7 Types of Milkweed You Can Plant in Arizona (AND One to Avoid!)
“What types of milkweed should I plant in my garden?”
This may seem like a crazy question if you’re just getting started with native gardening. Why would you want to plant a weed?!
But milkweed isn’t a weed at all. Instead, it’s a flowering plant that attracts butterflies (think Monarchs), native bees, and other pollinating insects, which is an excellent thing!
This article will give you information about common types of milkweed in your area and which ones will be best for your garden. And, keep reading to the end to learn about a kind of milkweed you want to avoid!
7 Types of Milkweed in Arizona:
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#1. Whorled Milkweed
- Asclepias verticillata
Growing Information:
- USDA Hardiness Zone: 3-10
- Life Cycle: Perennial
- Approximate Mature Size: 1 to 3 feet
- Bloom Time: May to September
Whorled Milkweed is the most broadly distributed milkweed species in Arizona.
This unique perennial is sometimes overlooked by gardeners who want to plant milkweed. Compared to other varieties, it has a narrow stem and spiky leaves arranged in a spiral pattern. When not in bloom, it easily blends in among grasses.
It blooms from May to September, forming flat-topped clusters of small greenish-white flowers on the end of each stem. The flowers attract various insects, including bees, wasps, butterflies, skippers, beetles, and flies.
Whorled Milkweed is still a welcome host plant for Monarch Butterfly caterpillars despite its unique appearance. Since this species is one of the last milkweeds to die back in the fall, it’s a great late-season host for Monarchs preparing to migrate south!
This delicate-looking wildflower can easily grow from seed, but it may not flower the first year. It can be grown in full sun or partial shade. Whorled Milkweed thrives in various habitats, including fields, pastures, roadsides, dry prairies, dry slopes, woodlands, and meadows. Unfortunately, it’s highly poisonous to livestock and is considered a nuisance weed in agricultural areas.
It grows best in dry soil of various types, including sandy, rocky, and clay soils. It can also be grown in moist, average garden soil. Keep in mind that it is an aggressive spreader by seeds and underground rhizomes, so you may not want to choose this milkweed if you have a limited area for gardening.
#2. Desert Milkweed
- Asclepias erosa
Growing Information:
- USDA Hardiness Zone: 4-11
- Life Cycle: Perennial
- Approximate Mature Size: 1.5 to 4 feet
- Bloom Time: May to July
As the name suggests, this species is commonly found in desert regions. Desert Milkweed often grows on dry slopes and washes. The stems are yellow to green and broader at the base.
Identifying this species can be difficult as there’s some variation in the leaves. They grow in pairs on the stem and may be completely smooth or densely covered in cream-colored hair. They’re generally dull grayish or pale to dark green. Desert Milkweed blooms from May to July, forming rounded umbels or clusters of about 20 small flowers atop the stems. The flowers are white, cream, or yellow.
Desert Milkweed is quite adaptable and can be grown from seed in many home gardens. It needs well-drained sandy soils in areas with low organic matter. It should be planted in full sun. Like other milkweeds, its large taproot gives it excellent drought tolerance.
This species is a host plant for the Monarch Butterfly, Queen Butterfly, Clio Tiger Moth, and Euchaetes Zella Moth. The blooms also attract a variety of pollinators, including native bees.
#3. Butterfly Weed
- Asclepias tuberosa
Growing Information:
- USDA Hardiness Zone: 3-9
- Life Cycle: Perennial
- Approximate Mature Size: 2 to 3 feet
- Bloom Time: May to September
Butterfly Weed is a showy member of the milkweed family. Sometimes called Orange Milkweed, this perennial wildflower features large flat-topped clusters of tiny flowers that grow 2 to 5 inches across. The blooms are brilliant orange or yellow.
Interestingly, its dark green leaves and stems don’t produce the same milky sap as other species of milkweed in Arizona.
Butterfly Weed is an excellent choice for gardens and or wildflower meadows. The beautiful flowers are fragrant and are ideal for cut flower arrangements. They also attract native bees, butterflies, and honeybees to your garden. Butterfly Weed is also a host plant for Monarch, Gray Hairstreak, and Queen butterfly caterpillars.
This native flower is a great low-maintenance choice for the home gardener. Butterfly Weed’s deep taproots mean you’ll never need to water it once it’s established. In addition, this plant is highly drought tolerant and thrives in full sun. Butterfly Weed also does fine without any fertilization but grows best in rocky or sandy soil.
Unlike Common Milkweed, this species doesn’t transplant well and should be started from seed.
#4. Green Comet Milkweed
- Asclepias viridiflora
Growing Information:
- USDA Hardiness Zone: 3-10
- Life Cycle: Perennial
- Approximate Mature Size: 1.5 to 2 feet
- Bloom Time: June to September
Green Comet Milkweed flower clusters form in the pocket created by the upper leaves. They’re made up of 20 to 80 small, pale green flowers. Interestingly, the yellowish-green leaves of this species vary in shape depending upon their habitat. Plants from moist sites tend to have rounder leaves, while plants from dry sites have long, narrow leaves.
