The spicy, peppery, flavors of arugula, nasturtium, and cress have been rediscovered in recent years. Now they’re featured in popular mesclun salads at pricey restaurants all over the United States. The great news for gourmet gardeners is that these bold flavors can be harvested practically year-round in many parts of the United States. These herbs will add an unexpected zing to a wide variety of foods, and are high in many important nutrients including vitamin C and calcium.
Traditional Italian arugula (Eruca vesicaria) stormed the American culinary scene a decade ago, weaving its continental flair into salads and pastas across the country. A relative of mustard, arugula (also called rocket or roquette) has toothed, elongated, dark-green leaves that are generally eaten raw and impart what some describe as a nutty but sharp flavor. When cooked into soups, stews, and other foods, the taste is more reminiscent of other cruciferous vegetables. Arugula has become one of the most popular additions to both pre-mixed greens, available in grocery stores and farmer’s markets, and in packets of seed mixes.
Small bundles of the herb alone are sometimes commercially available, but arugula is one of the easiest plants to grow. It provides a bountiful crop in just a few weeks. This cold-hardy annual can be planted in early spring in average soil with average moisture. Leaves can be harvested at any time. Two-inch shoots are as delicious as 6- to 8-inch leaves. Some gardeners plant successive two-week crops from spring through fall, but arugula does best when the weather is cool, turning stronger in flavor and having a tendency to bolt in hot weather. Early spring and late-summer plantings are best, and harvesting larger leaves from the outside of the plant and pinching off the flower stalks in cut-and-come-again fashion will extend the harvest for many weeks. The small purple-striped, cream-colored blossoms are also edible but tend to get hidden in most foods. Because the prolific and delicious greens provide more salad fixings, pinching off the flower buds to encourage more leaves is preferable for culinary purposes.
Arugula self-sows well in Zone 5, returning reliably in early spring, and it is a successful candidate for fall planting. It also makes a great container plant, easy to grow and ferry in and out to extend the harvest.
As arugula’s popularity grew, so did the panache of other pungent greens. The common garden nasturtium (Tropaeolum majus or T. minus), also known as Indian cress, has only recently made its way onto modern dinner tables, but its hot, radish-like flavor was a much-favored accompaniment of bygone eras. Our ancestors commonly consumed both the leaves and flowers tossed in salads, stuffed with small fish, or infused in a beautiful, peach-hued vinegar. Recipes for pickling the buds as a substitute for capers date back to the sixteenth century. The Shakers considered nasturtiums to be a staple vegetable and planted the vines in rows where they were supported with stakes, which was believed to produce a more bountiful crop.
As commercially grown produce became more readily available, the utility of the nasturtium was forgotten, but a savvy group of produce growers have renewed interest in the prolific blooms as an edible commodity. Nasturtiums are currently available seasonally in major markets.
Undemanding and easy to grow, nasturtiums never lost their aesthetic appeal for the home gardener. They are currently one of the most popular of all edible flowers and one of the most versatile plants in an edible landscape. Many varieties provide gardeners a choice of compact or trailing growth habits in many colors. Nasturtiums, particularly today’s hybridized varieties, are known for their prolific growth.
Nasturtiums are cold-sensitive annuals that flourish through the warm summer days, providing piquant flowers and greens long after the arugula is past its prime. Color is an indication of pungency. Old-fashioned yellow varieties are milder in flavor than the ubiquitous orange, and the red can be extremely hot.
Like most plants, nasturtiums thrive in well-prepared soil with some organic matter. To harvest more flowers, go easy on high-nitrogen fertilizers, which encourage heavy leaf growth and fewer flowers. Soak the seeds before planting them outdoors in May or after all danger of frost is past. Sow them 1/2 inch deep, spaced 6 or more inches apart.
Year-round watercress (the true nasturtium)
Barely distinguishable in flavor from the common garden nasturtium, watercress (Nasturtium officinale) has significantly different growth patterns and habitat. Watercress grows wild in almost every state and can be gathered practically year-round as far north as Pennsylvania, where its glossy leaves can be harvested as long as its water source doesn’t freeze. But beware of gathering wild greens because of the danger of poisonous look-alikes and polluted waters. You’re better off growing it yourself if you can or buying it fresh in the supermarket.
