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12 Irresistible Allegheny County, PA Milkweeds (Asclepias spp.) to Grow for Butterflies

Make your Allegheny County butterfly garden into a buffet for butterflies by getting rid of the chemicals and planting a nectar rich haven. A good start are milkweeds (Asclepias spp.), which do double duty as a host for monarch butterflies and a nectar source many other insects. Milkweed hosts the monarch butterfly caterpillars and provides the cardenolides that gives it a bad taste to predators when it is an adult. Dive into the article to find out about the plant hardiness zones in Allegheny County, and the planting requirements needed for milkweeds in the county.

Location of Allegheny County, Pennsylvania

Allegheny county in red on a map of Pennsylvania.
Map of Pennsylvania with Allegheny County Highlighted in RedDavid Benbennick, Public domain, via Wikimedia Commons

Allegheny County, PA is located in southwestern Pennsylvania. The confluence of the Monongahela and Allegheny Rivers, forming the Ohio River is located in the county. Pittsburgh is the major city in the county.

USDA Plant Hardiness Zones in Allegheny County, Pennsylvania

USDA plant hardiness zone map (2023) for the state of Pennsylvania.
2023 USDA Plant Hardiness Zone Map for Pennsylvana — USDA Public Domain

Most of Allegheny County, Pennsylvania is located in plant hardiness zone 6b, with a few scattered areas along the Ohio River and Monongahela Rivers in zone 7a. Generally when selecting plants you will want to get those that can handle temperatures as cold as -50F to be sure they will survive.

Butterflies in Allegheny County, Pennsylvania that are Hosted by Milkweeds (Asclepias spp.)

Monarch (Danaus plexippus) caterpillar on leaf.
Monarch Butterfly Caterpillar — Maria L. Evans, CC BY-SA 4.0, via Wikimedia Commons

Monarch Butterfly (Danaus plexippus)

List of Native or Nearly Native Allegheny County, PA Milkweeds (Asclepias spp.)

1. Clasping Milkweed (Asclepias amplexicaulis), a Milkweed for Sandy Soils

Transform your yard into a butterfly haven with this blunt-leaved milkweed that hosts the monarch butterfly and packs a punch in attracting other butterflies. Your patch of paradise can be turned into a meadow of flitting insects enjoying the delights of your planted buffet.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-9 and requires full sun to part-shade and moist to dry sandy soils. Seeds of clasping milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Plant of clasping milkweed (Asclepias amplexicaulis) with pink flowers in a wooded area.
Clasping Milkweed (Asclepias amplexicaulis) — Mason Brock (Masebrock), Public domain, via Wikimedia Commons
Pinkish flowers of clasping milkweed (Asclepias amplexicaulis) in a field, a Raleigh milkweed.
Flowers of Clasping Milkweed (Asclepias amplexicaulis) — cassi saari, CC BY-SA 4.0, via Wikimedia Commons
Reddish-pink flowers of clasping milkweed (Asclepias amplexicaulis) in a field.
Flowers of Clasping Milkweed — “Asclepias amplexicaulis – Clasping Milkweed” by FritzFlohrReynolds is licensed under CC BY-SA 2.0.

2. Poke Milkweed (Asclepias exaltata), a Milkweed for Shade and Moist Soils

Poke Milkweed (Ascelpias exaltata): Poke milkweed is located throughout Pennsylvania (Kartesz 2015) and is native to Allegheny County. In the wild, poke milkweed grows in moist woods, roadsides, and the edges of woods. Growing from 2 to 6 feet tall it is one of the taller milkweeds in Pennsylvania and has flowers that are white to green with accents of rose, purple, or blue. Blooming occurs from May to August.