In the wild, this species is often found on shaded roadsides, savannas, and prairies with moist to dry soil. In the garden, you can grow Green Comet Milkweed from seeds. It grows best in light to moderate shade but will tolerate full sun. Medium-dry to dry soil is best. Green Comet Milkweed doesn’t need rich soil and will tolerate sandy or rocky soil with low organic matter.
This species is a good choice for low-maintenance gardens as its long taproot allows it to tolerate drought well. Unlike many other milkweeds, this species is easy to prevent from spreading. It doesn’t form the large colonies typical to other milkweeds, so it’s an excellent option for smaller gardens!
The Green Comet Milkweed’s copious nectar and sweet fragrance attract many pollinators, including honeybees, native bees, and butterflies. It’s also a host plant for Monarch Butterflies, though it can be more challenging for monarchs to find because of its scarcity and preference for partial shade.
#5. Showy Milkweed
- Asclepias speciosa
Growing Information:
- USDA Hardiness Zone: 3-8
- Life Cycle: Perennial
- Approximate Mature Size: 1.5 to 3 feet; occasionally up to 6 feet
- Bloom Time: May to September
As the name suggests, Showy Milkweed features flashy pink and white umbels or clusters of small flowers. The flowers are fragrant, and individual flowers look a bit like crowns. In ideal conditions, Showy Milkweed may grow as tall as 6 feet!
As a garden plant, Showy Milkweed has the benefit of being a less aggressive spreader than most other milkweed varieties in Arizona. It can be grown easily from seed or the cuttings of an existing plant. It’s very drought tolerant and can be grown in a wide range of soils.
Like other milkweeds, Showy Milkweed attracts native insects and Monarch Butterflies to your yard or garden. Monarchs will visit the flowers for nectar and lay eggs on the plants, which are host plants for the Monarch caterpillars. It will also attract beautiful Queen and Viceroy butterflies to your property!
#6. Antelope Horns
- Asclepias asperula
Growing Information:
- USDA Hardiness Zone: 5-9
- Life Cycle: Perennial
- Approximate Mature Size: 1 to 2 feet
- Bloom Time: March to October
Antelope Horns, also known as spider flower, tends to sprawl toward the ground instead of standing upright. The stems of this milkweed are green-tinged with maroon and densely covered in tiny hairs.
This milkweed species gets its name from its relatively distinctive seed pods. The curved, upturned pods are thought to resemble antelope horns. When viewed from a distance, these plants resemble a field of antelope. The leaves are narrow, up to 8 inches long, and fold inward along the middle vein. Look for the whitish-green or purple flower clusters during its long blooming season.
Like other milkweeds, Antelope Horns’ flowers attract a variety of pollinators. Large native bee species regularly visit the blooms. The plants are also hosts for Monarch, Soldier, and Queen butterfly caterpillars.
This species is relatively easy to grow from seed. Antelope Horns need full sun to thrive and prefer sandy or rocky soil with little organic matter. It’s a great low-maintenance choice, and it thrives without any fertilization and little watering due to its large taproot.
#7. Zizotes Milkweed
- Asclepias oenotheroides
Growing Information:
- USDA Hardiness Zone: 7-9
- Life Cycle: Perennial
- Approximate Mature Size: 1 to 1.5 feet
- Bloom Time: March to September
This species is also known simply as Zizotes or “hierba de zizotes.” It’s the least hardy species of milkweed in Arizona and requires a warm climate to survive.
The greenish-white flowers of the Zizotes Milkweed are notable for their long, slender hoods, which extend up and over the central column making this species easy to identify in bloom. The individual flowers look like tiny champagne flutes!
This species can grow in the wild in prairies, fields, desert grasslands, pinyon-juniper woodlands, and ditches with sandy or rocky soil. At home gardens, Zizotes Milkweed can be grown from seed. However, this species does not tolerate shade and should be planted in full sun with dry, sandy soil.
This milkweed species is especially notable because it can survive periodic droughts and even occasional mowing. As a result, it’s an easy way to incorporate pollinator-friendly, native plants into your landscape. In addition, like other milkweeds, this species is an important host plant for the caterpillars of Monarchs.
Tropical Milkweed
- Asclepias curassavica
Growing Information:
- USDA Hardiness Zone: 8-11
- Life Cycle: Perennial
- Approximate Mature Size: 3 to 4 feet
- Bloom Time: March to November in temperate climates, year-round in tropical climates.
This non-native milkweed plant has become popular in recent years because of its flowers’ bright red coloring and how easy it is to plant and maintain.
Unfortunately, Tropical Milkweed planted in Arizona may do more harm than good.
It carries a parasite of Monarch Butterflies called Ophryocystis elektroscirrha, or OE, which can cause defects in the wings of Monarchs. Since it doesn’t die back and can bloom late, the plant itself may also confuse Monarchs by signaling a breeding season when it’s time to migrate.
To ensure you’re planting milkweed that will help your local ecosystem and attract native pollinators, always choose a native species!
Marketers of Tropical Milkweed seeds will use the names Mexican Milkweed, Bloodflower, Mexican Butterfly Weed, Mexican Orange Milkweed, and Semi-Tropical Milkweed. Steer clear of all of these!
Are you looking for more information on milkweed in Arizona?
Check out this guide!
Do you have milkweed in your garden?
What’s your favorite thing about this plant? Leave a comment below!