By Julie Christensen
What annual flower thrives in poor soil, delights in neglect and produces profuse blossoms through most of the summer? Nasturtiums, of course. These humble flowers were discovered in the jungles of Peru in the 16th century. They made their way to Europe with Spanish explorers and quickly gained popularity for their fast growth and beauty. During King Louis XIV’s reign, food was scarce in France and people relied on the edible leaves and flowers of nasturtium as a food source. Later, during the Victorian Era, people throughout Europe ate nasturtium, which is high in vitamin C, to combat scurvy.
Today, nasturtiums are grown mostly for their ornamental value, although the flowers are still added to salads. Nasturtiums make excellent companion plants in the vegetable garden because they are said to deter squash bugs and other garden predators.
Planting Nasturtium Outdoors
If you’d like to try nasturtiums (Tropaeolum majus), you can start with nursery transplants in the spring. But, like many annuals, nasturtiums are incredibly easy to grow from seed. Save your money for hard-to-grow perennials instead.
Nasturtium seeds are large, as seeds go, and resemble pea seeds or even pebbles. They have a wrinkled, hard outer coating. To soften the seed coat and hasten germination, many gardeners soak the seeds for a few hours in warm water or even nick the seed coat with a file.
Sow nasturtiums outdoors after the last expected frost. They grow best in well-drained, slightly dry soil. They tolerate both alkaline and acidic conditions and don’t need much in the way of nutrients. In fact, too much fertilizer or overly rich soil encourages lush green growth at the expense of blooms. Space the seeds 4 to 6 inches apart for a lush display. Planting guides suggest nasturtium grows in full sun and partial shade, but in most climates, you’ll get the best blooms in full sun. Partial shade is suitable in very hot, dry regions.
Starting Nasturtium Seeds Indoors
If you prefer, start nasturtium seeds indoors 6 weeks before the last frost. Starting seeds indoors is a good choice if you want to grow nasturtiums in pots or containers. Another reason to start them indoors is to encourage early blooming.
To start seeds indoors, plant them ½ an inch deep in a light, soil-less starting mix. Nasturtiums don’t transplant well, so use peat pots that you can plant directly in the ground. Spray the starting mix with water and keep the mix evenly moist. Store the peat pots in a warm location, such as on top of a refrigerator or near a radiator. Move young seedlings to a sunny window and transplant them outdoors when they stand 6 inches high.
Although nasturtiums repel many garden pests, they do attract aphids. In most cases, aphid infestations are heaviest in spring and rarely cause serious damage. To control aphids, spray the undersides of the leaves with a brisk stream of water several times per week. If that doesn’t do the trick, use insecticidal soap or oil. Apply these products on cool, cloudy days and thoroughly coat each leaf. Re-apply oil or soap every 7 days, or according to package directions.
Nasturtiums rarely require deadheading, but you can trim the plant back in late summer if it looks straggly or blooming slows. Although rare, pale leaves might indicate a nutrient deficiency. Apply a bit of all-purpose fertilizer, according to package directions. While nasturtiums prefer slightly dry conditions, they don’t tolerate drought. Water at least once per week to keep the soil slightly moist. Water containers more frequently.
Nasturtiums are wonderfully versatile plants, and you’ll find one for every gardening condition. Compact varieties work well in pots or intermingled with other annuals. Bush varieties are larger and look nice in a mixed border. Try trailing or climbing nasturtiums in containers or scrambling over walls and rock gardens. Below are just a few varieties worth trying:
- Alaska Series: These plants have a bushy, compact form and dense, variegated foliage. The flowers appear atop of the leaves.
- Apricot Trifle: A low, mounding plant with dark green foliage and large apricot blooms.
- Canary Creeper (T. Peregrinum): This unusual nasturtium is actually a perennial vine. The bright yellow flowers resemble a bird, hence its name.
- Climbing Spitfire: This common variety produces vivid orange blooms and long trails of bright green foliage. Train it along a trellis or add it to containers.
- Whirlybird Nasturtium: This is one of the most colorful and first to bloom varieties of nasturtium.
For more information visit the following sites:
Nasturtium: A Favorite Old-Fashioned Flower from the University of Vermont Extension
Garden Nasturtium from Cornell University Extension
Learn more about other easy to grow edible flowers on our site.
When she’s not writing about gardening, food and canning, Julie Christensen enjoys spending time in her gardens, which includes perennials, vegetables and fruit trees. She’s written hundreds of gardening articles for the Gardening Channel, Garden Guides and San Francisco Gate, as well as several e-books.