Gomphocarpus Physocarpus

Balloon Plant for Monarch Caterpillars

Gomphocarpus physocarpus: Asclepias physocarpa is the old 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

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 in warm water
  • 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
  • Flowers aren’t very showy, but still pretty
  • Up north, only pollinated by wasps (and one red admiral!)
  • Potentially difficult to overwinter? (I brought one in balloon plant that died. Perhaps it wasn’t getting enough light?)

WINTER 2014 UPDATE: I’m currently overwintering 4 balloon plants and they are all thriving under CFL light bulbs

SPRING 2014 UPDATE: All four balloon plants survived and have been successfully replanted in the butterfly garden.

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
Asclepias physocarpa milkweed pod starting to open up
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.



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:
Print Friendly


  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!

  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.

  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?

  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…

Leave a Reply

Your email address will not be published. Required fields are marked *