Whorled Milkweed 101 – Ultimate Grow and Care Guide


If one of your goals is to provide habitat for Monarch Butterflies, then Whorled Milkweed can fill that role. It is quite prolific in spreading via runners (rhizome roots), but it stays quite short, rarely growing larger than 2′. But the amount of plant material generated by Whorled Milkweed can feed an army of caterpillars. I’ve grown a large patch over the last few years and can share all that I’ve learned with you.

In this article:

What is Whorled Milkweed

Whorled Milkweed is a flowering perennial flower native to Eastern North America. Scientifically known as Asclepias verticillata, it will grow to about two feet tall by 0.5-1′ wide and bloom tons of white flowers for up to two months. As a milkweed, it serves as a host for Monarch Butterflies & attracts scores of other pollinators.

Of all the milkweeds, Whorled Milkweed is one of the shortest growing (similar to Butterfly Weed). But unlike Butterfly Weed, Whorled Milkweed can spread aggressively via rhizome root system.

In my own personal experience, from year 1 to 2, I had six small seedlings turn into a carpet of plants. Now, although an aggressive spreader, this patch of Whorled Milkweed attracted more Monarchs and Monarch caterpillars than I’ve ever seen. I found several chrysalis and even witnessed one Monarch butterfly emerge.

Native Range of Whorled Milkweed

Whorled Milkweed is native to most of North America, being present in most areas East of the Rocky Mountains. It is a pioneer species, establishing itself prior to being shaded out by other, taller Native Perennials. Whorled Milkweed is one of the most wide-spread milkweed species in North America.

Reference Table

Scientific NameAsclepias verticillata
Common Name(s)Whorled Milkweed,
Native Range, USDA ZoneContinental USA, East of Rocky Mountains. Hardiness zones 3-9
Bloom TimeSummer, July-September
Bloom Duration, Color4-8 weeks, White.
Height1-3′ (30 cm -90 cm)
Spacing / Spread1-2′ (30-60 cm)
Light RequirementsFull sun, partial shade
Soil TypesLoam, Sandy Loam, Silt, Clay Loam, Rocky soil
MoistureDry to medium conditions
Fauna Associations / Larval HostsMonarch Butterflies, numerous bee species, pollinating wasps, skippers, butterflies
Sources [1], [2], [3]

What are the pros and cons of Whorled Milkweed

Pros

A long bloom time

Whorled Milkweed will generally bloom for 2 months. Sometimes longer if you have a large patch. Any perennial that blooms that long is a plus.

Pollinators

There are many different pollinators that visit Whorled Milkweed. I regularly see honey bees, pollinating wasps, and many other bee species, skippers, and butterflies. Let me tell you, Whorled Milkweed is BUSY with pollinators.

Monarch Butterflies

A host of the endangered Monarch Butterfly, Whorled Milkweed will attract them one way or another. If you plant a few seedlings in year 1, you will have sooooo many plants via rhizomes in year two that you will have tons of caterpillars.

Seriously, in year 2 I had more caterpillars per plant than almost any other species of Milkweed I’ve ever grown. Now, this could have been influenced by some surrounding species of Liatris. But none the less, I had a ton of caterpillars – which is exactly the results I was looking for.

A tough plant

Whorled Milkweed will take little care to thrive. I planted 6 small seedlings in July or August of 2020, and in 2021 I had a CARPET of plants. I was amazed. And, these flowers experienced drought, moist conditions, and had no attention from me outside of a camera.

Cons

Aggressive Spreading

Whorled Milkweed has been one of the most aggressive plants I’ve ever grown. I’m not going to sugar coat anything. This plant spreads like mad. It’s like evolution has taught it that due to it’s short height it has to spread as much as possible when it can grow before it gets shaded out by taller plants.

New sprouts of Whorled Milkweed that spread via Rhizome Root, Spring.

Toxic

Whorled Milkweed, like all milkweeds is toxic to humans and mammals alike. It is only fatal in large quantities, but you need to be aware of the toxicity. [4]

A tough plant

While being a ‘tough’ plant can be a pro, it can also be a con. And for such a prolific spreading plant, the toughness of Whorled Milkweed is a con as much as a pro.

Not showy

The flowers of Whorled Milkweed are pretty, but they are not ‘showy’. So, growing this plant can be ecologically beneficial, but it isn’t so beautiful that you would win gardening awards. Don’t get me wrong, they look good – but not “Purple Coneflower good”.

