they a good companion with the Scarlett?
    Or should I get another species? My ground is very sandy and usually pretty dry! Thanks and MERRY CHRISTMAS!!

  12. Jackye says

    Hi Tony
    Asclepia’s are very good at deterring moles. A few stems with leaves in a mole hole will have them scampering away – possibly to the neighbors garden. :)
    I’m not sure if the plant gives off a scent/pheromone or if it is the milky sap – but it works. Planting the plant does not deter the moles – so the deterrent does not come from the roots.

  13. Shirley Barnhart says

    Hi, Tony. I bought one of the “Goose plants” (it was labeled “Family Jewels”) thru mail order last October, & I immediately planted it outside. (Houston, Texas, zone 9a) It liked the weather & jumped in size, so I started taking cuttings. The first cutting rooted quickly (I passed it on), but after that, rooting them wasn’t so easy. I have had about a half dozen clippings, & I have only managed to get 1 more to root. After reading that they need “warm” water, I’m guessing that may be the problem. I think, if I do this next fall, I will use a heat pad! I am so looking forward to seeing how this interesting Milkweed is going to do! (I have been covering my plant during the “freezes” so that it will be ready for spring migration!)

    • Anna says

      Hi Shirley,

      I too live in Houston. I want to try raising a variety of milkweed but would be concerned about not cutting back before the spring migration. These plants can hold the O.E. Virus carried by infected Monarchs. If the plants are not cut back, the incoming Monarchs can rub up against or eat leaves with the virus left by last seasons virus carriers. As I am wanting to purchase other kinds of milkweed, could you tell me from where you buy yours?

      • Shirley Barnhart says

        Hello, Anna. Please forgive me for not responding before now…I somehow must have overlooked the notification in my emails!
        To answer your question about where I purchase my Asclepias plants… Have you heard of Zone 9 Tropicals, in Houston? I have purchased from there, as well as Nelson’s Water Gardens, in Katy, TX. I have been mail ordering from Annie’s Annuals and Perennials in CA. The only drawback from Annie’s, is that they have to spray them before shipping & you must keep them away from butterflies, caterpillars… any pollinators, for a minimum of 3 months. Other than that, Annie’s always ships healthy plants & they arrive in great condition! Their customer service is great, and they have a good selection of Milkweed,too! I have ordered 4 different ones… Davis, Virginia Silk, Wild Cotton, Family Jewels & Thin Leaf Milkweed. My Wild Cotton & Family Jewels have survived, & both have had eggs & caterpillars this summer. My luck with the Davis, Virginia Silk & Thin Leaf Milkweed, has not been as good, but I haven’t given up, yet. Maybe I will get them to survive next summer!
        I want to comment on your concern about protecting the butterflies/caterpillars from the virus that Asclepias can carry. I, too, am very aware of it, & I will cut off a branch(es) from my Milkweed, if I don’t think it looks healthy, any time of the year! I also trim ALL of my Milkweed down to 6 to 8 inches in the fall, although I stagger trimming them, by areas, so that I don’t strip all the leaves away at the same time, just in case there might be eggs/caterpillars that will need food! Last winter I had caterpillars into December & chrysalis’s that hatched throughout our winter! And, because I cut my plants down in the fall, I had healthy, full plants for the spring migration! (I do protect many of my plants from freezes, too. I use buckets, flower pots, even trash cans to cover plants, & I always remove the covers after the freeze threat passes!)
        It is very important to cut the plants down so that they can restart & be fresh, but you don’t have to wait until the spring!
        Good luck with your plants! Maybe someday I will run into you at Nelson’s Water Gardens or Zone 9 Tropicals!

  14. says

    Hi Shirley, you are probably correct about the rooting issue relating to cool water temperatures. I’m sure if you try rooting some in late summer you’ll have better results. Physocarpus should probably grow well as a perennial in your region. If the monarchs used it at all during the fall, you might want to cut back some stems so fresh growth can emerge, the same as you would do for tropical milkweed. Good luck with your new plants…

  15. Seana Parker-Dalton says

    Caterpillars stripped my tall tree that I bought, then it died from lack of water–(I had a baby and no one tended the plants for a few days). I was able to germinate several seeds though. They grew to about two inches high, then lost their leaves several months ago. All of the stems are still green and alive months later, but no leaves. I am totally confused! Has anyone else ever had this experience? I am in Florida, so they have been outside most of the time, aside from a couple when I brought all my plants in in to let the potted tropical mw grow back and to keep butterflies from laying eggs on and eating my seedlings. (The swarms of monarchs I had a few months ago seem to be gone for now. )

    • says

      Congratulations Mama!

      you did not say where you are in Florida? Perhaps the plants go dormant over your Florida winter? You might want to talk to someone in your region who grows this or a local nursery to get some “Florida” insight. Keep us posted on your plants…

  16. Chris Howells says

    Has anyone had an itching/burning sensation on arms after working with Asclepias physocarpa? I was recently smashing and rinsing aphids from my plant and when finished, about 15 minutes later, had a very unpleasant burning/itching sensation on my arms?

    • says

      Hi Chris, I’ve never heard of this happening to others handling physocarpus. Perhaps you were exposed to more sap because of your aphid removal technique? Maybe it was was an allergic reaction? If it happens again, I would wear gloves when handling the plants.