Host the monarch butterfly and beckon other butterflies with this gentle giant of a milkweed that has fragrant lavender-tinged blooms. Towering over other plants and joining other tall plants such as joe-pye-weed (Eutrochium spp.) and ironweed (Vernonia spp.), you can turn your garden into a nectar powerhouse.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-9 and requires part-shade to full shade and moist soil. For shade gardens, this is a choice milkweed. Seeds of poke milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Greenish-white flowers of poke milkweed (Asclepias exaltata) in a wooded area.
Flowers of Poke Milkweed (Asclepias exaltata) — Dendroica cerulea, CC BY 2.0, via Wikimedia Commons
Plant of poke milkweed with white flowers in a wooded habitat.
Poke Milkweed in a Wooded Area — “Asclepias exaltata” by kevinliam is marked with CC0 1.0.
White flowers of poke milkweed (Asclepias exaltata) in a wooded area.
Poke Milkweed (Asclepias exaltata) — homeredwardprice, CC BY 2.0, via Wikimedia Commons

3. Swamp Milkweed (Asclepias incarnata), a Milkweed for Moist Soils

This milkweed prefers wet soils, but it is not just for mud. In your garden this thin-stalked plant with a rosy-blush can accent your nectar buffet and provide sustenance for monarch butterflies. This plant makes a nice contrast and splash of color when planted with yellow and white flowered plants.

In your Allegheny County butterfly garden, swamp milkweed is overall hardy in zones 3-9. However, in the horticultural trade you will likely get subsp. incarnata, which is hardy in zones 3-9. This milkweed requires full sun to partial shade and well-drained soil. Seeds of swamp milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Pink flowers of swamp milkweed (Asclepias incarnata) from Pennsylvania.
Flowers of Swamp Milkweed (Asclepias incarnata) — Cbaile19, CC0, via Wikimedia Commons
Swamp milkweed (Asclepias incarnata) 'Ice Ballet' cultivar.
‘Ice Ballet’ cultivar of Swamp Milkweed (Asclepias incarnata) — Photo by and (c)2009 Derek Ramsey (Ram-Man), GFDL 1.2, via Wikimedia Commons
Follicles (fruits) of swamp milkweed (Asclepias incarnata) in a garden.
Follicles — “Swamp milkweed, rose milkweed, asclepias incarnata, new England native garden” by sapienssolutions is licensed under CC BY 2.0.

4. Purple Milkweed (Asclepias purpurascens), a Milkweed for Moist Soils

Purple Milkweed (Asclepias purpurascens): Purple milkweed is scattered around Pennsylvania but is generally in the southern counties (Kartesz 2015). This milkweed is native to Allegheny County. In the wild, purple milkweed grows in swamps, woodlands, meadows, and roadsides. Growing up to 6 feet tall, it is one of the larger milkweeds in Pennsylvania, and has flowers, as the name suggests that are generally purple, but can range from rose to pink, or may start out pink and mature to purple.

This milkweed is another gentle giant of a milkweed that likes shade. If you have a shaded garden, this milkweed makes a great choice and you can create a place for monarch butterfly caterpillars to thrive and nectar for other insects. Turn your shaded spot in a fluttering place of magic and flying harmony.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-8 and generally requires part-shade, but can handle full sun if needed. Soils should be moist and well-drained, but dry soil can be tolerated. Seeds of purple milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Close-up of pinkish-purple flowers of purple milkweed (Asclepias purpurascens).
Flower cluster of Purple Milkweed (Asclepias purpurascens) — Steepcone, Public domain, via Wikimedia Commons
Plants of purple milkweed (Asclepias purpurascens).
Purple Milkweed (Asclepias purpurascens) — peganum from Henfield, England, CC BY-SA 2.0, via Wikimedia Commons
Plant of purple milkweed (Asclepias purpurascens) with purple flowers.
Purple Milkweed with Purple Flowers — Asclepias purpurascens L. observed in United States of America by Jim Bowhay (licensed under CC0 1.0)

5. Four-leaf Milkweed (Asclepias quadrifolia), a Milkweed for Dry Rocky Soils

Four-leaf Milkweed (Asclepias quadrifolia): Four-leaf milkweed is located throughout Pennsylvania (Kartesz 2015) and is native to Allegheny County as well. In the wild, four-leaf milkweed grows in open areas such as roadsides, pastures, and prairies that have some disturbance. Growing from 1 to 3 feet tall, the flowers range from white to pink in color and bloom from April to July.

If you have a combination of full sun or part-shade, this plant is the key to turning your yard into buffet of munching caterpillars. Later you will have a winged ballet and fluttering fandago of monarchs and swallowtails flying from plant to plant in the sun and shade.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 5-8 and prefers places where it can enjoy full sun or part-shade and dry rocky soils.

