Sow Clarkia on the surface of cool, drained soil where the plants will flower. Seeds need light. Seedlings resent a move.
Sow on the surface, in cool soil
| Factor | Recommended | Avoid |
|---|---|---|
| When | As soon as soil can be worked; fall in mild winters | Waiting until the ground is summer-warm |
| Depth | Press seed onto the surface; a dusting at most | Burying seed so it never sees light |
| Where | The bed or pot where plants will bloom | Pricking out a taproot from a module tray |
| Spacing | Thin to about 8 to 12 inches | A jammed ribbon that mildews |
Sow lightly on the surface; the seed needs light to germinate, and 8 to 10 inches of space once plants are up. [1] In an eastern garden, lightly rake seed in as early as March. [2] Cool soil is the point. Waiting until the bed feels like summer often means flowers open into the collapse. Two sowings two to three weeks apart can stretch a cool spring without pretending July will cooperate.
Should I cover Clarkia seed?
No. Press it onto firm soil. A dusting of fine grit is the most you should add. Deep cover stops germination.
How to sow Clarkia seed
C. amoena and C. unguiculata take the same surface sow. Scatter, press, keep the surface moist, then thin. [3]
- Rake a fine, drained seedbed in full sun (or afternoon shade in heat). Do not load the strip with manure.
- Scatter seed on the surface and press it in. Do not bury it.
- Mist to keep the surface evenly moist until sprouts show, then ease off. A hard jet washes seed into clumps.
- Thin to about 8 to 12 inches so air moves. Snip extras; pulling can loosen neighbors. Label the strip so you do not weed the seedlings as unknown greens.
Direct sow vs a plug, and what fails
Sow in place in spring or fall. Plants are drought-tolerant once up; do not over-water. [4] If you bought a plug, plant it young with the root ball intact — do not hold it in a tray until it is rootbound. Failures are buried seed, a hot late sow, and pricking out seedlings. C. purpurea and C. williamsonii follow the same rule.
Can I transplant Clarkia seedlings?
They dislike root disturbance. Direct sow where they will flower. A plug only works if you set it out young, soil and all.
If a late indoor tray is already stretching, sow a fresh strip outside instead of forcing a transplant.
FAQ
When should I sow Clarkia seed?
As soon as the soil can be worked in spring, or in fall where winters stay mild. Waiting for summer warmth often means bloom into heat collapse.
Can I start seed indoors?
Possible but clumsy. If you must, use a deep, plantable cell and set it out young. Direct sow is sturdier.
Will Clarkia self-sow?
Sometimes, if you leave pods to ripen and do not mulch the bed into a mat. Treat volunteers as a bonus, not a guarantee.
How far apart after thinning?
About 8 to 12 inches. Crowded ribbons mildew and flop faster than an airy strip.
Related guides
Recommended plants
References
- [1] NC State Extension Gardener -
https://plants.ces.ncsu.edu/plants/clarkia/ - [2] University of Arkansas Division of Agriculture -
https://www.uaex.uada.edu/yard-garden/resource-library/plant-week/farewell-spring-7-15-11.aspx - [3] Outsidepride -
https://www.outsidepride.com/resources/planting/clarkia-planting/ - [4] University of Washington -
https://depts.washington.edu/propplnt/Plants/clarkia%20amoena.htm
This note is part of Clarkia Guides.
More notes on making another plant live in Propagating Guides.
Updated: Reviewed by Bosquelle Editors