Identification and Characteristics of Whorled Milkweed

Whorled Milkweed is a low growing Milkweed (6″-24″) with delicate whorled leaves that are quite soft. It can form a carpet of white ‘Milkweed Style’ flowers. It doesn’t tolerate taller competition well, so is more of a pioneering species. It is not likely to be found in well established prairies. [1]

Stalk

The round stalk of Whorled Milkweed is medium green to yellow green and unbranched except in the upper third of the stalk. There are vertical lines of tiny hairs present as well.

Stalk and leaves of Whorled Milkweed

Leaf

The leaves of Whorled Milkweed are whorled, or arrayed around the stalk in groups of 3-7. Individual leaves are linear in shape, 2-3″ (5-7.5 cm) long and about 1/8″ (3 mm) wide. The leaves are medium green to yellow-green. Leaves also have very tiny hairs on them.

Whorled Milkweed leaves turning yellow

During times of drought, the leaves of Whorled Milkweed may turn yellow. Just provide some supplemental water and the leaves should return to a normal green or green-yellow color.

Flower

Rounded clusters (umbels) of white, green-white flowers are on the upper third of the stalk, and are approximately 1-2″ (2.5-5 cm) diameter. There are generally 5-20 flowers per umbel.

Close up image of Whorled Milkweed flower

Individual flowers are white, green-white, or purple-tipped and approximately 1/4″ (6 mm) diameter and 3/8″ (10 mm) long, and of the general ‘Milkweed style’. A ‘milkweed-style‘ flower will have 5 petals, hoods, and sepals.

Seed pods opening on Whorled Milkweed

Whorled Milkweed will bloom for 4-8 weeks in Summer between July and September. After blooming, narrow erect pods (roughly 3.5″ long by 1/2″ wide) will form. Like other Milkweeds, the pods of Whorled Milkweed will be packed with small flat seeds attached to white feathers/hair.

Pods can be collected and seeds can be saved similar to other Milkweed species. Seeds of Whorled Milkweed can be saved and stored in a cool dry place for several years.

Root

The root system of Whorled Milkweed is fibrous and rhizomatous. The rhizomes will run far and produce numerous clones.

Natural Habitat of Whorled Milkweed

Whorled Milkweed can grow in a huge variety of places and conditions. But is most commonly found in ditches, roadsides, along railroads, and in drier locations where competition from taller plants isn’t significant. In prairies with average moisture Whorled Milkweed can be shaded out.

Grow and Care for Whorled Milkweed

Sunlight Requirements

Whorled Milkweed will grow best in full sun, which is at least six hours of direct sunlight per day. But it can grow in partial shade, which is 4 to 6 hours of direct sunlight per day.

Monarch Caterpillar feeding on Whorled Milkweed with Wild Sunflower in the background

Moisture Requirements

Whorled Milkweed grows best in medium-moist soil, or average moisture. It can tolerate drier conditions on slopes and is drought tolerant.

Soil Requirements

For soil preference, Whorled Milkweed is quite adaptable in that it will grow well in almost any soil. It can grow in sandy soil, rocky, clay-loam or loam.

Is Whorled Milkweed aggressive?

Whorled Milkweed will spread fast and can become aggressive and invasive in disturbed or open soil. I would not recommend it for a formal flower garden unless you gave it it’s own isolated bed, or significant measures were taken to control it’s spread.

The rhizome roots get to work quick, making multiple new clonal plants in just it’s second year. I planted six small plants, in the Summer of 2020 that grew to a carpet by 2021.

This is year 2 of six Whorled Milkweed plants…..it will spread.

How to control Whorled Milkweed

Due to it’s aggressive nature, Whorled Milkweed cannot be controlled by hand pulling unless one is willing to commit to a long battle. One needs to kill the root using a herbicide such as an general broad-leaf herbicide. Follow the label instructions, and keep an eye out for any ‘stragglers’.

How to Grow Whorled Milkweed from Seed

Whorled Milkweed seeds can be readily germinated after a period of cold moist stratification or via winter sowing. The planting depth should be very shallow, 1/16″ (1.5 mm).

Asclepias verticillata seed
Whorled Milkweed Seed

Process to grow Whorled Milkweed from seed in pots or containers

The following steps should be done after cold-stratifying Whorled Milkweed seeds for 30 days, or for planting seeds for Winter Sowing. If you are unfamiliar with Winter Sowing, you can read our illustrated guide here.

