Arizona milkweed is an attractive, native perennial that’s an important host plant for queen and monarch butterflies. Here’s everything you need to know about planting and taking care of this butterfly magnet.
Arizona milkweed (Asclepias angustifolia) is a perennial flowering plant native to parts of Arizona and Mexico. It has a wispy, fern-like appearance.
Slender bright green leaves topped with clusters of white flowers tinged with pink or purple spring through summer make it a lovely addition to any butterfly garden.
This Arizona native is not found in the desert but rather in riparian woodlands, mountains, and canyons. Consequently, it needs more shade and water than most cultivated native plants.
I’ve always found it to be evergreen when grown in Tucson gardens, but it can lose its leaves when grown at higher elevations.
While Arizona milkweed is undoubtedly an attractive plant, it’s mainly grown for being butterfly-friendly.
Milkweed leaves are a crucial food source for the larval stage of the queen and monarch butterflies, while the flower nectar is an important food source for butterflies and many other insect pollinators including bees, wasps, and moths.
Why I Like This Plant
- Desert native essential for Monarch and Queen butterflies
- Low-maintenance plant that looks good all year
- Delicately beautiful white and pink-tinged blossoms
- Attractive fern-like foliage
- Low maintenance
Things to Watch Out
While many people love the idea of planting Arizona milkweed because it is butterfly-friendly, be aware that it attracts insects of all kinds, including some you might not want to see in your yard, especially aphids.
Aphids rarely harm a milkweed plant and they, in turn, attract beneficial insects such as ladybugs and green lacewings.
But if the thought of letting aphids co-exist freaks you out, Arizona milkweed is not a good choice for you.
You may have heard that you can remove aphids naturally by shooting them with a jet spray of water from your hose but this will not solve your aphid problem because you’ll also blast away the good bugs that keep them under control. The aphids will come back faster than the beneficial bugs. The end result will be more, not fewer, aphids.
Like all milkweeds, Arizona milkweed is toxic to dogs, cats, horses, and livestock.
Milkweed is potentially dangerous to humans as well as animals. The sap can cause skin and eye irritation. If ingested, it can cause serious digestive and cardiac issues.
Optimal Growing Conditions
If you’re thinking of adding an Arizona milkweed to your garden, you need to find a suitable place that will keep your plant healthy and looking good… while minimizing maintenance for you.
Here are the key factors to keep in mind.
Temperature
Arizona milkweed should be grown in USDA Hardiness Zones 8 – 10. It is tolerant of heat and cold-hardy down to 10℉.
Sun Exposure
Arizona milkweed will tolerate full sun, but since it naturally grows in canyons, it prefers partial shade. Ideally, plant it where it will be sheltered from the hottest afternoon sun such as on the east side of your house or in dappled shade.
Size and Growth Rate
Arizona milkweed is considered a moderate grower which will grow faster with more water. A typical specimen will reach a size of 3’ wide by 3’ tall when mature.
Soil
Arizona milkweed grows best in either clay or silty soils.
Other Location Considerations
Arizona milkweed should be kept away from children and pets due to its toxicity. It should not be planted where it can easily be brushed against due to its irritating sap.
Arizona Milkweed:
The Essentials
| Common Name | Arizona milkweed |
| Scientific Name | Asclepias angustifolia |
| Origin | Arizona, Mexico |
| Plant Type | Semi-deciduous perennial |
| USDA Zones | Zones 8 – 10 |
| Cold Hardy | To 10℉ |
| Flower Color | White with pink tinge |
| Flower Season | Spring, summer |
| Mature Size | 3′ high x 3’ wide |
| Growth Rate | Moderate |
| Sun Tolerance | Part shade |
| Water Needs | Moderate |
| Pests & Diseases | Aphids, root rot |
| Toxicity | Toxic to people, pets, livestock |
| Wildlife | Attracts butterflies, bees, hummingbirds Food source for butterfly larva Deer, rabbit resistant |
How to Plant
The rule of thumb when planting any milkweed in the desert is to dig a hole twice as wide as the root ball but no deeper.
Plant slightly higher than ground level, allowing room for some settling and mulch. Amending the soil is not recommended. Counterintuitively, backfilling with the same native soil you just dug up helps your plant develop a stronger root system.
When to Plant
The best time to plant milkweed is in the fall. This gives it three seasons to grow roots and get established before the following summer.
The second best time is in spring, the earlier the better. This still gives your plant time to get established before the intense heat of June arrives.
How to Care for Arizona Milkweed
Whether you’ve recently planted an Arizona milkweed or have an existing one in your yard, here’s how to take care of it to keep it healthy and looking its best.
How to Water
Once you’ve got your milkweed planted, watering is your most immediate concern. The Desert Botanical Garden in Phoenix recommends watering milkweeds deeply every day for the first week to help the roots get established.
After that, follow Pima County’s schedule for watering. The second week water every every 3 – 4 days. After that, water once a week in spring and fall, every two weeks in winter, and twice a week in summer.
While Arizona milkweed is a native, it’s not a desert plant
and so needs more watering than most other native plants.
Should You Fertilize?
Don’t fertilize Arizona milkweed. It’s well-adapted to grow in native soil. Fertilizing can cause this plant to flower less, not more.
How to Prune
Arizona milkweed maintains a naturally attractive form and doesn’t need pruning. However, if it’s getting leggy or too big for its spot, you can trim in the late fall. But wait until seed pods have formed and released their seeds to give them a chance to reseed.
An Abundance of Milkweeds Grow in the Desert Southwest
The common name Arizona milkweed suggests that it is found mainly (or only) in Arizona. While there are small pockets growing naturally in Arizona, the majority of native populations are found in Mexico.
Arizona milkweed is not the only native milkweed to grow in Arizona — the general consensus is that 29 native species grow in Arizona.
And of the 76 native milkweeds that grow in the continental US, 41 can be found in the southwest.
If you live in the desert southwest and want to diversify your butterfly garden, here’s a list of the milkweed species commercially available:
- Spider Milkweed, Antelope Horns (Asclepias asperula)
- Woollypod Milkweed (Asclepias eriocarpa)
- Giant Sand Milkweed (Asclepias erosa)
- Narrowleaf Milkweed (Asclepias fascicularis)
- Swamp Milkweed (Asclepias incarnata)
- Slim milkweed (Asclepias linearis)
- Showy Milkweed (Asclepias speciosa)
- Desert Milkweed, Rush Milkweed (Asclepias subulata)
- Horsetail milkweed (Asclepias subverticillata)
- Butterflyweed (Asclepias tuberosa spp. interior)
Did you enjoy this article?
Sign up for our weekly newsletter
where you’ll find more great info on creating &
maintaining a beautiful, carefree desert landscape.
Author Bio
Deane Alban is the creator of Southwest Gardener. She is a science writer with a bachelor’s degree in botany from the University of South Florida. Gardening is her lifelong passion. She’s been gardening in Tucson for 15 years.
