Here's a comprehensive guide to growing Glandularia bipinnatifida (Prairie Verbena) from seed in the USA:
Site Selection
Sunlight: Prairie Verbena thrives in full sun (at least 6 hours per day). It can tolerate some light shade, but flowering may be reduced.
Soil: Well-drained soil is essential. Prairie Verbena is highly adaptable to various soil types, including sandy, loamy, and clay, but it cannot tolerate soggy conditions. It prefers a slightly acidic to neutral soil pH.
Sowing Seeds Outdoors
Fall Sowing:
Sow seeds in late fall, after the first hard frost but before the ground freezes.
Prepare the soil by clearing any debris and lightly raking the surface.
Scatter seeds evenly over the soil surface.
Lightly cover seeds with a thin layer of soil (about 1/8 inch).
Water gently but thoroughly.
Seeds will germinate in the spring.
Spring Sowing:
Sow seeds after the last spring frost.
Prepare the soil as described above.
Sow seeds as described for fall sowing.
Keep the soil consistently moist until seeds germinate.
Starting Seeds Indoors
Timing: Start seeds indoors 8-10 weeks before the last expected spring frost in your area.
Stratification: Prairie Verbena seeds can benefit from cold stratification to improve germination rates. You can mimic this process by:
Mixing seeds with moist sand or vermiculite in a sealed container.
Refrigerating the container for 4-6 weeks.
Sowing:
Sow seeds in seed starting mix, about 1/8 inch deep.
Keep the soil moist and warm (70-75°F) until seeds germinate.
Transplanting:
Once seedlings have a few sets of true leaves, gradually acclimate them to outdoor conditions.
Transplant seedlings outdoors after the last spring frost, spacing them 6-12 inches apart, depending on the variety.
Planting Depth
Whether sowing seeds directly or transplanting seedlings, plant them at a depth of about 1/8 inch.
Watering
Keep the soil consistently moist until seeds germinate and seedlings are established.
Once established, Prairie Verbena is drought-tolerant and only needs watering during prolonged dry spells.
Stratification and Scarification
Stratification: As mentioned above, cold stratification is beneficial for Prairie Verbena seeds.
Scarification: Scarification (scratching or nicking the seed coat) is not typically necessary for Prairie Verbena seeds.
Maintenance Tips
Mulching: Apply a light layer of mulch around plants to retain moisture, suppress weeds, and regulate soil temperature.
Deadheading: Remove spent flowers to encourage more blooms and prevent self-seeding. However, leaving some seed heads in the fall provides food for birds.
Pest and Disease Control: Prairie Verbena is relatively pest and disease resistant. However, watch out for common problems like aphids, spider mites, and powdery mildew.
Invasiveness
Prairie Verbena is not considered invasive in most areas. However, it can self-seed readily in ideal growing conditions. If you want to prevent this, remove seed heads before they mature.
Additional Notes
Prairie Verbena is a native plant to North America and is a valuable addition to wildflower gardens, meadows, and naturalized areas.
It is a hardy perennial that can tolerate a wide range of growing conditions.
Prairie Verbena flowers come in various colors, including purple, pink, and white.
Remember to choose Prairie Verbena varieties that are suitable for your specific climate and growing conditions. With proper care, you can enjoy the beautiful and long-lasting blooms of Prairie Verbena in your garden for many years to come.