Plant of four-leaf milkweed (Asclepias quadrifolia) with whitish flowers.
Four-leaf Milkweed (Asclepias quadrifolia) — Photo 18324078, no rights reserved, uploaded by Prairie Voyageur
Pinkish flowers of four-leaf milkweed (Asclepias quadrifolia).
Flowers of Four-leaf Milkweed (Asclepias quadrifolia) — User:Halpaugh, CC BY-SA 3.0, via Wikimedia Commons
Plant of four-leaf milkweed (Asclepias quadrifolia) with white flowers.
Four-leaf Milkweed (Asclepias quadrifolia) — Eric Hunt, CC BY-SA 4.0, via Wikimedia Commons

6. Showy Milkweed (Asclepias speciosa), a Milkweed for Medium to Dry Soils

Showy Milkweed (Asclepias speciosa): Showy milkweed is native to the western United States, but is widely planted in butterfly gardens elsewhere. It is considered to be adventive in one county in Ohio (Kartesz 2015) and can handle the plant hardiness zone in Allegheny County. In the wild, showy milkweed grows in open areas with full sun such as roadsides, pastures, and fields. Growing from 1 to 3 feet tall, this plant has flowers that are purple, pink to white and bloom from May to June.

Imagine the soft brushstrokes of of pink and purple having star-shaped blooms acting as a beacon for weary monarchs and playground for bees. Transform your sunny location into a scent filled extravagnaza and while watching your guests delight in the sun kissed nectar.

In your Allegheny County butterfly garden, showy milkweed is hardy in zones 3-9 and requires full sun with medium to dry well-drained soil. Seeds of showy milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Pinkish-white flowers of showy milkweed (Asclepias speciosa).
Asclepias speciosa Torr. observed in Canada by markeambard (licensed under CC0 1.0)
Pinkish flowers of showy milkweed (Asclepias speciosa).
Flowers of Showy Milkweed (Asclepias speciosa) — Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0, via Wikimedia Commons
Follicle of showy milkweed (Asclepias speciosa).
Showy Milkweed (Asclepias speciosa) Follicle — John Rusk from Berkeley, CA, United States of America, CC BY 2.0, via Wikimedia Commons

7. Sullivant’s Milkweed (Asclepias sullivantii), a Milkweed for Medium to Dry Soils

Sullivant’s Milkweed (Asclepias sullivantii): Sullivant’s milkweed is native generally to the midwestern United States and ranges as close as central Ohio to Allegheny County. While not native to the county, it can grow in the plant hardiness zone, though climate change warming render this time short. In the wild, sullivant’s milkweed grows in open areas with full sun such as prairies, meadows, roadsides, and railroads. It is associated with tall grass prairies (Minnesota DNR). Growing from 2 to 5 feet tall, the pink to purplish flowers bloom from June to July.

Also called the prairie milkweed, this milkweed does not desire attention, and has a pink cluster of flowers that tower over the waves of grass. In your sunny drenched garden this plant can nourish milkweed caterpillars, provide nectar to the plethora of guests, and surround you with a sweet scent.

In your Allegheny County butterfly garden, Sullivant’s milkweed is hardy in zones 3-7 and requires full sun medium to dry sandy soil. Seeds of Sullivant’s milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Plant of sullivant's milkweed (Asclepias sullivantii) with pink flowers.
Asclepias sullivantii Engelm. ex A.Gray observed in United States of America by Nancy Navarre (licensed under CC0 1.0)
Brown follicle (fruit) of sullivant's milkweed (Asclepias sullivantii).
Asclepias sullivantii Engelm. ex A.Gray observed in United States of America by Nancy Navarre (licensed under CC0 1.0)
Plant of sullivant's milkweed (Asclepias sullivantii) in a field.
Asclepias sullivantii Engelm. ex A.Gray observed in United States of America by samk (licensed under CC0 1.0)

8. Common Milkweed (Asclepias syriaca), a Milkweed for all Soils

Common Milkweed (Asclepias syriaca): Common milkweed is located throughout Pennsylvania (Kartesz 2015) and is native in Allegheny County. This milkweed is found in open areas such as fields, pastures, and roadsides, where it can receive full sun. Growing up to 6 feet tall, this milkweed has flowers range from pink, greenish-purple, greenish-white, to white and blooms from June to August.

