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growing milkweed from seed

The Monarch Butterfly Crisis: Growing Milkweed for Maximum Benefit

You've already heard that agricultural herbicides and pesticides are decimating important pollinator food sources. This is true; the iconic monarch butterfly population, for example, all but crashed. In the closing months of 2018, studies released by top butterfly conservationists found that monarch counts have drastically declined in the past two decades, with the most recent years stunning those who are paying attention.

Changing weather patterns, environmental chemicals, and loss of food sources are the primary factors for the literal decimation of monarch numbers. The monarch butterfly prefers milkweed nectar above and beyond any other and only lays its eggs on milkweed plants. The emerging caterpillars aren't just picky; they're genetically wired to only eat milkweed leaves.

No milkweed, no monarch butterflies.

Milkweed's white, viscous sap is mildly toxic to other species, and monarch caterpillars develop a tolerance...but the toxicity affects predators that eat them. The caterpillars' distinctive yellow, black, and white stripes, which resemble trendy print patterns you'd expect to find in an IKEA catalog, serve as a visual warning to their enemies: Bug off! Caterpillars may benefit from using scare tactics, but the flurry of media coverage? That's not fake news; this is serious.

We'll talk more about butterflies later, and how home-grown milkweed can help the plight of these endangered insects. First, we'd like to point out that milkweed plants aren't just utilitarian; they deserve credit as garden-worthy ornamentals. Did you ever see that 1998 Friends episode in which the characters debated whether or not altruism was actually self-serving? It is, actually. We feel good when we're helping others, but admit it: even the best of us aren't going to make room in our gardens for junky-looking plants.

Milkweed as an ornamental: Conservation ain't never been so purty

The name "milkweed" doesn't conjure up the image of sublime beauty. If you're not familiar with the Asclepias genus, we don't blame you if you associate anything ending in "weed" with pure evil, or with driving 20 miles per hour in a 55 zone while listening to Iron Butterfly. (As if there's a difference.) But we assure you that, even if the monarch population was thriving, you'd admire the plants and their colorful flowers for their ornamental value alone.

Some milkweed species are considered tropical, while others withstand colder, more northerly climates. Otherwise, their cultural requirements are roughly similar, so we're going to use common milkweed (Asclepias syriaca) as our standard of reference.

Milkweed is a quick-to-mature, easy-to-grow, showy plant. Upright, sturdy, somewhat hairy stalks bear umbrella-shaped clusters of tiny, star-shaped flowers. Bloom color may vary from pinks to mauves to fiery orange, but all members of the milkweed family (Asclepiadaceae) have five small, green sepals that cling to the swelling buds; when the plants open, the five petals droop down and curl upwards at the tips.

Milkweed flowers have distinctive vertical, waxy coronas, which are essentially a second set of petals surrounding the flower's reproductive organs. Save Our Monarchs describes each individual corona petal as "beak-shaped," and they nailed it.

Milkweed ovaries develop into ribbed, elongated, bumpy or spiny pods, which in turn release "flossed" seeds that scatter in the wind much like dandelion fluff. Milkweed reproduces rapidly in this manner, or through spreading rhizomes.

Bright to dark-green oblong or ovate leaves either grow opposite one another from stem nodes or in a whorl pattern. Milkweed earned its name from the white fluid sap which bleeds from its broken stems and crushed leaves. When you're handling milkweed plants, you might want to wear gloves as some people might develop a mild skin rash after contact with the sap. If you have highly sensitive skin, butterfly milkweed (Asclepias tuberosa) is a sap-free species.

Always refer to your seed packet for species-specific recommendations, or if you have any questions, contact us for help.

  • USDA Hardiness Zones: Most milkweed perennials and all annuals do well in zones 3 to 9.
  • Sunlight Preferences: Full sun.
  • Moisture Requirements: Drought tolerant, but consistently moist (not wet) conditions produce the best blooms.
  • Soil Preferences: Thrives in poor soils, as long as it's well-drained. It prefers slightly acidic soils in the 4.8 to 6 pH range.
  • Plant Width: 12" to 18" spread.
  • Bloom Period: June through August.
  • Maintenance: Cut down perennial and annual milkweed plants after they wilt from the first hard frost...or sooner (See below).

