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OSU Extension

College of Food, Agricultural, and Environmental Sciences

September 29, 2015 - 4:02pm --

You have no doubt seen or heard about the declining monarch butterfly population. Home gardeners are encouraged to plant milkweed to provide the host plant for the monarch caterpillars. There are 13 varieties of milkweed native to Ohio, but three of these are the most commonly available in seed packets. These three species are very different in their appearance and their growth characteristics. Knowing the difference will allow you to select the species that will fit best into your home garden beds. 

Asclepias tuberose, butterfly weed, can grow to three feet tall but is usually about 2 feet tall in a garden. It appreciates a dry sunny location and does well in our alkaline soil. The flower clusters are bright orange to yellow and bloom through most of the summer especially if they are cut back to keep them from going to seed. Butterfly weed fosters patience. It often takes two or more years before it blooms and it sprouts very late in the spring, mine often don’t appear until late May or early June, so it is easy to assume they have died and plant something else in their space (ask me how I know). The bright orange flowers and relatively short stature make this an ideal plant for the middle of a sunny garden bed as long as the soil is not wet. If you buy live plants from a nursery, try to get small ones as larger plants are more difficult to transplant. 

Asclepias incarnate, swamp milkweed, is a much taller plant growing to 3-4 feet in height usually with a single stem with some branching near the top. The pink to purple somewhat flat flower clusters appear at the top of the stems in July and August and have a faint cinnamon odor. This plant prefers to grow in damp or wet areas near ponds or bogs in full sun or partial shade but will survive in drier areas if it gets sufficient water. It is often one of the first plants to grow in an abandoned field or other disturbed area but does not do well when crowded by other plants. The leaves are long and thin, turning slightly purple if the plant gets sufficient sun and the pods are held upright on the plant. This is a good plant for wet, even mucky, clay soil if there is sufficient sun. Swamp milkweed can become leggy and unsightly in the fall and it is also a magnet for aphids.  For this reason, along with its height, it is best at the back of a border.  

Asclepias syriaca, common milkweed, is the species you most often see along country roads and in our parks. It grows as a stalk up to 5 feet high but is usually about 3 feet in height. Unlike swamp milkweed, common milkweed has large broad leaves with a prominent central vein. The flower clusters are ball shaped and light pink to purple.  The pods of common milkweed are comma shaped, thick and covered with spines. Common milkweed prefers sunny, dry locations but grows in a variety of conditions. Be aware this plant spreads by rhizomes and can form large clumps. While it is one of the native hosts of monarch butterflies and has interesting seed pods for dried arrangements, it may not be the best species to plant in a well behaved garden. 

All three species grows easily from seed; possibly one reason why their name includes the word ‘weed’. Plant seeds directly into the ground in the fall covering them with ½ to ¼ of soil. Or give the seeds a few weeks at refrigerator temperature and plant outdoors in the spring. You can also start seeds indoors and plant them outside in late spring. It may take several weeks for seeds to germinate so have patience. Plants grown from seed will usually flower their second year. 

All three species have a large tap root and do not like to be transplanted so plan ahead and plant them where you will want them for years to come. Milkweed plants all contain a cardiac glycoside and are poisonous so deer usually do not bother them. Aphids will appear on almost all milkweed plants. They may be unsightly, but do not seem to harm the plants. If necessary wash them off with water or put on a pair of gloves and gently squish them. Please do not use pesticides on your milkweed as you will kill the insects you are trying to attract.  Monarch caterpillars are voracious and may eat most of the leaves off your plants leaving them unsightly, but given time they will regrow. 

Here are some interesting facts about milkweed. The floss from the seeds has been used to stuff pillows and even life vests. The fibers from the stems have been suggested as substitute for hemp and were used by native Americans to make netting and rope. Many parts of the plants were used for medicinal use by native Americans and if carefully prepared, even as food. Remember the raw plants are poisonous, please do not try this yourself. If you would like information on the other ten native Ohio species, please visit

Finally, while monarch butterflies depend on milkweed to develop, they also need abundant sources of nectar to survive as adults. This is particularly important in the fall as they are migrating. As our neighborhoods are mostly flowerless lawns and evergreen shrubs, it is very important to provide flowering plants to support the butterflies. Plant native wildflowers if possible, but even easily grown zinnias will help provide nourishment as the butterflies fly south.

For more information on home, lawn, indoor, or outdoor garden care and tips, as well as other garden topics, visit and click on the Yard and Garden link, or call the OSU Extension, Butler County, at (513) 887-3722, or in Middletown at (513) 424-5351, ext. #3722.

News Release provided by Kathy Maurer.