Nasturtium

Tropaeolum sp.
Annual

Quick-growing summer annuals can add nearly instant color to your garden beds and planters. Nasturtiums (Tropaeolum spp.) produce yellow, orange and red flowers, usually on the same plant. These annual flowers grow readily from large seeds, so you can plant plenty of them with minimal effort and cost.

Nasturtium is both a decorative garden annual as well as a useful culinary herb.  There are two types of nasturtium; a trailing type (Tropaeolum majus) that can be trained to climb or allowed to spread on the ground and a bush type (Tropaeolum minus) that forms loose mounds.  Nasturtium produces colorful flowers all summer and has attractive water lily-like foliage. Nasturtium provides a peppery flavor similar to watercress.  It is useful as a plant for garden beds as well as for containers.

Culture

Nasturtium prefers a full sun location but will tolerate some light shade however flowering may be reduced.  Average well-drained garden soil produces the best growth.  Because nasturtium does not transplant well, it is suggested to directly sow seeds into the garden after danger of frost is past. If you must start seeds of nasturtium flowers and then transplant them, use peat pots which can be planted into the ground without disturbing the roots of the growing nasturtium seedling.

Plant the seeds 1/2-inch deep and space them 3 inches apart. The soil will require watering so the top 6 inches remains moist. Seeds take 10-14 days to sprout. The hard, dry seed coating on large nasturtium seeds can slow germination because it's difficult for water to soak into the seed and force it from dormancy. Germination of seed can be enhanced by soaking seeds overnight in water prior to planting or by gently rubbing the seed with a nail file to aid germination.

Once the nasturtiums sprout, thin the plants so they have 8 to 10 inches of space on all sides. If your plants begin to look leggy and produce fewer flowers during hot summer days, cut them back and they'll produce new growth and a second crop of flowers.

For the tastiest leaves, keep plants well watered as this helps to moderate the spiciness of the leaves and flowers. Heat stressed plants often produce leaves and flowers that may be more pungent than most people prefer. If plants show signs of decline or become leggy during the summer, cut them back lightly and they will produce new growth for the remainder of the season.

Seed viability: 3 - 5 years

Invasiveness

Although nasturtiums can make excellent additions to your garden, the plants may spread and are listed by the state of California as potentially invasive. To ensure that your nasturtium plants stay in bounds and don't spread into surrounding areas, locate them in beds surrounded by edging that extends several inches into the soil. To control self-seeding and further discourage spreading, pinch off drying flowers before they can set seed and remove plants with their roots intact at the end of the season.

Harvesting

Both the leaves and flowers can be harvested for use throughout the season.   Young leaves are most tender and flavorful.  Nasturtium flower buds and immature seed pods are also edible and have been likened to capers when pickled. Leaves and flowers can be stored in plastic bags in the refrigerator.   

Use

Use in green salads, potato salads, egg dishes and seafood dishes as well as vinegars.  Flowers used as edible decorative elements to foods.  Flavor is peppery. 

Popular Varieties

Many common varieties of nasturtiums are dwarf plants (Tropaeolum minus) that have a bushy, compact growth habit, making them quite useful in border plantings or for the front portion of a garden bed. Dwarf nasturtiums also make attractive additions to window boxes or patio pots. Dwarf cultivars include "Peach Melba," with creamy flowers that have throats of raspberry red; "Strawberries and Cream," with pale yellow flowers that have splashes of rosy pink and red; and the "Whirlybird" mix, producing bushy plants with a variety of flower colors that include salmon, yellow, orange and cream.