Sow cow parsnip in fall so winter cold breaks the seed's dormancy, or set a nursery plant with room for the taproot. Wear gloves when you handle seed heads and plants.
Sow in fall so winter cold breaks the seed's dormancy
| Factor | Recommended | Avoid |
|---|---|---|
| When | Sow outdoors in late fall, on moist ground that will freeze | Do not sow dry seed in warm spring soil and expect a quick stand |
| Depth | Barely cover, about a quarter inch, or press the seed in and dust with mix | Do not bury the seed an inch deep |
| Indoor path | Soak seed three days, changing the water daily, then cold-moist stratify about 100 days at 34 to 38 F | Do not skip the soak; inhibitors in the seed coat block germination |
| Handling | Wear gloves when you collect ripe heads or thin seedlings | Do not strip seed heads with bare hands in bright sun |
Cow parsnip multiplies by seed, not by stem cuttings. The seed has a deep dormancy, so the simple home method is to sow it in late fall on a weed-free, moist spot and let winter do the work. [1] Keep the surface from drying in spring. Germination may wait until warm days, and some seed waits a second year.
- Choose a moist bed in sun or part shade, with about three feet of room for each mature plant.
- Sow in late fall. Barely cover the seed, about a quarter inch, or press it in and dust it with mix so it still sees a little light.
- If you missed fall, soak fresh seed for three days, changing the water each day, then keep it cold and moist for about 100 days in the refrigerator before you sow. [2]
- Keep the spot moist after sowing. Do not let a spring drought bake the seedlings.
- Wear gloves when you collect brown seed heads in late summer, and store extra seed cool and dry.
Can I sow cow parsnip in spring?
Only after a three-day soak and about 100 days of cold, moist stratification. Untreated spring sowing often sits until the next year.
Set a nursery plant with room for the taproot
A plug or bare-root plant flowers sooner than seed, often in the first or second year, because the rosette is already built. [3] Set it in spring or fall while the soil is workable, and leave the taproot where it is once it is in. The season plan for moisture and gloves is on How to Grow Cow Parsnip. [4]
- Wear gloves and long sleeves. Cut roots and stems leak sap.
- Dig a hole as deep as the root mass and about twice as wide, in moist soil.
- Set the crown at soil level. Do not bury the growing point, and do not leave it perched high and dry.
- Give each plant about three feet of room so the leaves can open without sitting wet against a neighbor.
- Water it in, then keep the soil moist through the first growing season. Do not lift and move an established taproot later.
Should I divide an old clump?
No. This plant keeps a taproot and is short-lived. Sow fresh seed, or plant a new nursery start, instead of splitting the crown.
If nothing comes up the first spring, the seed may be waiting on a second winter. Keep the spot moist, and do not dig up the taproot once it is in.
FAQ
Can I grow it from cuttings?
No. Cow parsnip is grown from seed, or from a nursery plug. Stem cuttings are not a reliable home method.
How long until it flowers from seed?
Usually the second summer. Year one is a rosette. A nursery plug can flower sooner because that first year is already done.
Related guides
Recommended plants
References
- [1] Prairie Moon Nursery -
https://www.prairiemoon.com/heracleum-maximum-cow-parsnip - [2] Native Plant Network -
https://npn.rngr.net/renderNPNProtocolDetails?selectedProtocolIds=apiaceae-heracleum-5 - [3] Michigan State University Extension -
https://www.canr.msu.edu/nativeplants/uploads/files/Common_cowparsnip.pdf - [4] NC State Extension -
https://plants.ces.ncsu.edu/plants/heracleum-maximum/
This note is part of Heracleum Guides.
More planting notes by plant are gathered in Planting Guides.
Updated: Reviewed by Bosquelle Editors