To grow Whorled Milkweed seed in containers, you must perform the following steps

  1. Fill a container with moist potting soil, leaving a 1/2″ gap at the top
  2. Press 3 to 5 seeds into the soil.
  3. Take another handful of potting soil, and sprinkle it on top of the container
  4. Place pots in a location where they will receive morning sun and afternoon shade
  5. Keep moist and wait for germination
asclepias verticillata seedling
Whorled Milkweed Seedlings

How to direct sow Whorled Milkweed seed

Direct sowing Whorled Milkweed seed is easy. You can direct sow on disturbed soil in Autumn through early Spring. Just scatter seed on disturbed, bare soil and then walk on the seed to ensure good contact. Seed will germinate in Spring.

Wildlife, Pests, and Diseases associated with Whorled Milkweed

Pollinators

The flowers of Whorled Milkweed produce significant amounts of nectar that attract numerous species of pollinators including butterflies, bees, pollinating wasps & flies, and skippers. The foliage is also a host of the Monarch Butterfly, and the caterpillars will feed on the foliage. [3]

Monarch Butterfly and Whorled Milkweed

Whorled Milkweed is good for the Monarch Butterfly as it produces significant biomass from it’s spreading nature, and is one of the latest blooming milkweed. I witnessed dozens of caterpillars feeding on the foliage.

Monarch Caterpillar feeding on Whorled Milkweed foliage

Pests

There are numerous insects besides the Monarch caterpillars that can feed on the foliage of Whorled Milkweed. The Milkweed Bug, Milkweed Leaf Beetle, and Yellow Milkweed Aphid all feed on the foliage or suck sap from the stalk.

Of these, the Yellow Milkweed Aphid is perhaps the most unsightly. But, they are not fatal to the plant, and are part of the ecosystem.

Oleander Aphids on Whorled Milkweed

Deer and rabbits

As a general rule, Deer and Rabbits avoid Whorled Milkweed as it is toxic and has a bitter taste. I have never noticed any damage on my plants from rabbits or deer.

Livestock and Toxicity off Whorled Milkweed

Whorled Milkweed is highly toxic to humans and animals alike. And livestock poisoning from grazing can happen. If you have livestock, take measures to ensure that Whorled Milkweed is not present when making hay or in grazing fields. [4]

Disease

Whorled Milkweed is generally unaffected by disease. But the leaves of Whorled Milkweed can turn yellow during times of drought.

Where you can buy Whorled Milkweed

Whorled Milkweed is not typically sold in nurseries, as it isn’t a typical ‘garden friendly’ plant. But it can be purchased at specialty nurseries that deal in Native Plants. You can find native plant nurseries near you on our interactive map.

Where to buy seeds

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

Uses of Whorled Milkweed

Garden Uses

Whorled Milkweed is not a good choice for formal flower gardens due to it’s spreading nature. You either have to give it it’s own bed, or use one of our methods to control the spread or rhizome producing plants.

But it can look nice as it’s own carpet of white flowers. Additionally it can be interspersed in a border garden, wildflower garden, or micro-prairie.

Companion Plants of Whorled Milkweed

If you want to grow Whorled Milkweed in it’s own bed or wildflower area, you should try to grow it with similar sized, or smaller plants. Some good candidates of flowers that can compete with Whorled Milkweed and share similar growing conditions would be the following:

Whorled Milkweed and Native American uses

There are 9 documented documented medicinal uses by four different tribes. Some examples include the following:

  • The roots were used as a stimulant, sudorific and as a snake bite remedy by the Choctaw
  • The plant was used by the Hopi as a gynecological aid
  • To treat throat problems
  • Roots were used to treat rashes by several tribes

Learn about other Milkweed Plants here

References:

[1] – McKenna, Duane D. Asclepias Verticillata and Roadways of the Upper Midwest: From Home on the Range to Life in the Fast Lane. Ann Arbor, MI: Michigan Publishing, University of Michigan Library, 2002.

[2] – Wilbur, Henry M. “Life history evolution in seven milkweeds of the genus Asclepias.” The Journal of Ecology (1976): 223-240.

[3] – Willson, Mary F., Robert I. Bertin, and Peter W. Price. “Nectar production and flower visitors of Asclepias verticillata.” American Midland Naturalist (1979): 23-35.

[4] – Glover, George Henry, Isaac Ernest Newson, and Wilfred William Robbins. A New Poisonous Plant: The Whorled Milkweed (Asclepias Verticillata). Vol. 246. Agricultural Experiment Station of the Agricultural College of Colorado, 1918.

[5] – Whorled Milkweed, North American Ethnobotany Database. Accessed 29DEC2021.

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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