An inhabitant of fields and roadsides, this milkweed is leafy powerhouse with large flowers and a strong scent. Handling nearly any kind of garden condition, this milkweed provides ample foraging for monarchs and nectar for many. This plant can form the perfect compliment when joined with purple coneflower (Echinacea purpurea) and other butterfly garden plants, making a colorful tapestry.

In your Allegheny County butterfly garden, common milkweed is hardy in zones 3-9 and requires full sun to part-shade and any type of soil. Seeds of common milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Flowers of Common Milkweed (Asclepias syriaca), a North Carolina milkweed.
Pink Flowers of Common Milkweed in McMullen House Garden — Robert Coxe, Image
Plant of common milkweed (Asclepias syriaca) with pink flowers.
Common Milkweed (Asclepias syriaca) — Cbaile19, CC0, via Wikimedia Commons
Common milkweed (Asclepias syriaca) with eastern tiger swallowtail.
Eastern Tiger Swallowtail on Common Milkweed — Author Image

9. Butterfly Weed (Asclepias tuberosa), a Milkweed for all Soils

Butterfly Weed (Asclepias tuberosa): Butterfly weed is one of the most common for butterfly gardeners on the east coast of the United States. In Pennsylvania, subspecies interior and tuberosa are both native. Both subspecies essentially occur throughout the state, though subsp. interior is more scattered in distribution. In Allegheny County, subsp. tuberosa is native, while subsp. interior is native to the north. In the wild, butterfly weed grows in open areas with full sun such as fields, roadsides, and open woods. Growing from 1 to 3 feet tall, it has characteristically orange flowers that bloom throughout the summer and sometimes into the autumn.

If you need a hint of orange in a sea of white and pink milkweeds, this plant is for you. This orange milkweed is one of the few of this color and sustains the monarch butterfly is a valuable nectar for other insects. Imagine a fluttering calcophony of yellow, black, and orange on orange flowers. If you have a sunny garden or want to grow a milkweed in a container this plant is for you.

In your Allegheny County butterfly garden, this milkweed is hardy from zones 3-9 and requires full sun in any type of soil condition. This is one of two milkweeds in North America that does not have milky sap. Seeds of butterfly weed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Orange flowers of butterfly weed (Asclepias tuberosa).
Butterfly Weed with Orange Flowers — Robert Coxe, Image
Monarch butterfly on butterfly weed (Asclepias tuberosa).
Butterfly Weed with Monarch Butterfly — U. S. Fish and Wildlife Service – Northeast Region, Public domain, via Wikimedia Commons
Follicles of butterfly weed showing seeds.
Butterfly Weed Follicles — User:SB_Johnny, CC BY-SA 3.0, via Wikimedia Commons

10. Red-ring Milkweed (Asclepias variegata), a Milkweed for Dry Sandy Soils

Red-Ring Milkweed (Asclepias variegata): Red-ring milkweed is considered to be rare and is located in the eastern half Pennsylvania (Kartesz 2015). While not native in Allegheny County and rare, this species could handle the plant hardiness zone of the county. In the wild, red-ring milkweed grows in open disturbed areas such as thickets and roadsides. Growing from 1 to 4 feet tall, it has white colored flowers with a ring of purple to red at the base. The flowers bloom from May to July.

This milkweed, that is considered to be rare in Pennsylvania, lives in places where there is filtered light. The small balls of white can provide a textural contrast to the pinks of other milkweeds in your garden. In addition, like the butterfly weed, this plant is small and can be grown in a container for those with small gardens or patios.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-9 and prefers part-sun to light-shade and dry sandy or rocky soils. Seeds of red-ring milkweed can be purchased in the McMullen House Bed & Breakfast Garden Shop.

Close-up of white flowers of red ring milkweed (Asclepias variegata).
Red-ring Milkweed with White Flowers — Masebrock, Public domain, via Wikimedia Commons
Plant of red ring milkweed (Asclepias variegata) in a wooded area.
Red-ring Milkweed in a Wooded Area — “Asclepias variegata” by coatlicue is marked with CC0 1.0.
White flower clusters of red ring milkweed (Asclepias variegata).
Close-up of White Flowers — “Asclepias variegata” by coatlicue is marked with CC0 1.0.

