Tips for Cultivating and Maintaining Common Milkweed

David Beaulieu is a seasoned landscaping professional and a skilled plant photographer, boasting two decades of expertise in his field.

Common milkweed (Asclepias syriaca) is a native perennial herb that attracts butterflies, particularly the monarch butterfly. This plant is the sole host for monarchs to lay their eggs. The caterpillars, or larvae, of the monarch feed solely on the plant’s thick, elongated leaves. It typically grows to a height of two to four feet, exhibiting a slender, upright form. From late spring to mid-summer, it produces fragrant clusters of pinkish-purple flowers.

Sow seedlings in early spring once the risk of frost has diminished, and plant seeds directly in the soil during late autumn.

The foliage of milkweed and its milky sap are poisonous to humans, pets, and livestock, making it a source of concern for farmers who find it growing in their fields.

Light

Common milkweed thrives in bright, direct sunlight, ideally in a location that receives six to eight hours of sunlight daily.

Soil

This plant favors well-drained soil that is dry to moderately moist. It is capable of withstanding arid environments, poor soil quality, and rocky terrains. It flourishes in soil with a pH level between 4.8 and 7.2.

Water

Common milkweed typically requires no additional watering unless faced with extremely dry conditions. When watering, provide a thorough soak of one to two inches, and allow the top inch of soil to dry out before the next watering. Excessive watering can lead to root rot in common milkweed.

Climate and Moisture Levels

Common milkweed can withstand various temperature and humidity levels. However, as it originates from the eastern regions of the United States, it struggles in conditions of intense and prolonged heat or humidity. During the winter months, the plant enters a dormant state.

Fertilizer

Fertilizing common milkweed is unnecessary, as these plants can thrive in nutrient-poor soils.

Varieties of Associated Milkweed Species

Milkweed plants are the primary food source for the endangered monarch butterfly, making the addition of a few patches in your garden a vital step in supporting the survival of this species. The United States is home to over 100 native varieties of milkweed. Alongside the common milkweed, several other popular species within the Asclepias genus are available, each varying in height and flower color:

• Butterfly weed (Asclepias tuberosa) reaches heights of 1 to 2 feet and features bright orange flowers. It is indigenous to the northeastern region of the United States.
• Swamp milkweed (Asclepias incarnata) reaches a height of 4 to 5 feet and features flowers in shades of mauve, pink, or white. This plant is indigenous to the northeastern and southeastern regions of the United States.
• Showy milkweed (Asclepias speciosa) reaches heights of 1 to 3 feet and features vibrant rose-purple and pink flowers. This species is indigenous to the western regions of the United States.
• Purple milkweed (Asclepias purpurascens) reaches heights of 3 to 4 feet and features striking red-purple flowers, native to the eastern regions of North America.
• Whorled milkweed (Asclepias verticillata) typically grows between 1 and 2 feet in height and features white flowers. This plant is indigenous to the eastern regions of North America.
• Sandhill milkweed (Asclepias humistrata) typically grows between 1 and 3 feet in height and features flowers in shades of pink, lavender, or white. This plant is indigenous to the southeastern region of the United States.

Cultivating Common Milkweed Species

Propagating common milkweed through cuttings is often simpler than dividing rhizomes, as milkweed typically develops deep taproots that can be difficult to excavate. By using cuttings, you can quickly produce new plants, making it an excellent option for those looking to establish a butterfly garden swiftly. Here’s a guide on how to propagate milkweed using cuttings:

1. In the middle of summer, when the stems of common milkweed are still green, you can propagate the plant by taking cuttings. Use a sharp, sterilized cutting tool to snip stems that are approximately four inches in length. Select green stems that have three to five leaf nodes.
2. Trim the lower leaves from each stem, leaving the top two pairs untouched. Apply rooting hormone to the base of the stems.
3. Position the cuttings upright in a planting medium composed of 80% perlite and 20% peat moss.
4. Position the pots in a cool, shaded area, avoiding direct sunlight as the stem develops roots. Ensure the soil remains consistently and evenly moist.
5. Once the roots have developed, transfer the cuttings into the soil after a period of six to ten weeks.

A Guide to Cultivating Common Milkweed from Seeds

If you have a milkweed plant growing in your garden, you won’t need to take any action to propagate it, since the seeds will naturally disperse when the pods open in the autumn. For a more intentional planting, you can spread milkweed seeds in late fall on a site free of weeds, ensuring they are covered with no more than a quarter of an inch of soil.

