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Gomphocarpus Species, Balloonplant, Cotton-bush, Hairy Balls, Giant Swan Milkweed

Gomphocarpus physocarpus

Family: Apocynaceae (a-pos-ih-NAY-see-ee) (Info)
Genus: Gomphocarpus (gom-fo-KAR-pus) (Info)
Species: physocarpus (fy-so-KAR-pus) (Info)
Synonym:Asclepias brasiliensis
Synonym:Asclepias physocarpa
Synonym:Gomphocarpus brasiliensis


Tropicals and Tender Perennials

Water Requirements:

Drought-tolerant; suitable for xeriscaping

Sun Exposure:

Full Sun

Sun to Partial Shade



Foliage Color:

Unknown - Tell us


36-48 in. (90-120 cm)

4-6 ft. (1.2-1.8 m)

6-8 ft. (1.8-2.4 m)


36-48 in. (90-120 cm)

4-6 ft. (1.2-1.8 m)


USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

USDA Zone 10a: to -1.1 C (30 F)

USDA Zone 10b: to 1.7 C (35 F)

Where to Grow:

Unknown - Tell us


All parts of plant are poisonous if ingested

Bloom Color:

White/Near White

Bloom Characteristics:

Unknown - Tell us

Bloom Size:

Unknown - Tell us

Bloom Time:

Mid Summer

Late Summer/Early Fall

Other details:

Unknown - Tell us

Soil pH requirements:

5.6 to 6.0 (acidic)

Patent Information:


Propagation Methods:

By dividing the rootball

From leaf cuttings

From seed; direct sow outdoors in fall

Seed Collecting:

Bag seedheads to capture ripening seed

Allow pods to dry on plant; break open to collect seeds

Allow seedheads to dry on plants; remove and collect seeds

Properly cleaned, seed can be successfully stored


This plant has been said to grow in the following regions:

Tempe, Arizona

North Little Rock, Arkansas

Arroyo Grande, California

Calistoga, California

El Sobrante, California

Encinitas, California

Long Beach, California

Palo Alto, California

Rancho Palos Verdes, California

Richmond, California

San Diego, California

San Jose, California

San Leandro, California(2 reports)

San Marcos, California

San Pedro, California

Vista, California(9 reports)

Denver, Colorado

Brooksville, Florida

Deland, Florida

Homestead, Florida

Indialantic, Florida

Port Saint Lucie, Florida

Saint Petersburg, Florida

Winter Springs, Florida

Buford, Georgia

Cordele, Georgia

Hilo, Hawaii

Barbourville, Kentucky

Louisville, Kentucky

Hammond, Louisiana

Dighton, Massachusetts

Dearborn Heights, Michigan

Minneapolis, Minnesota

New Milford, New Jersey

Averill Park, New York

Cary, North Carolina

Elizabeth City, North Carolina

Greensboro, North Carolina

Middletown, Ohio

Newark, Ohio

Oklahoma City, Oklahoma

Tulsa, Oklahoma

Portland, Oregon

Ladys Island, South Carolina

Ninety Six, South Carolina

North Augusta, South Carolina

Austin, Texas(2 reports)

Dallas, Texas

Los Fresnos, Texas

Richardson, Texas

Hampton, Virginia

Bellevue, Washington

show all

Gardeners' Notes:


On Aug 9, 2015, Homescuba from Newark, OH wrote:

I got one of the Giant Swan Milkweeds from a garden center in my town of Newark, Ohio I planted it it grew very fast it is over six feet tall didn't have to do anything to it just left it alone. I just got a few pods on it the last few days. Didn't see any butterflies around it but a lot of wasps on the flowers. I think I will try to grow more next year from seeds hopefully I will have butterflies next year. And I was wandering if you get catapilaters on the stalks.


On Aug 28, 2014, onebirdiema from NoVa, VA (Zone 7a) wrote:

This plant 'volunteered' in my vegetable garden summer before last. It was The Mystery Plant until someone from local Coop Ext id'd it for me. By end of summer we counted five monarch caterpillars crawling all over it. After frost I moved it out of the vegetable garden, but we then had a hundred-year cold winter and it didn't come back. I do, however, have seed in the gomphos I saved, and will be trying various things to germinate some. Then I propose to entertain the drivers on my suburban subdivision street by planting them along the curb . . . if they'll grow there, they'll grow anywhere! THanks for all the comments previously -- they are a big help.


On Sep 27, 2013, Domehomedee from Arroyo Grande, CA (Zone 9a) wrote:

I've grown this plant for three years now. They are easy care and a good source of food for the monarch butterflies. They do require full sun for best growth and when the pods look ripe I with withhold water to inspire them to finish seed production. The large pods always get comments from passersby. They are a large plant which is welcome as I no longer have more catapillers than I can feed. They had aphids the first year but they seem to like my other milkweeds more, which is good as I don't really like aphids at face height.


On Mar 17, 2013, AmandaEsq from Greensboro, NC (Zone 7b) wrote:

I purchased this seed from a reliable vendor who caters to monarch enthusiasts. My understanding is that it is an annual in my zone. The seed did not require pretreatment of any sort. I can't imagine why anyone here has identified difficulty in germinating the seed. If you have wild collected the seed it may be that the seeds weren't ready for harvest.

The plants grew to at least 6' tall and were alive well past frost here. I wondered myself if they really were going to be annual in my zone. We did have extended periods of sub-freezing temperatures this winter (unlike last) so I'll be watching the stalks with great interest. I collected a great amount of seed and will start more for this season.

