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
Note: If you want to know if it occurs in your county, follow this PLANTS database link and zoom in on your state.
The Water Parsnip Plant:
The Water Parsnip plant is in the carrot family (Apiaceae), along with many of the plants that feed the Black Swallowtail caterpillars. It naturally grows in wetlands, in shallow water near ponds, or in ditches. The plant prefers sandy or “mucky” soil, but it is not picky and can grow in other soil types as long as it is moist. If growing in moist soil, it will initially grow as a basal rosette. If growing in standing water, it will initially grow as clusters of aquatic leaves. After the initial stage, it grows between 2 and 6 feet tall!
Water Parsnip obviously loves the water, but don’t let that deter you from planting it in your garden. We’ve successfully grown it in a container with frequent watering. While it is best to plant in moist areas or near water, it will happily grow in an average garden as long as you water during dry spells.
Do you have a low lying area that doesn’t drain well and is too moist for fennel? That is the perfect area for Water Parsnip! The Black Swallowtail and Anise Swallowtail caterpillars will love it!
Plant Sium suave for Hungry Caterpillars
Since Sium suave grows quickly, it easily feeds hungry Anise and Black Swallowtail caterpillars. Add this native host plant to your butterfly garden and watch the beauty of the butterfly life cycle.