Nasturtiums are annual plants that bring cheerful, vibrant color to any space, with flowers appearing in shades of yellow, orange, and red. Known for their unique, rounded foliage and trumpet-shaped blooms, the entire plant, including the leaves and flowers, is edible, offering a peppery zest to salads. These versatile, fast-growing plants are perfectly suited for container gardening, thriving in pots where they can be easily managed.
Preparing the Container and Medium
Selecting the correct container is the first step toward successful nasturtium cultivation in pots. A pot size of at least six to eight inches in diameter suits a single, bushy variety. Trailing types or multiple plants require a larger container, such as one 10 to 12 inches across, to accommodate their growth. All containers must have functional drainage holes to allow excess water to escape, preventing the roots from sitting in saturated conditions.
Nasturtiums perform best in a lightweight, well-draining potting mix. Use a high-quality, sterile potting mix instead of heavy garden soil, which compacts easily and impedes drainage. Avoid mixes that are overly rich or contain high amounts of nitrogen fertilizer, as this promotes foliage growth at the expense of flowers. Before sowing, fill the container, leaving about an inch of space below the rim, and thoroughly pre-moisten the medium until water drains from the bottom.
Planting the Nasturtium Seeds
Plant nasturtium seeds directly into pots once the danger of the last spring frost has passed. These plants are sensitive to cold and thrive when the soil temperature warms to 55° to 65°F. To encourage quicker sprouting, the large, tough-coated seeds can be prepared by soaking them in water overnight or by gently nicking the seed coat (scarification).
Nasturtiums have a delicate root system and dislike disturbance, making direct sowing into the final container the preferred method. Plant the seeds at a depth of \(1/2\) inch to 1 inch below the soil surface. For pots holding multiple plants, space the seeds eight to twelve inches apart, or sow them closer and plan to thin weaker seedlings later. Gently cover the seeds with potting mix and lightly pat the surface to ensure good seed-to-soil contact.
Post-Planting Care and Establishment
After planting, maintain consistent moisture to encourage germination, which typically occurs within seven to fourteen days. Keep the soil evenly moist but not waterlogged during this period to prevent seeds from rotting. Place the pots in a location that receives full sun, ideally six or more hours of direct sunlight daily, as this is necessary for robust blooming. Nasturtiums flourish in moderate temperatures, performing best between 60°F and 75°F.
Once seedlings emerge and develop their first set of true leaves, they may need thinning if sown too closely. Thinning involves carefully snipping the weaker seedlings at the soil line, leaving the strongest plants spaced appropriately for mature growth. After establishment, transition to a less frequent watering schedule, allowing the top inch or two of soil to dry out between applications. Nasturtiums are drought-tolerant and perform better when slightly stressed for water.
Nasturtiums require very little supplemental feeding, especially if the potting mix was not overly fertile. High-nitrogen fertilizers must be avoided, as they prioritize leafy growth at the expense of flowers. If growth appears stunted or weak, a single application of a diluted, balanced fertilizer or one formulated for blooming flowers can be applied mid-season. Providing full sun and slightly drier soil will ensure a season of abundant, colorful blossoms.