Planting milkweed in your garden is an easy and effective way to support endangered monarch butterflies. Milkweed species are the sole host plants for monarch butterflies which means they’re the only plants used by monarch butterflies for egg laying. The flowers of milkweed are also nectar-rich and feed monarchs as well as many other species of butterflies and bees.
Types of milkweed:
There are many species of milkweed you can plant, but the three types below are easy to source and easy to grow. Plus, they make beautiful, long-lasting garden plants.
Common Milkweed (Asclepias syriaca)
Hardy in zones 3 to 9, common milkweed is the best known milkweed and native to many parts of North American. The plants grow three to five feet tall and are topped with large, rounded flower clusters. The plants are aggressive spreaders, however, and can be invasive in a mixed garden. It’s best to plant common milkweed in a dedicated bed or a site where you don’t mind it wandering. If you can find a good space, don’t be discouraged from planting common milkweed as the monarch butterflies love it!
Swamp Milkweed (Asclepias incarnata)
Swamp milkweed is native to many regions of North American and hardy in zones 3 to 6. As the name suggests, it grows well in areas with wet soil, but also thrives in average garden soil. It’s a great choice for perennial beds and borders. Swamp milkweed won’t spread all around your garden like common milkweed but instead forms pretty clumps of foliage and flowers. Expect the plants to grow two to four feet tall with showy clusters of deep pink flowers in mid to late summer.
Butterfly Weed (Asclepias tuberosa)
Butterfly weed is not a weed at all, but an easy-to-grow, long-blooming perennial milkweed that attracts all sorts of bees and butterflies including monarchs. It’s also drought and deer-resistant and flowers from mid to late summer. Butterfly weed is hardy in zones 3 to 9. Unlike most other types of milkweed which have pink, purple or white flowers, butterfly weed has fiery orange flowers. It’s also compact and grows just two feet tall in tidy clumps. It won’t spread aggressively around your garden.
Milkweed planting tips:
Milkweed grows best in garden beds with full sun to partial shade. I have had excellent luck direct sowing swamp milkweed and butterfly weed seeds in autumn with the plants emerging the following spring. You can also start the seeds indoors under grow lights or buy transplants from a local garden centre. Space the plants 45 cm (18”) apart, and for best results, plant at least five to six plants to create a good-sized clump for the monarchs. If you only have one or two plants and they’re too small to sustain monarch caterpillars, the butterflies won’t lay eggs in your garden.
Encourage caterpillars:
Remember the whole point of growing milkweed for monarchs is to encourage the adult butterflies to lay their eggs on the plants. Once the eggs hatch and the caterpillars emerge you’ll start to notice damage to the plants. That’s ok! The caterpillars will feed and then form chrysalises, eventually emerging as adult butterflies. Milkweed is a hardy perennial and heavy feeding from the caterpillars won’t harm the plants.