The highlight of 1950s finger sandwiches, watercress lost favor as American women went to the workplace and abandoned such delicacies. Currently, interest in watercress is increasing somewhat due to its popularity in Asian cuisine, and it is commercially available in most major markets. Store watercress by trimming the stems and placing them in a glass of water; cover loosely with a plastic bag, and set it in the refrigerator. Outstanding flavor and an impressive nutritional profile, which includes significant amounts of vitamin C and calcium, make watercress worthy of a resurgence in popularity.
Sometimes cultivated in streams, watercress can also be grown successfully as a container plant. Because the natural habitat is cool, flowing water with at least some sun, that is the environment you’ll want to create at home. Start seeds in trays and keep them in a cool room or cold frame at about 50°F. Make sure that they remain moist until ready to transplant. For containers, plant the starts in limed potting soil in a clay pot placed in a pan of water. Keep the plants moist by adding fresh water to the saucer several times a week. Not letting the standing water stagnate is critical. Watercress takes five to six months to mature, but once established is easy to regenerate from cuttings. It also reseeds after the second year, but flowering plants are more bitter than first-year growth. Watercress can withstand very cold conditions and can remain outside as long as its water source doesn’t freeze.
Many types of cress grow wild throughout the United States. In contrast to the moisture-loving watercress, these relatives of the mustard family grow wild in dry, open fields and vacant lots. Despite their weedy growth characteristics, these plants provide fabulous greens for salads and sandwiches and are ready for harvest in as little as two weeks. Some are available from seed suppliers, who have culled the more palatable varieties for home gardeners.
Pepper grass (Lepidium sativum), also known as garden cress and curly cress, was a favorite with the pioneers, who ate the greens and used the crushed seed pods as a substitute for pepper. However, it has never gained favor with modern Americans. Its rapid growth-and-bolt cycle make it too fast for most edible landscapes, but it’s a natural for vegetable gardeners eager for a quick fix in the early spring.
The sharp-flavored, frilly leaf is a spicy accompaniment or alternative to lettuce. Use it as a bed for meats or vegetables, snipped over soups, tossed in all types of raw salads, or layered in sandwiches. Sprouted cress, which is traditionally mixed with mustard sprouts, provides a year-round source of vitamins A and C, as well as thiamin, niacin, riboflavin, and calcium.
Pepper grass is so easy to grow that the Dutch used to grow it on clay figurines called “cress-pigs,” no doubt the precursor of the popular chia pets of the 1960s. Like arugula, this cold-season crop is best in spring or fall. Although it is a wasteland plant, it grows well in typical garden soil with average water. It can be grown from seed sown in the garden 1/4 inch deep. Sow the seeds thickly as the foliage is sparse.
When the plants are about 2 inches tall–after about three weeks of growth–snip the top growth and the base will quickly produce another crop of leaves. Both pepper grass and arugula are subject to flea beetles, which can be sharply deterred with daily applications of hot pepper and garlic spray.
There is no mistaking the culinary appeal of pungent radish flavors. So similar are the flavors of arugula, nasturtium, and the cresses that they can generally be used interchangeably. In addition to adding them raw to salads and sandwiches, you can puree them with oil, mayonnaise, or butter and add to hot foods. They are especially complementary with potatoes, grains, and seafood.
Both watercress leaves and nasturtium leaves and flowers were traditionally served alone between slices of buttered bread. Dried nasturtium pods and pepper grass seed were both a Victorian substitute for pepper. All have been a popular salad green in some country at some time.
But the true beauty of these spicy plants is their availability to the home gardener through three seasons of the year (or year-round if you include container planting and indoor sprouts). They add a nutritional boost and flavor burst unequaled by your average lettuce.
Debbie Whittaker is a culinary herbalist in Denver, Colorado, where she teaches herb classes and lectures on sustainable cuisine.