How to choose milkweed for your garden, landscape

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Habitat loss is one of the most important factors in the decline of monarch butterfly populations. There are fewer stands of milkweed than ever before due to increased land development for agricultural and other purposes and the increased effectiveness of herbicides used to control uncultivated plants.

Monarch butterflies depend on milkweed as host plants, which means they will only lay eggs on these plants, since milkweed is all the monarch caterpillars eat. This specialized diet offers some protection against predators. Milkweeds contain poisons known as cardiac glycosides, which monarchs have evolved to assimilate. These toxic compounds make them unpalatable to many predators.

There are 13 species of milkweed native to Ohio that monarch butterflies will use as host plants:

  • butterfly grass
  • Kissing-leaved Milkweed
  • common milkweed
  • green milkweed
  • Green Flowering Milkweed
  • honey-vine
  • milkweed
  • purple milkweed
  • spider milkweed
  • Sullivant’s Milkweed
  • marsh milkweed
  • white milkweed
  • Milkweed

Butterfly milkweed, common milkweed, purple milkweed, Sullivant’s milkweed and swamp milkweed are preferred larval hosts. Of these, butterfly weed, common milkweed, and swamp milkweed are most readily available in seed packets and as live plants at a local nursery. You can narrow down what will work in your yard or garden based on the growing conditions present.

butterfly grass

Height. Butterfly grass is the shortest variety of the three, reaching about 2 to 3 feet tall in a garden.

Terms. Butterfly grass grows best in a dry, sunny location with alkaline soil.

Flowers. It takes a few growing seasons before butterfly grass flowers when planted from seed. Once mature, it will attract a number of pollinators and butterflies with its bright orange flowers throughout the summer. The flowering period can be extended by cutting the butterfly weed flowers to prevent them from going to seed.

Planting. Milkweed seeds are best sown in the fall no deeper than ¼ inch. They can also be started indoors and transplanted in late spring, but the seeds should be stratified in the refrigerator for several weeks before planting to stimulate germination. If you buy live plants from a nursery, choose smaller ones as they will establish more easily.

marsh milkweed

Height. Swamp milkweed grows to about 3-4 feet tall. Each plant usually has a single stem with branches near the top.

Terms. This variety prefers to grow in moist to wet soil near ponds or bogs in full sun to partial shade. However, it can be grown in drier locations with supplemental watering. It grows naturally in abandoned fields and areas with disturbed ground. It doesn’t like being crowded with other plants, can become unsightly in the fall, and attracts aphids. It performs best when planted in a border rather than in a garden.

Flowers. Swamp milkweed takes on clusters of flat pink to purple flowers atop its stems in July and August. Its flowers give off a slight order of cinnamon.

Planting. Seeds are best sown in the fall at a depth of ¼ inch. They can also be planted in the spring after several weeks in the refrigerator. If you are buying swamp milkweed as a live plant, make sure it is in the ground before late spring and stick to the smaller ones for easier establishment.

common milkweed

Height. Common milkweed is the tallest of the three varieties, usually reaching about 3 feet tall and, occasionally, reaching heights of up to 5 feet. Like swamp milkweed, it grows as a stem with few branches at the top.

Terms. Common milkweed grows best in sunny, dry locations, but can survive in a variety of conditions. It is probably better suited to a wildflower garden than a well-tended garden, as it spreads by rhizomes and can form large clumps.

Flowers. Common milkweed flowers grow in ball-shaped clusters that range in color from pink to light purple. The flowers give off a sweet fragrance that can be detected from several feet away. This strain also gets large, comma-shaped pods that are thick and covered in thorns.

Planting. Sow seeds in the fall ¼ inch deep or in the spring after stratifying your seeds in the refrigerator. If you buy and plant live plants, transplant them outdoors before late spring. Smaller live plants will transplant more easily.

Tips

  • Milkweed plants grow easily when planted from seed, so starting them that way in the fall is your best bet.
  • Make sure the location you choose provides enough space for the varieties you have chosen to thrive and meet their growing needs. Milkweed plants have large taproots and do not transplant well.
  • Have patience to establish your milkweed stand. Most varieties grown from seed will not flower until their second year.
  • Milkweeds are important host plants and provide nectar for adult butterflies and other pollinators, however, you should also consider adding native wildflowers to the mix. Some favorite varieties include:
    • ash sunflower
    • black eyed susan
    • Dense Blazing Star
    • New England Aster
    • Ohio Goldenrod
    • Bullseye Sunflower
    • Prairie wharf
    • purple echinacea
    • Rattlesnake-Master
    • barren aster
    • smooth aster
    • Joe-Pye spotted
    • stiff goldenrod
    • Great Iron Grass
    • Narrow-Leaved Mountain Mint

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