    • Shirley Barnhart says

      Hello Chris… As Tony said in his response, you probably made contact with the milky substance from the plants. Take this as a warning… You might be extremely sensitive to the plants, so it would be best to wear long sleeves/pants & gloves anytime you work around & in your Milkweed!
      Also… DO NOT LET ANY OF THE MILKY SUBSTANCE GET INTO YOUR EYES!! I have been there, done that, & it isn’t a fun experience, let me tell you!! Even though I flooded my eye with water for multiple times, several minutes each time, I still had to go to a Emergency Clinic, which put me thru another serious eye rinse process… they gave me some kind of pain killing eye drops when I first got there, which eased the burning & tricked me into believing that I was thru the worst of it, but, within a few hours, the horrific burning came back, & my eyes had become so sensitive to light that I sat in a dark room with dark sunglasses on & even the dimmest of lights felt like a dagger in my eye! I had a miserable night & was taken to an eye specialist in the morning, that determined I had torn a hole in my cornea! I was lucky, though, as my eye has healed up without having any long term complications that I could of had! My friends & neighbors all thought that I would stop growing Milkweed because of my ordeal, but, not a chance!! I love the butterflies too much to do that! I do have more appreciation for my eyesight, though, & I will be a lot more careful any time I handle Milkweed… and I warn everyone I share the plants with, to do the same! And now, I am warning you, as well as any one that should read this, to do the same!

  17. Rhonda Murdock says

    As soon as we planted the balloon plant, the butterflies immediately went to it and planted their eggs. The birds kept eating the caterpillars so I put a wire fence around & on top of it so that the butterflies could still get in but the birds can’t. I don’t understand why some of the caterpillars are falling off and walking away from the plant now. I went from, at one point, having 11 to now having 4. We also bought 2 of the Tropical Milkweed and the butterlies are ignoring those.

    • says

      Hi Rhonda, if you just purchased the plants, they might have been treated with pesticides or they could have OE spores or bacteria that are making the caterpillars sick. If possible, it’s always best to have a healthy supply of milkweed (home grown) before raising monarchs.

      If the plants were treated with pesticides, I would suggest cutting them back so that healthy new grow can emerge. If pesticides weren’t used, you could always try raising a few indoors on stem cuttings after thoroughly rinsing the milkweed…good luck!

  18. Khaba says

    I have got a balloon milkweed, but I don’t know what the benefits of this plant are and what it’s used for?

  19. Linda Hayler says

    Hi Tony
    I have been given some of the seedlings and hope they do ok over here in the UK . I live in the sunnier south east, will they be ok overwinter?? do they need to come indoors??? Thanks Linda

    • says

      Hi Linda, please check out the zone info on the page to see if it is winter hardy in your region. If it’s not, you would need to overwinter the plants indoors or start seeds indoors early next spring. good luck!

  20. Mary says

    Hummingbirds have been pollinating my Gomphocarpus physocarpus. The Great Black Wasps have probably been there too, but I’ve only seen those on the tropical milkweed. I’ll have to bring the plant inside when the weather turns cold, but I’m hoping that the seedpods will continue developing under lights.

    • Mary Arneson says

      Update: the Gomphocarpus is inside now, and the seedpods are continuing to enlarge. They were less than half an inch across when the plant came indoors, but they are more than an inch in diameter now.

  21. Fran says

    Hi, I am in North Carolina, Zone 7b. Will this plant grow here as a perennial? Or would I have to bring it in to overwinter?
    Thanks a lot

    • says

      Hi Fran, you’re on the borderline for hardiness. If you leaf mulch the plants before winter they might come back. Otherwise, you could overwinter indoors or start seeds indoors next spring.

  22. Margaret Furby says

    I ran out of milkweed in Sept., 2015 and bought some which I think had been treated because I lost a lot of cats. My question is: I am rooting in water a bunch of the stems I cut to use. Are these cuttings from the parent plant contaminated? Most of the cuttings have a lot of apids. Does that mean I can use for eggs and cats next summer?

    • says

      Hi Margaret, typically pesticides can last from weeks to even months depending on what type was used and how much. I would guess it would be fine to take cuttings to start new plants, but again, it’s hard to say without having all the details. good luck!

  23. Carrie G says

    I have balloon plants reseeding all over a large lot in Oakland, CA and am giving away the seedlings. Two questions: When should I look for eggs since the plants go strong year-round? Should I let the lady bugs and aphids duke it out or spray the plant with a hose to remove the aphids?

  24. Mary says

    I live in Los Angeles and my neighbors milkweed, hairy balls, are starting to seed. I collected some of the seeds from the pods that have opened. When & how do I plant the seeds?
    Thank you,

  25. Derek says

    I have had a huge issue with Aphids. I’m trying to look for a natural way to fight them. I have used probably 500 ladybugs and about 100 lacewings and they hardly dented the problem. I ended up using neem oil and that works but don’t know the damage to caterpillars from the oil. Do you have any suggestions.

    From northern california

    • says

      Hi Derek, aphids are the bane of butterfly gardeners across the country, so I’ve compiled a list over the past few years on how to combat them. We haven’t had an infestation in our northern garden since 2011, and over time we’ve seen more aphid predators as our ecosystem has developed naturally. It’s a good idea to expand your selection of milkweed varieties and have several patches around your yard and garden. That way, there is usually some that will be aphid-free. Here are some ideas that can yield instant results:

      How to stop Aphids from taking over Milkweed

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