How to Grow Nasturtiums
Beautiful, old-fashioned, edible nasturtiums will attract hummingbirds, butterflies, bees, and other beneficial insects. Easy to grow, nasturtiums have trumpet-shaped flowers range from brilliant hues of flaming orange and butter yellow, to cooler tones like rose and salmon, to subtle shades such as burgundy or cream with mahogany splashes.
Nasturtiums (Tropaeolum spp.) are native to South America, where they were used medicinally and for flavoring dishes. Imported to Spain in the late 1500s, these plants eventually graced gardens across Europe. Claude Monet, the impressionist artist, planted an arched main allée at his now-famous garden in Giverny, France, where he lived and painted from 1883 to 1926. Monet wanted a small fringe of flowers along the pathway’s edges, so he chose to grow what he believed to be dwarf nasturtiums (T. minus). Turns out they were ramblers (T. major) that crept far into the pathway. He liked the effect so much that he repeated it yearly. Today, Monet’s garden is a museum where nasturtiums grow as he loved them. Nasturtiums came to North America via Europe; Thomas Jefferson grew them at Monticello.
Dwarf nasturtiums make attractive edging. Semi-trailing types brighten flower baskets and window boxes. Single-flower climbers, with runners up to 8 feet long, are great for trellising.
Grow nasturtiums by sowing seeds directly in soil after your area’s last spring frost date. Poke the big seeds ½ to 1 inch deep into moistened, well-drained soil and firmly cover. Nasturtium seeds typically germinate within 10 days and may bloom within a month. Peppery edible nasturtiums don’t transplant well. If you’re starting them a few weeks early indoors, use biodegradable pots that you can bury without disturbing the roots. Some growers nick the hard seeds with a knife or sandpaper and soak them overnight to improve germination, but I’ve never needed this step for them to sprout.
Don’t over water nasturtiums after they’re established. Give them about an inch of water per week during dry periods. They flower best in full sun but will tolerate partial shade. Nasturtiums are heat wimps and will fade during hot spells. If this happens, cut them back, and they’ll usually return to brighten your autumn. I’ve enjoyed blooming nasturtiums alongside my ripening pumpkins.
Nasturtiums don’t need very fertile soil, especially regarding nitrogen, which brings more leaves and fewer blooms. Aphids love the soft plant tissue created by ample nitrogen, especially when other nutrients that would strengthen plant tissue are too low or missing.
Nasturtiums have a reputation for attracting aphids. They’re sometimes used as the sacrificial lamb to lure aphids from other plants. But if you don’t want to surrender your beautiful flowers, try these methods to control aphids.
Wash or squash. Check the underside of nasturtium leaves every few days and blast any aphids with water or apply organic insecticidal soap wherever you see them. Squash stubborn return visitors or clingy insects that water can’t dissuade.
Bait and wait. Advocates of this method use nasturtiums to attract aphids so that natural predators will move in to feast on the aphids and then stay to eliminate the insect pests for the rest of the season. Or, just as aphids show up in the garden, these folks purchase and release aphid predators, such as lacewing larvae or ladybugs. While some gardeners swear by this method, others say the predators take too long to arrive and the aphids spread to other crops, or the released predators abandon ship permanently after they devour the first aphid banquet.
The French decoction. I learned this French folk method while growing nasturtiums as edible flowers for restaurants. I didn’t want to use any insecticides or see any aphids — not even biological insecticides, and not even one aphid. So, I used this modified soil drench to strengthen my nasturtiums and make them less attractive to aphids.
First, I gathered as much horsetail (Equisetum arvense) as I could safely boil in water in a 2-gallon cooking pot for 30 minutes. While this mixture boiled, I gathered non-flowering stinging nettle (Urtica dioica) and stuffed a 5-gallon container half-full with it, then tossed in 2 handfuls of dried kelp. I poured the hot, boiled horsetail and its liquid into the nettle container, which I then filled with water from the garden hose. After it had infused and fermented for 3 days — with daily stirring — the resulting liquid was diluted to about a tenth of its original strength, and I used it as a soil drench to moisten the soil at planting time.
My bountiful nasturtiums rarely had aphids after I used the French decoction. Sometimes I dried nettle and horsetail in the spring for future use, and repeated the process in late summer. Other garden plants may benefit from this method, too, but keep in mind that the mixture encourages blooming — not a benefit for plants you want to remain leafy, such as lettuce.
Nasturtium flowers, leaves, and even seedpods are edible. The lovely flowers can be cut for entree garnishes or salad embellishments. The younger, more tender leaves will add spicy flavor to fresh salads and are reportedly high in vitamin C. You can even pickle the young, tender, green seedpods to make capers: Nasturtium Capers Recipe. Keep in mind that the flavor isn’t subtle — the word “nasturtium” comes from the Latin nasus tortus, meaning “nose twister.”
A salad spinner is great for preparing fresh nasturtium flowers and leaves for culinary uses. As a market gardener, I’d remove “field heat” from edible flowers immediately after picking by dunking them in cold water for 10 minutes. This keeps them fresh longer. Then I’d whirl them in the spinner to remove unwanted specks or wayward insects.
Nasturtiums have had a centuries-long relationship with kings, artists, presidents, and ordinary gardeners. Those of us who grow them today are continuing their story as a garden favorite for centuries to come.
Give these historic cultivars an honored spot in your garden. (Seed is available from Baker Creek Heirloom Seeds.)
• ‘Dwarf Cherry Rose’
• ‘Empress of India’
• ‘King Theodore’
• ‘Yellow Canary Creeper’ (pictured in slideshow)
Barbara Berst Adams is author of The New Agritourism: Hosting Community and Tourists on Your Farm. She has supplied edible nasturtiums to restaurants and writes for numerous gardening and farming publications.
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