The obvious milkweed pest is the monarch caterpillar, but other bugs can come in and hog the buffet. Some of the following culprits have species that are actually specialized to feed on milkweed. Watch out for aphids, Japanese beetles, red-and-black milkweed beetles, leaf miners, snails, and slugs.

You'll be happy to know that deer, at least, don't like milkweed.

Milkweed makes an excellent fresh-cut or dried flower. Be sure to put the stems in water immediately after cutting. Gather them with other umbrella-blooming plants such as bishop's flower or angelica for a frothy, delicate arrangement.

Preventing "failure to launch" syndrome

Heavy agricultural herbicide use is the primary cause of monarch decline, but sometimes, the road to hell is paved with good intentions. When word got out that monarchs were in decline, well-meaning gardeners began strafing their yards and open spaces with milkweed seeds...without realizing the potential drawbacks.

Closing time...You don't have to go home but you can't stay here. — Semisonic. 1998

Depending upon where you live, you should take steps at the end of the season to prevent freeloading butterflies from moving along on their natural migration route. Some tropical varieties such as Asclepias curassavica can live year-round in warmer US regions, preventing monarchs from migrating to Mexico—an essential step in their lifecycle. When A. curassavica, commonly known as bloodflower or Mexican milkweed, is allowed a long life, it becomes host to the parasitic protozoa Ophryocystis elektroscirrha. Monarch caterpillars consume the parasite, which then deforms or weakens them when they're in the metamorphic phase. Emerging infected monarchs rarely survive to reach breeding age.

We recommend you treat all milkweed species as annuals and remove from your garden at certain times of the year—depending on your location—to encourage monarchs to move on. This also breaks the parasite life cycle in tropical milkweed gardens. But by no means should you be hesitant to grow these important plants, not just for their role in the ecosystem, but for their value as an ornamental.

Milkweed's history and anecdotal usage

Asclepias is a derivative of Asklepios, the Greek god of medicine. The genus name was originally assigned to milkweed's Old World look-alike, dogbane, by the first-century Greek physician. Asclepias was later used to classify true milkweed, which is a North American native. When discussing milkweed's anecdotal therapeutic value, it's important to know how to tell it apart from dogbane...both in writing and in the field.

European explorers first carted milkweed back to the Old World in the 16th century and The Farmer's Almanac (the gardener's version of Reader's Digest) reports that Native Americans valued milkweed as a treatment for warts, dysentery, asthma, and typhus. They also used fibers from milkweed stalks to make cordage or cloth.

There are more than 200 milkweed species in North America with overlapping or specific native habitats. As a family, they've adapted to nearly every biome on the continent. Monarch Watch has a fantastic map and list of milkweed profiles, and we encourage you to learn more about choosing the best species for your climate as it relates to the monarch butterfly's migration patterns.

Growing milkweed from seed

For optimal germination, we recommend treating milkweed seeds with 1 to 3 months' cold stratification between 40°F and 50°F prior to planting. No room in your refrigerator? Place the seeds outdoors in the winter to take full advantage of the natural frost cycle. Starting your milkweed seeds indoors will help provide early blooms and the most nutritious leaves.

  • When to Plant Outdoors: Plant cold-stratified seeds as soon as the last spring frost has passed.
  • When to Plant Indoors: 6 to 8 weeks prior to your desired transplanting date or last spring frost.
  • Seed Depth: No more than 1/8" deep.
  • Seed Spacing: Plant or thin 18" to 24" apart.
  • Days to Germination: 7 to 14 days at 70°F.

Once your milkweed starts have grown either four leaves or four inches, they're ready to be kicked out to their garden location. We recommend planting a few different varieties around the garden to ensure the butterflies can find pest-free, healthy plants. Some gardeners like to plant them where they can serve as "pest magnets."

Our commitment to conservation

We love all plants that support pollinators and feel it's important to offset depleted plant species so that important insects can continue to thrive. Right now, it's more important than ever to try growing milkweed from seed and to be mindful of how fragile our ecosystem really is. The alarming decline of the monarch butterfly is only one example of the symbiosis between plants and the animal kingdom. What we might dismiss as a "weed," beautiful or not, might be essential to species that play a critical role in our natural environment.

Reach out to us for recommendations on pollinator-safe herbicides and pesticides, and to learn more about other plant species that support endangered insects, like lupine's relationship with gorgeous Karner blue butterflies. And if you're aware of other native insects that require a little extra love and care, let us know and we'll happily spread the word!
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