Water Parsnip (Sium suave) Quick Facts:
Host plant to Anise and Black Swallowtails
Hardy in USDA zones 3 to 8
Partial to full sun
Moist to wet soil (even standing water)
Native to most of North America
Umbels of small white flowers, blooms July to September
Grows 2-6’ tall
Space 2-3’ apart
60-day cold stratification or fall/winter sow
Fast grower after germination
Note: Even though Water Parsnip is native in most states, it isn’t found in every county of each state. It is naturally found around water like streams, ponds, and wetlands. If you want to know if it occurs in your county, follow the PLANTS database link and zoom in on your state.
Plant Water Parsnip Seeds for Hungry Caterpillars
Water Parsnip is a host plant to the Black Swallowtail and Anise Swallowtail butterflies, whose hungry caterpillars will feast on the the leaves until they are large enough to form a chrysalis. In the photo to the right, there are 6 little caterpillars gathered around the flowers. Thankfully, the plant is large enough to support them all!
The seeds need 60 days of cold stratification or fall/winter sowing. Surface sow and lightly press the seeds into the soil. Keep the soil moist!
Have patience with these seeds. Even though you’ll have to wait for winter or your 60 day cold stratification to end, Sium suave grows quickly once it germinates. As it easily feeds hungry Anise and Black Swallowtail caterpillars, it is worth the wait. Add this native host to your butterfly garden and watch the beauty of the butterfly life cycle.