Here's what you need to know about milkweed to attract monarch butterflies | Sally Scalera

Milkweed is the host plant for butterfly enthusiasts who want to attract monarch butterflies.

When the monarch discovers the milkweed, she lays her eggs on it. Once the eggs hatch, the small caterpillars eat and molt, repeating that process again and again until they form their chrysalis.

They complete their entire life cycle either on or near the milkweed plant.

Monarch butterflies are unique because they migrate south for the winter, and it is important that they migrate every winter.

Native milkweed species are the best plants to grow because they die back to the ground in the fall and don’t begin growing again until the spring.  This is great for the monarch butterflies because when the plants disappear, the monarchs fly south.

Tropical milkweed (Asclepias curassavica), on the other hand, is native to Mexico and produces clusters of red and yellow tubular flowers throughout the year. In garden centers, it is often labeled as butterfly weed.

If you are growing a solid yellow milkweed, your plant could be a yellow flowering form of our native butterfly weed, Asclepias tuberosa. There is also Asclepias curassavica Silky Gold tropical milkweed that produces yellow flowers.  The easiest way to tell the two species apart is to snap a leaf off to see if it has a milky sap. The plant is a non-native tropical milkweed if milky sap begins to flow. 

When growing tropical milkweed, it’s important that the plant is cut down to protect the monarch butterflies (along with the queen and other butterflies in the Danaus genus) from disease. Monarch butterflies have a protozoan parasite, Ophryocystis elektroscirrha or OE, that infected butterflies carry with them.

When an OE-infected monarch visits a plant, some OE protozoans are deposited on the plant. Caterpillars ingest protozoa, along with the leaf, when eating. The level of OE can build up on a plant over time.

Caterpillars that consume large amounts of OE, as adult butterflies, may not survive metamorphosis. If they do, they may have reduced body mass, mating success, flight ability, and life span because many don’t survive migration.

The OE protozoa can be found on our native milkweeds also, but our native species die to the ground every fall, and the parasites die with it. Therefore, every summer, the new monarchs feed on parasite-free foliage.

To provide the caterpillars maximum protection, cut your tropical milkweed down twice, once in June and again at Thanksgiving. The first cutting will reduce the buildup of OE on the plant, and the final cutting at Thanksgiving will keep the plant from blooming through the winter so the Monarchs migrate south.

Another precaution to take when growing tropical milkweed (to protect our natural areas) is to prune off the faded flowers so seed pods aren’t produced. This will also benefit the plants because they won’t be expending energy to produce seeds but can instead produce new growth and/or more blooms.

If you discover that you have the non-native Silky Gold butterfly weed (look for smooth stems and milky sap), follow these same pruning suggestions.

Research done by the University of Florida has also discovered that planting wildflowers and milkweeds together increases the number of monarch butterflies that are produced in the area. In the areas where other flowering plants were planted with the milkweed, they found that the monarchs laid 22% more eggs.

Diverse plantings provide a greater benefit for a variety of organisms. Though the caterpillars need milkweed plants as their food source, the adult butterflies need more than just milkweed flowers as a nectar source, so diverse wildflower patches are more appealing to the adult monarch butterflies.

Florida has 24 species of native milkweeds, 11 of which are found in or around Brevard County. Florida native milkweeds can be found in various soil conditions, ranging from very wet to very dry.  Here are some native species that prefer to grow in dry sandy areas such as pastures, sandhills or along fence rows.

• Butterfly weed, Asclepias tuberosa, has the largest native range and can be found throughout the Eastern United States and much of the Southwest, though not in California. This native species produces bright orange or yellow flowers that bloom from spring through the fall. It’s found in sunny, dry, upland sites with sandy soil. Not only do the flowers attract bees and other pollinators, they also attract hummingbirds. The plants will grow 1 to 3 feet tall and spread 1 to 2 feet.

• Pinewoods milkweed, Asclepias humistrata, has been vouchered in Volusia, Orange, and Osceola counties, so it is probably growing here in Brevard also. Find a sunny spot for this milkweed to grow 1 to 3 feet tall. The plants bloom in spring and continue through summer, producing pink, lavender, and white flowers.

If your yard has moist or wet areas, consider these native milkweed species.

Whorled milkweed, Asclepias verticillata, is considered a small annual plant that grows best in sandy, moist areas that never get extremely dry. The showy flowers mix well with other wildflowers and will attract various pollinators in addition to the butterflies.  A word of warning: this species is the most toxic of the milkweeds and is considered a weed where livestock graze.

Swamp milkweed, Asclepias incarnata, produces showy, pink flowers in sunny locations. The plants grow in large clumps that reach 3to 6 feet tall.  This species is considered one of the most striking of the native species, and they will also attract our native bees.

Aquatic milkweed, Asclepias perennis, is another species that has been vouchered in Volusia, Seminole, Orange, and Osceola, and to the west and south to the Gulf of Mexico.  It produces white flowers that grow 2 to 3 feet tall in partial to full shade locations.

There are a number of other native milkweed species that will be more difficult to find for sale, such as the Largeflower milkweed, Asclepias connivens, Curtiss’ milkweed, Asclepias curtissii, Florida milkweed, Asclepias feayi, Fewflower milkweed, Asclepias lanceolata, and Velvetleaf milkweed, Asclepias tomentosa.

If you are already growing tropical milkweed, make a note on your calendar to cut the plants back at Thanksgiving and again in June. Be sure to cut them down to the ground at Thanksgiving because it is important that the monarch butterflies fly south for the winter.

If you want to start gardening for monarch butterflies, consider planting some native milkweed species mixed with wildflowers. What a great way to beautify your yard and help the monarch butterflies.

Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Sciences. Email her at sasc@ufl.edu.

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This article originally appeared on Florida Today: How to bring monarch butterflies to your yard with milkweed