Beneficial Insects, Flowers

Showy Milkweed: Growing Asclepias Speciosa Plants


Showy milkweed

Showy milkweed (Asclepias speciosa) is well known as a host plant to monarch butterflies. This is especially true with social media movements and many organizations offering free milkweed seeds to help encourage the establishment of this perennial flowering plant. There are over 100 species of milkweed plants that are native plants in North America, so chances are that you’ll be able to find a native milkweed species to add to your butterfly garden! Showy milkweed is native to the western half of the United States.

These fragrant flowers attract beneficial insects such as butterflies, hummingbirds, honey bees, and wild native bees. It also attracts milkweed beetles, named as such because they exclusively feed on milkweed plants. These beetles don’t bite or sting and won’t do much harm other than munching a few leaves. If the population of milkweed beetles becomes too large, they can easily be picked off of plants and squished. Milkweed beetles evolved to utilize milkweed’s toxic milky sap to their benefit. They eat milkweed, which in turn makes them toxic to anything that would attempt to eat them. Monarch caterpillars deploy this same chemical defense strategy which they carry into adulthood, making monarch butterflies toxic as well. 

As the name showy milkweed would suggest, the milkweed blossoms are ornate and add a stunning pop of color to your butterfly garden. Their star-shaped flowers in round clusters are reminiscent of fireworks and generally begin to bloom in mid-summer. By late summer, the blooms will all be spent, and the energy in the plant will be focused on producing seeds and seed pods. 

There is some caution to be used when choosing a site for your milkweed as it is toxic to people and pets alike. It should be planted in an area not easily accessible to small children or pets. That being said, despite its toxicity, milkweed is actually edible! It is only toxic in its raw form. Once properly cooked (blanched), they can safely be eaten. It is worth noting to use extreme caution when choosing to consume milkweed as it can easily be mistaken for other plants in the dogbane family which are unsafe to consume. Treat this as you would treat foraging for wild mushrooms. When in doubt, consult an expert, or don’t consume it at all. It’s also worth noting that, as with other foods, some people have a sensitivity to milkweed, so it’s best to try it in small amounts if it’s your first time eating it. 

Despite its toxicity, the benefits of adding these nectar plants to your gardens are worth it! They provide pollinators and beneficial insects with much-needed habitat; above all else, they support monarchs as their larval host! A quick Google search will help you determine whether or not you live in a monarch migration path and which milkweed is native to your area. If you’re lucky enough to live inside of the migratory paths, then you may also be lucky enough to spot monarch caterpillars on your plants and watch them transform into beautiful butterflies.

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Quick Care Guide

Showy milkweed flowers
Showy milkweed flowers live up to their name. Source: Thayne Tuason
Common NameShowy milkweed, Colorado milkweed
Scientific NameAsclepias speciosa
FamilyApocynaceae (commonly referred to as the “dogbane” family because of their toxicity to dogs
Height & SpreadGrows upright, reaching 4ft tall, spreads via underground rhizomes
LightFull sun
SoilWell-draining
WaterDrought tolerant once established
Pests & DiseasesAphids, leaf miners, root rot, leaf spot

All About Showy Milkweed

Showy milkweed (Asclepias speciosa) is often mistaken for common milkweed. They both have central flower parts comprised of spherical clusters of small pink flowers. However, showy milkweed flowers have a more pronounced star shape consisting of five hoods with prominent hooks. Common milkweed flowers are smaller and more rounded. Showy milkweed grows in an upright columnar habit with broad blue-green leaves. 

Showy milkweed is native to North America and can be grown in USDA zones 4-9. It is a perennial in its native habitat, and though it dies back to the ground each winter, it comes back to life in early spring. To start new plants, collect seeds at the end of the season and sow them directly into the ground in the late fall. These seeds require stratification and therefore need to be winter sown in order to guarantee germination in the spring. 

Showy Milkweed Care

Older showy milkweed foliage
As showy milkweed ages, the foliage starts to yellow. Source: Bear Paw Battlefield

Asclepias speciosa is relatively care-free once established – other gardeners with experience can attest! There are a few things to note to help you pick the right spot in your garden. Then you’ll be enjoying it and the butterflies it attracts for years to come! 

