Nasturtiums are vibrant, easy-to-grow annuals prized for their bold, often peppery-tasting flowers and rounded foliage. They are commonly used as decorative borders, ground cover, or grown in containers, and both the leaves and blossoms are edible. USDA Hardiness Zone 8 is characterized by mild winters (10°F to 20°F minimum temperatures), resulting in an extended growing season. This climate is ideal for cultivating frost-sensitive annuals like nasturtiums for a long season of color and harvest.
Understanding Zone 8 Planting Timelines
Nasturtiums are sensitive to cold temperatures and will not survive a hard freeze, so outdoor planting depends on the final spring frost. In Zone 8, the average last frost date generally falls between mid-March and early April (March 13th to March 28th). Gardeners should wait until all danger of frost has passed and the soil temperature has warmed up before sowing seeds. For best germination, soil temperatures should be consistently above 55°F.
Planting seeds one to two weeks after the average last frost date is recommended to prevent damage from a late cold snap. The long, frost-free season in Zone 8 allows for successive planting, extending the blooming period into the fall. New batches of seeds can be sown every few weeks from the initial spring planting until mid-summer for continuous flowering. Starting seeds indoors is discouraged, as nasturtiums resent root disturbance and often experience transplant shock.
Seed Preparation and Site Selection
Before planting, preparation can significantly improve the rate of germination. Nasturtium seeds have a tough outer coat that delays water uptake. Gently nicking the shell with nail clippers or soaking the seeds in warm water for 3 to 12 hours will soften the coat and speed up germination. Discarding any seeds that float after soaking is common, as they are often not viable.
Site selection is important, as nasturtiums thrive in specific, less-fertile conditions. They perform best in full sun, receiving at least six hours of direct sunlight daily, though they tolerate partial afternoon shade in hotter areas. Most varieties prefer lean, average, or poor, well-draining soils. Planting in rich, highly fertile soil or adding excessive compost is counterproductive, as it encourages foliage growth at the expense of flower production.
Direct Sowing Methods and Spacing
Direct sowing the prepared seeds into their permanent location is necessary due to the plant’s delicate root system. The large seeds should be planted one-half to one inch deep into the prepared soil. This depth maintains moisture while allowing the seedling to push through.
Spacing depends on the variety chosen. Bush or dwarf types can be spaced 6 to 10 inches apart. Vining or trailing cultivars require a wider berth of 10 to 12 inches to accommodate their growth. After covering the seeds with soil, the area should be thoroughly watered. If multiple seeds germinate, the weaker seedlings should be carefully thinned out to the proper spacing once they have established true leaves.
Ongoing Maintenance for Nasturtium Success
Once established, the care regimen focuses on watering and pest management. Nasturtiums require consistent moisture until fully established, after which they are somewhat drought-tolerant. Water only when the top layer of soil has dried out. Overwatering must be avoided, as wet conditions can lead to fungal issues and root rot.
Fertilization is generally unnecessary and can be detrimental to flowering, especially with high-nitrogen feeds. High nitrogen promotes leaf growth, diminishing flower production. Common pests are aphids, which are particularly attracted to nasturtiums, sometimes leading to their use as a “trap crop.” Regular harvesting of flowers and deadheading spent blooms encourages new growth and prolongs the overall display.