11. Whorled Milkweed (Asclepias verticillata), a Milkweed for Medium to Dry Soil

Whorled Milkweed (Asclepias verticillata): Whorled milkweed is found in the central and eastern counties of the state (Kartesz 2015). While not native to Allegheny County, this species can grow in the hardiness zone of the county. In the wild, whorled milkweed grows in open areas such as meadows and fields, where it can take advantage of full sun. Growing from 1 to 3 feet tall, it has green to white flowers that bloom from May to September.

Another species providing textural appeal is the whorled milkweed. Another small milkweed, it provides nourishment for monarch caterpillars and nectar for other butterflies and bees. The overall look of the plant blends in with the swaying grasses in your garden.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-9 and requires full sun to part-shade with medium to dry soil. Seeds of whorled milkweed can be purchased at the McMullen House Bed & Breakfast Garden Shop.

Close-up of white flowers of whorled milkweed (Asclepias verticillata).
Flowers of Whorled Milkweed (Asclepias verticillata) — Joshua Mayer (wackybadger), CC BY-SA 2.0, via Wikimedia Commons
Leaves of whorled milkweed (Asclepias verticillata).
Whorled Milkweed (Asclepias verticillata) Leaves — Frank Mayfield (gmayfield10), CC BY-SA 2.0, via Wikimedia Commons
White flowers of whorled milkweed (Asclepias verticillata) in an open area.
Flowers of Whorled Milkweed (Asclepias verticillata) — Mason Brock (Masebrock), Public domain, via Wikimedia Commons

12. Green Comet Milkweed (Asclepias viridiflora), a Milkweed for Medium to Dry Sandy Soils

Green Comet Milkweed (Asclepias viridiflora): Green comet milkweed is scattered around Pennsylvania, but is generally in the central and southern counties (Kartesz 2015). It is native to Allegheny County. In the wild, green comet milkweed grows in open areas such as meadows and field where there is full sun. Growing up to 3 feet tall, the flowers, which bloom from June to August, begin as a green color but age to become yellow with a purple tinge.

This milkweed can add another color to your garden tapestry. The green flower color helps them to blend in with the leaves saving them from herbivores that would eat them. If you need a medium sized milkweed that can handle a variety of habitats, this milkweed is for you.

In your Allegheny County butterfly garden, this milkweed is hardy in zones 3-9 and requires full sun to part-shade with medium to dry sandy soil. Seeds of green comet milkweed can be purchased at the McMullen House Bed & Breakfast Garden Shop.

Green flower cluster of green comet milkweed (Asclepias viridiflora).
Flowers of Green Comet Milkweed — Patrick Alexander from Las Cruces, NM, CC0, via Wikimedia Commons
Plant of green comet milkweed (Asclepias viridiflora).
Green Comet Milkweed (Asclepias viridiflora) — Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0, via Wikimedia Commons
Leaves of green comet milkweed (Asclepias viridiflora).
Leaves of Green Comet Milkweed — Patrick Alexander from Las Cruces, NM, CC0, via Wikimedia Commons

When selecting plants for your Allegheny County butterfly garden, make sure they grow in your zone and habitat.

Books where you can find out more about Monarchs and Butterfly Gardening in Allegheny County, PA

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References

  • Kartesz, J.T. The Biota of North America Program (BONAP). 2015. Taxonomic Data Center. Link to website. Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]
  • Urguhart, Frederick Albert, Norah Roden Urguhart, and Francis Munger. 1968. Population of Danaus plexippus in Southern California. Journal of Research on the Lepidoptera 7(4): 169-181.
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Robert Coxe

Robert Coxe

Robert Coxe is a professional ecologist and botanist who has worked as the State Ecologist of Delaware and as an ecologist for the Western Pennsylvania Conservancy. He is also a former Past-President of the Pennsylvania Academy of Science. He currently is an innkeeper at McMullen House Bed & Breakfast LLC and a web designer and owner for Silphium Design LLC.