Sun and Temperature

Asclepias speciosa requires a full sun environment that receives 6-8 hours of direct sunlight per day. Showy milkweed is native to the western United States and parts of Canada, and for this reason, they grow best in USDA zones 4-9. Common milkweed is its eastern counterpart. There are some central states where showy milkweed and common milkweed, among other members of the Asclepias genus, habitats overlap. Showy milkweed seeds require cold treatment to germinate, which is another reason why these plants are native to areas that receive a cold winter. 

Asclepias speciosa seeds will not germinate at temperatures above 85 degrees. The plants prefer temperatures of 65-75 degrees during the spring and summer while they put out new growth. They will handle the heat and drought once established, and with the cooler weather in fall, you’ll notice the formation of milkweed pods. These pods will dry out, split at the seam, and then burst open with milkweed puffs! The pods are full of many flat oval seeds that are attached to silks (much like a dandelion seed) and will take to the wind and spread. You can collect the seed pods once dried, before they burst, in order to spread the seeds more purposefully or to save them for future use. 

Water and Humidity

Asclepias speciosa is particularly drought tolerant once established, so overwatering is generally the issue here rather than underwatering. Water 1 inch per week until established, and then water every other week. Overwatering, especially in combination with humid environments, can cause fungal issues for milkweed. Water at the base in the early morning before the heat of the day. In the fall, once the pods begin to form, you can cease watering altogether. Asclepias speciosa will dry up and die back to the ground in the winter. 

Soil

Milkweed pods broken open
Milkweed pods dry out and break open to spread seeds. Source: greenwithenvygirl

Another benefit of adding showy milkweeds to your garden is their ability to tolerate a wide range of soil conditions. They’re not fussy when it comes to soil ph. They will tolerate poor soils with average fertility and don’t require any added compost or organic matter. They will not, however, tolerate poor drainage. Be sure to plant them in a site with good drainage and away from areas near downspouts or low-lying areas where water may pool after it rains. 

Fertilizing Showy Milkweed

Showy milkweed can be found growing wild in roadside ditches and in clusters in wooded areas deep in the mountains of the upper Midwest US. This tells us that they can not only survive without fertilizing but flourish and multiply. That being said, if you’d like to increase the number and size of your blooms, you can do so with a dose of phosphate fertilizer as soon as the buds appear. Otherwise, your milkweed with be just fine without it! 

Pruning Showy Milkweed

Showy milkweed can easily take over an area because of the way they spread via underground rhizomes. To keep it manageable in a garden setting, it may be necessary to prune back showy milkweed as it begins to spread. Or you can use this to your advantage and place it in an area where you can allow it to spread in a cluster. Suppose you want to avoid the issue of spreading or managing its containment altogether. In that case, you may consider planting showy milkweed in a raised bed or large container like an old whiskey barrel. If a whiskey barrel isn’t available to you, we recommend a Root Pouch grow bag or an Air Pot. At the end of the season, after the seed pods (technically the plant’s fruit) have released their milkweed puffs, the stalks will be completely dried and can be cut with hand pruners back to the ground level. 

Showy Milkweed Propagation

The easiest way to establish milkweed in your garden is to direct sow seeds. In fact, in all species, milkweed propagation is most easily done by seed. Showy milkweed seeds require cold treatment via stratification. Stratification is the process that seeds naturally go through when they lay dormant in the soil during the cold winter. The warming weather in the spring then signals the seed to sprout and begin to grow. This special treatment for the seeds is necessary to guarantee germination. Showy milkweed seeds can sometimes be tricked into thinking they’ve gone through this dormant period by placing them in a refrigerator for a few weeks before planting them out. However, direct sowing the seeds in the fall is your best bet. 

Showy milkweed tends to have a long and deep taproot, making transplanting milkweed difficult and mostly unsuccessful. That being said, because they spread via rhizomes, it is sometimes possible to propagate milkweed plants via rhizome cuttings. If you notice a young shoot coming up near a mother plant, then dig it up, including the rhizome, and transplant it to a different area. It’s important to do this while the shoots are young and before the taproot becomes too deep to easily dig up. Do this on a cool and overcast day without any extreme heat in the near forecast. This will give your milkweeds time to establish. 

