Published by Brian Wagner on 11/6/25 in “Growing Flowers from Seed.”
Verbena officinalis (commonly called vervain) is a short-lived perennial (or biennial) native to Europe and hardy to Zone 5, providing wonderfully delicate pink flowers in summer. It used to be referred to as an ‘herb of grace’ and has been cultivated for many centuries. Unlike its tropical relatives, V. officinalis bears small lilac flowers on wiry branched spikes and thrives in dry, open ground.
In its native geography it thrives primarily in the open grassland habitats of Europe, but can also persist in dry woodland settings where soil is thin and sunlight is somewhat dampened.
Growing from Seed
A landmark study by Brändel and Schütz (2003) has provided a lot of insight into the dormancy of the seeds. Basically, they seem to have a non-deep physiological dormancy but the seeds are quite sensitive to temperature. Get it wrong, and they might not work.
First, you need to cold stratify the seeds for 3 months. It may not take quite this long, but cold stratifying for this long (or even longer) has been the most effective at breaking dormancy. In nature, seeds come out of dormancy after a long, cold winter.
To germinate the seeds after cold stratification, however, you need to crank the heat – studies have used 25C (80F) during the day, coupled with cooler night temperatures (around 50F to 60F). These alternating temperatures seem to help quite a bit, i.e. when the nights are cooler than the days. Heat mat during the day, then switch it off at night. Also, they absolutely require light for germination – and they need to be surface-sown and uncovered, and provided with bright light for 8 hours/day.
If you try and germinate the seeds at cooler temperatures, around 15C (60F), this has been shown to actually push them into a kind of conditional dormancy. Fascinating study if you want to read it (Brändel and Schütz, 2003). What brings them out of this conditional dormancy? Heat and light.
You can also use warmer temperatures than this, such as 30C (90F) or even 35C (95F) – as long as you provide bright light.
Seeds are known to last a long time, even 7 years – so if the seeds aren’t germinating, you can try cold stratifying them again for 4 weeks – and then use a daytime temperature of 30C (80F) but keep the seeds really cool at night, around 4C (40F) (a fridge temperature), which has been shown to be effective at reducing the cold strat length.
Technical Write-Up
Seeds have a non-deep physiological dormancy (Baskin and Baskin, 2014; Brändel and Schütz, 2003; Liu et al, 2011). The landmark study by Brändel and Schütz (2003) provides strong insight into the seasonal and temperature-dependent behaviour around dormancy for this species. Cold stratification breaks dormancy (Baskin and Baskin, 2014; Brändel and Schütz, 2003; Grime et al, 1981; Liu et al, 2011; Woodward, 1997; Toscano et al, 2018; Carron et al, 2008). Seeds are dormant at dispersal as evidenced by Grime et al (1981) who tested fresh seeds with almost no germination at 20/15C. GA3 has not been effective at breaking dormancy (Abril-Saltos et al, 2017), but the overall behaviour of the seeds match the patterns typically seen with non-deep PD. The landmark study was done by Brändel and Schütz (2003) which showed that cold winters relieve dormancy, while high summer (especially fluctuating) temperatures induce germination. (The authors also found evidence of modest dormancy cycling between conditional dormancy and non-dormancy, but which cycling seems to dissipate over time.) The dormancy is therefore classified as a non-deep physiological dormancy. To grow from fresh seeds, it is important to induce the appropriate temperature regimens; failure to do so can result in failure. Seeds must be cold stratified for 12 weeks at 3C (Brändel and Schütz, 2003; Grime et al, 1981); Liu et al (2011) found success after just 40 days (at 4C). After cold stratification, the seeds must be incubated at 25C (80F) during the day and 15C (60F) at night (Brändel and Schütz, 2003). Note that the length of cold stratification required can be reduced to 4 weeks if the incubation temperatures have a wider differential between day and night (e.g., if night temperatures are 2C to 5C) (Liu et al, 2011; Carron et al, 2008). To achieve a large differential between day and night temperatures, it is suggested that heat mats (with a thermostat-controlled probe) are used during the day, and then seeds are placed in a residential fridge at night. Light is absolutely required for germination (Brändel and Schütz, 2003; Baskin and Baskin, 2014; Grime et al, 1981; Liu et al, 2011). Germination in the dark is possible at 15/5C (60/40F) but is not recommended as it is fickle (Brändel and Schütz, 2003). Seedlings may emerge as quickly as 3 days (Brändel and Schütz, 2003). Also, it is noteworthy to mention that smoke water has been shown to promote germination (Adkins et al, 1999). Lastly, with respect to dried seeds, it appears that seeds to experience some after-ripening, but that it may take a few years for this to bypass any cold stratification requirement (Tsitsilin and Kondratyeva, 2020). Seeds do seem to last at least 7 years (Ibid.), but it is still recommended that dried seeds are treated the same as fresh seeds.
References
Abril-Saltos R, Ruiz-Vásquez T, Alonso-Lazo J, Cabrera-Murillo G. Germination, seed diameter and pregerminative treatments in species with different purposes of use. Agronomía Mesoamericana. 2017 Dec;28(3):703-17.
Adkins SW, Davidson PJ, Matthew L, Navie SC, Wills DA, Taylor IN, Bellairs SM. Smoke and germination of arable and rangeland weeds. InSeed biology: advances and applications. Proceedings of the Sixth International Workshop on Seeds, Merida, Mexico, 1999. 2000 (pp. 347-359). Wallingford UK: CABI Publishing.
Baskin CC, Baskin JM. Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. Second Edition. 2014. Academic Press: San Diego, California
Brändel M, Schütz W. Seasonal dormancy patterns and stratification requirements in seeds of Verbena officinalis L. Basic and Applied Ecology. 2003 Jan 1;4(4):329-37.
Carron CA, Baroffio CA, Vouillamoz JF. Stratification methods for the germination of vervain. Revue Suisse de Viticulture, Arboriculture et Horticulture. 2008; 40(3): 195-199.
Grime JP, Mason G, Curtis AV, Rodman J, Band SR. A comparative study of germination characteristics in a local flora. The Journal of Ecology. 1981 Nov 1:1017-59.
Liu K, Baskin JM, Baskin CC, Bu H, Liu M, Liu W, Du G. Effect of storage conditions on germination of seeds of 489 species from high elevation grasslands of the eastern Tibet Plateau and some implications for climate change. American Journal of Botany. 2011 Jan;98(1):12-9.
Toscano S, Romano D, Tribulato A, Cavallaro V. Assessing and modeling seed germination of Mediterranean wildflowers for low input landscape restoration. Restoration Ecology. 2018 May;26(3):525-36.
Tsitsilin A.N., Kondratyeva T.N. Effect of storage duration and growth regulators on the sowing qualities of Verbena officinalis L. seeds. Proceedings of the Kuban State Agrarian University. 2020;(85):279–83.
Woodward FI. Life at the edge: a 14-year study of a Verbena officinalis population’s interactions with climate. Journal of ecology. 1997 Dec 1:899-906.