Ornamental Milkweeds To Try In Your Garden

By David Graper
SDSU Extension Horticulture Specialist

Swamp Milkweed (Asclpeias incarnate)

Swamp milkweed (Asclpeias incarnate) is native to the Great Plains, and is a great ornamental milkweed for your home garden. Don’t let the swamp milkweed name discourage you from trying this plant, you do not need a swamp to grow it, since it is a very adaptable plant. While it prefers average moisture conditions, it can tolerate periods of dry weather as well as some occasional standing water. It too is perennial but generally not as long-lived as butterfly weed.

Swamp milkweed grows taller, generally 3 to 4’ in height and does not spread out as much as butterfly weed, usually only about a foot. The flowers are pink and white and are produced mid-summer to fall, mostly at the ends of the upright stems while butterfly weed tends to produce flowers along gently arching stems. Swamp milkweed has a fibrous root system which makes it easier to transplant, but it is very easy to propagate it by seed as well. All sorts of butterflies and bees will flock to the flowers and Monarchs will readily use this plant as a food source for their larva.

Deadheading is recommended to keep the plants from spreading seed around the garden but I like to leave a few, just to keep some fresh new plants growing up. I also think that the opening seed pods are quite attractive as they expose their seeds and little fluffy attachment that allows the seed to be carried a great distance before it settles to the ground. If you end up with too many seedlings next spring, just pull out the ones you do not want or dig them up and share them with a friend. Swamp milkweed grows best in full sun to part shade.

Butterfly Weed (Asclepias tuberosa)

Butterfly weed (Asclepias tuberosa) is the 2017 Perennial Plant of the Year, a plant that is certainly deserving of this honor. But there are many other types of milkweeds, additional members of the Apocynaceae family, that a gardener might want to consider adding to their garden as well. There is also a huge diversity of other members of this family that make very interesting house plants.

Common Milkweed (Asclepias syriaca)

Common milkweed (Asclepias syriaca) was once an abundant plant found in road ditches, fence rows and CRP land across the Midwest and Great Plains. But reductions in CRP acreage as well as the removal of fence rows has dramatically reduced its numbers. Many believe that the marked decrease in Monarch butterflies is directly tied to the reduction in common milkweed populations. Like butterfly weed and swamp milkweed, common milkweed can be utilized in the garden. However, gardeners need to keep an eye on it since it spreads by rhizomes that will allow the plant to spread quite rapidly in the garden, given the chance. Common milkweed has a much coarser texture than the other two milkweeds with leaves that are about 4 to 5” long and about 2 to 3” wide. The stems are also quite large, allowing the plant to grow to 4’ or more. The rounded umbels of pink flowers begin to develop in mid-summer and will continue up until frost. Common milkweed can produce a lot of seed, so once again deadheading is recommended.

Of the three milkweeds, common milkweed probably would best be used in a more naturalized setting that has a bit more of a wild look. Its spreading habit can be troublesome in a more formal setting as new plants pop up from the thick rhizomes beneath the soil, making them a little difficult to manage. But if you had some area at the back of your lot where you could let a few plants “do their thing” the Monarchs and many other nectar-feeding insects would appreciate it.

Balloonplant (Gomphocarpus physocarpus)

Another interesting plant to try in your garden, that is also in this family of plants is Gomphocarpus physocarpus. It has many common names including balloonplant, balloon cottonbush, bishop’s balls or my favorite, fuzzy balls. I suspect that you have already gathered from all those common names that the plant produces something that looks like a ball or balloon, which in this case are the fruit, another follicle, similar to what we see in the other milkweeds. In fact, the species name physocarpus means “bladder fruit”.

Gomphocarpus is native to Africa and not hardy in our area, but it makes a great annual plant if you are looking for something that will grow 4 to 5’ tall with a 2 to 3’ spread, attract butterflies, be a food source for Monarch caterpillars and create a point of interest when you invite your gardening friends into your yard. The white flowers begin to appear in late summer and continue into the fall. The fuzzy, round, follicles usually grow to about 2” in diameter and may eventually ripen, split open and release seed if they are not damaged by frost before that time. The fruiting stems may also be cut and used as dried materials for fall bouquets.