An alternative approach is to germinate common milkweed seeds indoors. Keep in mind that the cold stratification process, which enhances germination, requires 30 days, so it’s best to begin the seeds in March. Here’s the procedure:

1. Enclose the seeds in a moist paper towel and put them inside a zip-lock plastic bag in the fridge. Allow them to sit undisturbed for approximately 30 days.
2. Fill the peat pots three-quarters full with potting soil designed for starting seeds. Lightly wet the soil until it reaches a slightly damp consistency.
3. Insert one or two seeds into each container. Then, layer the seeds with a quarter-inch of soil.
4. Moisten the seed from the base. Place the peat pots on a level tray and pour in half an inch of water. The pots will take in the moisture.
5. Position the containers on a bright windowsill, beneath grow lights, or inside a greenhouse. Ensure the seeds remain consistently moist. Anticipate the emergence of sprouts in about two weeks.
6. In the spring, plant the peat pots directly into the soil. The pots will decompose gradually, allowing the milkweed roots to remain undisturbed.

Propagation of Native Milkweed

Milkweed blossoms generate bumpy seed pods measuring between two to four inches in length, which burst open when mature, releasing numerous tiny seeds into the air. These seeds can germinate in far-off areas of your garden (and even further), aided by their silky filaments that enable them to drift with the gentlest of winds, similar to dandelion seeds. This phenomenon takes place just before the arrival of colder temperatures, allowing the seeds to undergo natural cold stratification.

Frequent Insects and Plant Illnesses

Milkweed is susceptible to various pests and diseases, such as:

• Milkweed beetles and milkweed bugs, which generally cause minimal damage.
• Aphids
• Whiteflies
• Scale insects
• Spider mites are tiny arachnids that can cause significant damage to plants.
• Thrips
• Leaf miners are insects that create tunnels or mines within the leaves of plants as they feed on the tissue.
• Oleander aphids, known scientifically as Aphid nerii, are often referred to as milkweed aphids due to their appearance, resembling small orange eggs. These pests feed on the sap of the stems and leaves, leading to the wilting of flowers and pods, and in severe cases, they can be fatal to the plants. If you notice flies buzzing around the milkweed, they are likely drawn to the honeydew excreted by the aphids during their feeding.
• Snails and slugs have a fondness for young, delicate milkweed plants. Using snail bait is effective and safe for monarchs, and as the plants mature, the issue with snails tends to decrease.
• Fungal issues like leaf spot, verticillium wilt, and root rot can be problematic. Remove any infected leaves and branches impacted by leaf spot, but be aware that the other two fungal conditions might be challenging to manage.

Controlling Pests on Milkweed

Avoid applying pesticides to milkweed or any plants in a butterfly or pollinator garden, as these chemicals can harm butterflies and their larvae just as they eliminate harmful insects. Instead, consider using a hose, a spray bottle, or your fingernails to remove any pests.

Will common milkweed dominate my garden?

Exercise caution when selecting a location for milkweed cultivation. Common milkweed tends to spread vigorously through both seeds and rhizomes, often suffocating surrounding plants. It can dominate a mixed border garden unless your intention is to establish a butterfly garden. To manage its growth, consider planting it in a restricted area or in a part of your yard where its spread is acceptable. Nevertheless, common milkweed, along with other native milkweed varieties, is a valuable wildflower and is not classified as a harmful weed or invasive species.

What makes milkweed harmful to monarch butterflies?

Common milkweed is beneficial for monarch butterfliesin fact, it plays a positive role in their lifecycle. In contrast, tropical milkweed (Asclepias curassavica) poses a threat to monarchs. It lures these butterflies to feed on it throughout the winter, which disrupts their migration to warmer southern regions, ultimately leading to a decrease in their populations.

How about considering the idea of planting milkweed along the coastline?

If you reside in a coastal region or close to a place where monarch butterflies spend the winter, it’s advisable to cultivate nectar-rich plants like blazing star and bidens to aid the monarchs during their migration to and from their winter habitat. Adult monarchs primarily require milkweed for reproduction, and the presence of milkweed can misleadingly indicate to them that they are in a suitable breeding environment, thereby interfering with their natural migration patterns.