Cow parsnip looks like something straight out of Jurassic Park, with its immense leaves and towering umbels of clustered white flowers. Its scientific name is even derived from Hercules, son of Zues, legend for his extraordinary size and power. Unsurprisingly, in the most ideal conditions, this unique beauty can reach up to ten feet tall - though it commonly tops out at half that size. Its gigantic leaves emerge in early spring and are a larval food source for many insects. Next come the thick hairy stalks that boast spectacularly huge spring to summer blooms that provide nectar to adult butterflies, bees and other insect pollinators. Please see safety note below.
- Plant type/canopy layer: deciduous, perennial, herbaceous plant
- Size at maturity: 3-10' high, 2-5' wide
- Light requirements: full sun to full shade
- Moisture requirements: moist to seasonally wet soil
- Bloom time: April - August (May - June in the Portland Metro area)
- Growth rate/ease: medium growth rate, very easy to grow
- Wildlife support: flowers attract and provide nectar to adult butterflies; overall plant is a caterpillar host plant and larval food source for native moths and butterflies
- Native habitat/range: found in open woods or forest edges, riparian areas, and other moist places at nearly all elevations from coast to alpine, across almost every county of the Pacific Northwest (and beyond). Portland Plant List - yes.
- Special features & uses: deer resistant; landscape uses include pollinator gardens, meadowscapes, raingardens and woodland gardens
What to Expect + Gardening with Cow Parsnip: This easy-breezy plant will be a dramatic and bold addition to your raingardens, moist pollinator gardens and/or open woodland gardens.- It tolerates most any amount of sunlight, but will flourish in moist, part sun/part shade areas. The summer drought will cause it to naturally die back until next year - but you can prolong its growth and bloom by providing supplemental moisture. This plant will readily spread by seed in ideal conditions, a trait that some may welcome while others find annoying. Cow parsnip has been in Sparrowhawk's partially sunny raingarden for nearly a decade and we've enjoyed seeing it spread easily within the raingarden. It stays in check because it is limited by lack of water in the summer drought (we do not provide any supplemental summer water). The ground goes naturally bone dry, the plants dry back by late-summer and pop up in some of the same places and some new places, from year to year.
IMPORTANT SAFETY NOTE: Cow parsnip contains chemicals that can cause skin irritation in individuals with sensitive skin. This reaction could occur if you're handling the plant in a way that breaks the tissues, like hand-pulling unwanted plants or harvesting edible leaves, thereby releasing its milky sap, especially from freshly cut stems. If you get the sap on your skin, then expose that skin to direct sunlight it can cause a rash known as photo-dermatitis. Thankfully, this isn't a plant that requires much tending and simply touching the surface, gathering seed, etc is not known to cause irritation. But you could play it safe and wear gloves when handling - especially if hand-pulling, pruning/cutting or harvesting. If you notice getting the sap on your skin, wash it off and avoid direct sunlight.
Photo Credit 2, 6: Nikkie West, Sparrowhawk Native Plants