Troubleshooting

Yellowing Asclepias speciosa
As summer wanes, the milkweed yellows. Source: Bear Paw Battlefield

When planted in the appropriate zone, milkweed tends to flourish with very little intervention. There are, however, a few issues that can arise. Here we’ll discuss some tips and tricks to deal with any potential issues that may arise. 

Growing Problems

Chlorosis is the yellowing of the leaves that can have several causes, including poor drainage, damaged roots, compacted roots, or an iron deficiency. To troubleshoot the problem, check the soil around your Asclepias speciosa. If it is well-draining and not compacted around the roots, it may be more likely a nutrient deficiency. A foliar spray with an iron compound will temporarily improve the foliage. However, amending the soil will be needed for lasting results. 

Pests

Aphids, specifically oleander aphids, are the most common pest of Asclepias speciosa. In a well-balanced ecosystem, ladybugs, lacewings, parasitic wasps, or syrphid flies will show up shortly after the appearance of these aphids for a feast. These predatory insects can make quick work of aphid infestations. In situations where the good bugs may be delayed or the infestation is becoming severe, you can spray them off the plant with a blast of water. In extreme cases, neem oil can be used, but this should be a last resort since your milkweed may also host monarch caterpillars and monarchs who lay eggs on stems and leaves. 

The leaf miner is a small larvae that feeds between the two layers of leaf material. If you see a swirling pattern appearing on the foliage, this is an indication of leaf miners. The only way to control leaf miners is to remove infected plant material. In extreme infestations, alternative insecticides such as spinosad spray may be considered. However, it’s important to consider the potential effects on monarchs, monarch eggs, and caterpillars that may be using your milkweed as host plants. 

Diseases

Leaf spot on showy milkweed is usually red, brown, or black. The spots often start small and begin spreading to infect the entire leaf to the point that it drops from the plant. Severe infections can defoliate the plant completely and infect stems. The fungus spores that cause leaf spots are airborne and waterborne. Therefore, this disease is far less serious in dry climates with low rainfall. Growing milkweed in an area with low humidity year-round can help prevent this issue. Trim infected leaves to prevent the spread and dispose of infected plant material carefully. 

Root rot is caused by overwatering of Asclepias species. Excess water can suffocate plant roots. Showy milkweed needs well-draining soil. The symptoms of root rot will appear as a soft mushy stem, wilting, and of course, rotten roots. This type of rot is hard to recover from but can be remedied if there are still fresh white roots on the plant that have not yet turned to mush. Milkweed does not like to be transplanted. The best course of action to correct root rot is to back off watering and increase draining of the surrounding soil. 

Frequently Asked Questions

Showy milkweed
Showy milkweed is a host plant for monarch butterflies. Source: Matt Lavin

Q: Is showy milkweed toxic?

A: Yes and no. All milkweed species contain cardiac glycosides, making them toxic to humans and animals in their raw state. However, showy milkweed is the least toxic and can be eaten when properly prepared. The buds, flowers, leaves, and shoots are all edible when blanched. It is important to note to take extreme caution and be sure to correctly identify this plant before cooking and consuming it (as it can easily be confused with other lookalikes and species in the dogbane family). Treat it with the same caution that you would when identifying and consuming wild mushrooms. When in doubt, either consult an expert or just don’t eat it.  

Q: Is showy milkweed invasive?

A: Despite its name, milkweed is not a weed. It is a native wildflower and is not considered a noxious weed in any state in the US. 

Q: Where should I plant showy milkweed?

A: Pick an area that receives full sun. Remember they can grow up to 4ft tall so be sure to plant them on the north side of your garden so that they don’t shade out smaller plants. 

Q: Is showy milkweed annual or perennial?

A: Showy milkweed is a perennial. 

Q: Is showy milkweed aggressive?

A: No, although it can spread aggressively via underground rhizomes if left unchecked, it can be cut back and controlled relatively easily. 

Q: Does showy milkweed attract butterflies?

A: Showy milkweed is most notably the host plant of the monarch butterfly. They are also known to attract the red-belted clearwing moth, the dogbane tiger moth, and the queen butterfly. 

Q: Is showy milkweed toxic to dogs?

A: Yes, all parts of the plant (seeds, stems, leaves, and flowers) are toxic to dogs and cats. 

Q: Where should you not plant milkweed?

A: Because of its toxicity, it’s best to not plant milkweed in reach of pets or small children. 

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