If you grow this plant you should expect aphids. Milkweed... read more


On Mar 7, 2013, Leafhead from Madison, WI wrote:

I'm just starting out c Asclepias physocarpus seeds for my first time. I'm a long time butterfly gardener and this Asclepiad intrigues me as a host plant/ nectar source.
I live in Zone 4b (WI) and am hoping this will reseed itself here in the Midwest.
If all else fails, I'll keep some seed back for next year...


On Oct 5, 2012, fwingsuk from Warwick ,
United Kingdom wrote:

got these seeds in SA planted them in doors and everyone germinated six plants the rest are in the fridge the plants are in pots in the garden and have flowers on now but I think there will not be any seed heads as it is already 10c.
Can anyone tell me if I put these in a green house that they will survive till next year they are already 4 foot high with loads of buds on
many thanks


On Aug 23, 2012, wyopaul from San Diego, CA wrote:

the most important function this plant provides; in addition
to it's fun name and appearance; is that it is a Monarch
Butterfly attractant. The lady who complained about
caterpillars all year probably had a lot of monarchs
munching and making a mess, but what a bonus!
People who grow this plant in monarch areas are providing
much needed egg laying spots, and food for future generations.
I live in San Diego, and am seeing far more monarch in the yard, and yes, the caterpillars are munching.


On Mar 28, 2011, silkroad from Lady's Island, SC (Zone 9a) wrote:

I love this plant! I have found it easy to germinate, and the dried balloons look great with other dried flowers, or just piled into bowl on the coffee table. They always generate comment. The flowers, too, while not showy, are graceful and often the plant grows into a lovely candelabra shape. My friends always look forward to the seedlings I germinate for them.


On Aug 12, 2010, murchik from Pedricktown, NJ wrote:

I have limited experience with this plant so far-started it from seeds this spring. Seeds were from 2 different sources. One pack from Chiltern Seeds, UK; using baggie method, half w and half w/o cold stratification none germinated. Another pack from Hardyplants; using baggie method, soaked seeds in 100 F and let sit overnight-7 out of 10 seeds germinated. One germinated during original overnight soak, the other 6 in a baggie within a week.
jxbrad14 I saw this plant in Longwood Gardens this year, too. Unfortunately, there was nobody around at the time to ask if it survives the winters or they grow it as an annual.
Maybe, the seeds you picked were immature or they might require a period of dormancy to become viable.
I have my seedlings planted out in two places in t... read more


On Jun 10, 2010, jxbrad14 from Lansdowne, PA wrote:

Found seeds on a plant growing at Longwood Gardens, Kennett Sq. PA. and tried sowing them outdoors and indoors into peat moss pod. Out of 20 seeds none germinated.


On Feb 21, 2010, jlp222 from Hammond, LA (Zone 8b) wrote:

This is the first Milkweed I grew. I planted about 10 seeds directly in my garden and 2-3 grew (my fault not the seeds, I was a beginning gardner). This was 3 years ago. Last year, only 2 came back. One grew very bushy to about 4 feet. The other to a lanky 6 feet. They are a caterpillar beacon! They were covered all summer and into fall. Also, I had a problem with aphids. There had to be thousands of them.

The seed pods ("balls", hehe) are so very interesting that I would grow this plant for those alone. They are amazing cut and dried, and everyone who walks past had to ask about them.

So pretty much you have:

Strong grower
Give butterflies and caterpillars a home
Very cool seed spods

Cons:... read more


On Jan 25, 2010, Arline from Palo Alto, CA (Zone 9a) wrote:

I live in Palo Alto, CA and have grown this Asclepias for 2 years. The branches make a wonderful dried arrangement and it is a real attention getter at over 6 feet when the swollen seed pods sway in the breeze. No cats yet though.


On Nov 8, 2009, SusiS from San Leandro, CA wrote:

I planted it from seed last fall, and now it is about 8 ft and growing. I am not sure if I should cut it back in the winter. It is growing above the roof!


On Nov 12, 2008, VGMKY from Louisville, KY wrote:

This was my first year growing Oscars Milkweed or asclepias (Gomphocarpus physocarpus) here in Louisville, Kentucky. It did outstanding growing to better than six feet tall. I volunteer at a local nursery and was able to germinate the seed there in late March. and transplanted them in early May. There is a 120/130 days needed for maturity. being late Summer/Early Fall with flowering and pods. With high heat and dry weather it was drought-tolerant.
Seed saving can be a challenge; I didnt want them to dry attached to the fluff so took the mature pods and separated the seed from the center of the pod and using my fingers rubbed the seed and they detached themselves into a container for drying. I found this method helpful to me rather than having the milkweed fluff escaping in... read more


On Nov 9, 2008, kittysue from Fairborn, OH wrote:

Seed are slow to germinate. The plant is a fast grower in ordinary potting soil, and relatively free of oleander aphids.


On Sep 6, 2007, flamingonut from New Milford, NJ wrote:

A beautiful tall milkweed. Earlier on, it had quite a few tiny monarch cats on it, and I believe the high amount of wasps & predators did them in. I've seen conflicting hardiness info on this, ranging from Z7 thru Z10 and Z9 thru Z10. Regardless, it's a must have annual for us northerners. Hopefully I'll be able to harvest seed so I can grow more next year. It just started blooming in NJ, late August, originally wintersown.


On Dec 25, 2006, ineedacupoftea from Denver, CO wrote:

Similar to Asclepias fruticosa, but a larger plant in general; also from South Africa.


On Oct 8, 2006, hedgwytch from Tulsa, OK wrote:

This is a monarch magnet! I grew four other Asclepias in my garden this year, and this was the one that was consistently covered in cats all season long. The seed pods are a definite conversation starter! This plant gets a thick stalk and about 7 feet tall in Z7. The flowers are small, cream and pale lavender, and hang in clusters. I plan on adding several more to next year's garden. This is a must-have in a butterfly garden.