The Ultimate Guide to Growing Milkweed

You’ve probably seen Monarch Butterflies in the news a lot over the last few years and unfortunately, not for good reasons. There’s been a sharp decline in the population of Monarch Butterflies and it is now listed as an endangered species (source). The Monarch Butterfly is a migrating species of butterfly that spends its winters in Mexico and then travels thousands of miles North to its breeding grounds in North America and even into Canada. The main culprit for the population decline is habitat destruction, specifically that of the genus Asclepias, otherwise, known as milkweed. Fortunately, for the Monarch Butterflies and those who love watching the majestic beauties, there is a solution: growing milkweed in our home gardens.

Why Grow Milkweed?

Milkweed, and so many other North American native plants, have the unfortunate name “weed” included in it. Unfortunately for milkweed, many homeowners have treated it as so. They’ve categorized it as a weed and treated it that way, nearly eliminating it from the home landscape.

So why grow milkweed? Not only is milkweed extremely important in the ecology of Monarch Butterflies, it also acts as a food source for hundreds of other insects. Planting milkweed species native to your area directly supports both monarch butterflies and other pollinators and organisms that feed and live on the plant.

In general, milkweed is actually quite toxic to most insects. However, through natural selection, the monarch butterflies and other specialized insects have formed an immunity to the otherwise toxic plant. For monarch butterflies, milkweed acts as the only host plant for their caterpillars. As a result, they feel the brunt of destruction as more and more land turns into sterile lawns and invasive species outcompete milkweed. So, why grow milkweed? Well, it is the number one way to support Monarch butterflies and further prevent the population decline.

Choosing the Right Milkweed Species

There are 100’s of species of Asclepias in North America and depending on what type of landscape you are after, there is a perfect choice for you. Most traditional landscapers find milkweed to be a weed and remove it from their gardens. But you are not a traditional gardener if you are here reading this blog. Below are the most common types of milkweed here in the Northeast. Depending on the species, it can grow several inches off the ground to even a couple of feet tall. Blossoms in summer range from pink to orange and are a pollinator magnet, as well as the host plant for Monarch Caterpillars.

The Xerces Society has several FREE guides to help you select native milkweed based on your region. Take a look and be sure to plant straight, native species in your location. Oftentimes, big box stores will sell “milkweed” species labeled Asclepias spp. These often aren’t native species. The best way to ensure a straight native species to your region is to go to a local native plant store. If there isn’t one nearby you could always inquire about shipping seeds.

Planting Milkweed Seeds

Growing milkweed from seed can actually be quite simple. Seeds can be harvested from the plant in late fall once the pods open up. Milkweed requires a period of cold stratification. If you’re unfamiliar with cold strationfaction, you can learn about the process here. Milkweed requires about 30 days of cold stratification. You’d see this labeled as C30 on a purchased packet of seeds. Cold stratification can be accomplished in a few different ways.

Natural Cold-Stratification

The simplest way to cold-stratify seeds is to let nature do it. Plant the milkweed seeds outside in late fall or early winter and let nature do its thing. If successful, seeds will germinate in the spring when temperatures are warm enough. The only downfall is seeds are more vulnerable to birds or small mammals but is presumably less work than artificial stratification. You’d also need to remember where you planted it and not mistake it for an actual weed in the spring. You can read about cold-stratification in milk jugs which offers protection from hungry critters.

Artificial Cold-Stratification

Artificial cold stratification involves replicating the cold winter, typically inside a fridge. Mix sand with a little bit of water. Enough to moisten the soil but not enough to wring it out. Mix in the seeds, label the bag and put it in the back of your fridge. Forget about it for 30 days. The nice thing about artificial cold stratification is it can be done year-round, especially if you forget to do it the natural way, ie. starting in April like me this year. After the cold stratification is completed, remove the seeds and either plant directly into the ground or into a pot. I’ve had successful germination rates both natural and artificial.

Dealing with Pests

As a gardener, you’re bound to run into a pest or two. Milkweed, despite its toxicity, is no exception. The most common problem, I’ve encountered when growing milkweed is oleander aphids. Last year, my swamp milkweed was completely overtaken by oleander aphids. They destroyed the blooms and I saw zero monarch caterpillars the whole summer. I waited and waited for ladybug larvae to do their job but that never happened despite having many ladybugs in my yard. Turns out, oleander aphids do a good job escaping the predation of ladybugs.

By the end of summer, the swamp milkweed was destroyed and there were very few seeds. Luckily, the milkweed seems to be returning this year. This year though, I will not wait around. I plan to squish the aphid population if it becomes too dense again. Whatever you do, DO NOT SPRAY insecticide on the plant, as this will harm the monarch caterpillars we’ve set off to help!

I’ve had small milkweed bugs on my plants, but never out of balance that it has been a problem. They are native and have also coevolved with the milkweed plant. I don’t consider them a pest as long as they don’t become a problem. Time will tell though.

What to do next?

If you want to support Monarch Butterflies, you must provide them with the essential necessities. The dependent relationship of monarchs on milkweed means if milkweed disappears so do the beloved monarch butterflies. We can prevent their disappearance. We can grow milkweed. It is a simple and effective solution. Not only will including milkweed in your home landscape support monarchs but other pollinators and insects as well. Happy Milkweed planting!