Nasturtiums, with their vibrant flowers and unique lily pad-like foliage, are a favorite among home gardeners, offering both ornamental beauty and culinary uses. This popular annual plant is known for its fast growth and easy care, making it a rewarding addition to any sunny garden space. The cheerful blooms, which range from creamy yellow to deep mahogany, and the leaves both possess a distinct peppery flavor. They can be harvested for use in salads and garnishes, providing color, ground cover, or a cascading element in containers.
Timing the Planting for Success
The most important factor when planting nasturtium seeds is ensuring the danger of cold temperatures has completely passed. Nasturtiums are sensitive to cold and will be damaged or killed by frost, so direct sowing should only occur after the last expected frost date in your region, often waiting an additional one or two weeks for safety. The seeds germinate best when the soil has warmed, ideally maintaining a temperature between 60°F and 70°F. Planting into soil that is too cold will cause the seeds to rot before they can sprout.
Direct sowing the seeds into the garden is the preferred method for nasturtiums because the seedlings have fragile roots and are prone to transplant shock. For gardeners with very short growing seasons, starting seeds indoors is an option to gain a head start. Start the seeds four to six weeks before the last expected frost date, using biodegradable pots like peat or coir to minimize root disturbance during transplanting. When moving the young plants outdoors, it is necessary to harden them off slowly over a week to ten days to prevent shock.
Essential Planting Requirements
Nasturtiums thrive in a location that receives full sun, meaning at least six hours of direct sunlight daily, which encourages the most prolific blooming. While the plants can tolerate partial shade, too little light will result in a leggy plant with significantly fewer flowers. Nasturtiums perform best in poor to average, well-draining soil. Planting them in overly rich soil, especially one high in nitrogen, will promote lush foliage growth at the expense of flower production.
The large, easily handled seeds should be sown shallowly, about one-half to one inch deep in the soil. Spacing needs vary by variety; bushy or mounding types require about 8 to 12 inches of space, while vining or trailing types need 24 to 36 inches to spread or climb. To help speed up the germination process, which can take up to two weeks, the seeds benefit from a simple pretreatment. The hard seed coat can be slightly nicked with a nail clipper (scarification), or the seeds can be soaked in water overnight before planting. This helps water penetrate the tough outer layer.
Ongoing Care for Vigorous Growth
Once the nasturtium seedlings have established themselves, their maintenance needs are relatively minimal. Watering should be deep and consistent while the plants are young, but established plants prefer the soil to dry out somewhat between waterings. Overwatering is a common mistake that can lead to fungal diseases and root rot, which is why well-drained soil is important. Watering at the base of the plant in the morning also helps prevent fungal issues by allowing the leaves to dry completely.
Fertilization is generally unnecessary and can be counterproductive to flower production. If plants show signs of nutrient deficiency, such as pale leaves or stunted growth, a single, low-nitrogen fertilizer application may be used sparingly. Removing spent flowers, known as deadheading, encourages the plant to produce new blooms continuously instead of putting energy into seed production.
Nasturtiums are known to attract pests like aphids, which often settle on the new growth tips. A strong jet of water from a hose can dislodge the insects, or an insecticidal soap spray can be applied to manage the infestation. Pruning vining types is simple, requiring only the trimming of stems that become too long or unruly, which can also promote a bushier growth habit. The leaves, flowers, and immature green seed pods can all be harvested for consumption, offering a peppery zest to summer meals.