Nasturtiums are a beautiful, edible, annual flower (which can be grown as a perennial in warm climates) that will add lovely bursts of color to your garden. A hummingbird and butterfly attractor, nasturtiums repel some harmful insects—including aphids—while attracting other pests—like slugs—to them, thus protecting your neighboring garden crops from attack. The leaves and flowers are commonly used as a garnish or in salads and have a mildly spicy taste, while the seed pods can be used as a capers substitute. Take note that, if growing conditions are right, nasturtiums can become garden bullies and invade the rest of your crops, so make sure to prune and deadhead if this becomes an issue.
Mahogany nasturtium grows 2–2.5″ deep red-colored flowers that form in a visible location above the foliage for a striking splash of color. Leaves are bright green, and plants will bloom beginning about 6 weeks from planting through to the fall. Fairly compact plants with cascading vines, these nasturtiums will do well in hanging baskets or containers.
Seed: To increase germination rates, seeds should be lightly nicked using a nail file. Rub the outer shell of the seed until you can see a tiny pinprick of lighter coloration. Additionally, putting seeds in the freezer for a few days before planting will help. You can also soak seeds in water before planting.
Seed Depth: 1/2″
Space Between Plants: 8–12″
Space Between Rows: 12″
Germination Soil Temperature: 55–65°F
Days for Germination: 10–14
Sow Indoors: 1–5 weeks before average last frost date.
Sow Outdoors: After danger of frost.
Vegetative: Can be propagated by taking stem cuttings, although they will grow better from seed. If you would like to grow from cuttings, select a piece of the plant with only a small amount of space between the leaves. Remove the lower leaves and place cuttings in a perlite-based medium. Keep the medium moist and transplant directly to the garden after a few weeks when roots have begun to form.
Grows best in a mild climate with sunny, cool summers and will grow back from their roots after light frosts. In fact, it can be grown as a short-lived perennial in USDA Zones 9–11. If you’re growing in an area with hot summers, partial shade will keep plants from overheating.
Natural: Full sun. Prefers afternoon shade in warm weather.
Artificial: As young nasturtiums in particular prefer full sun, HID lamps will be best for growing this plant indoors. Keep lamps at least 6″ from tops of plants to prevent burning, but close enough to keep soil temperatures at 55–65°F.
Soil: Prefers a well-drained sandy or loamy soil. A pH of between 6.5 and 7.5 will keep plants healthy and nourished. If soil is lower in nitrogen, plants will put out more blooms and less leaves.
Soilless: Germinate seeds in a soilless mix. As nasturtiums don’t love to be transplanted, use a compostable pot filled with mix if planning on moving them into your garden.
Hydroponics: Thrives in hydroponic systems and will do especially well using the NFT.
Aeroponics: Thrives in aeroponic systems.
Water: Requires moderate levels of water. For best flavor, consistent moisture is important, but take care not to overwater. Leaves and flowers will develop a stronger spicy taste if allowed to dry out between watering.
Nutrients: Requires low to moderate levels of nutrients. Greater levels of phosphorus and potassium are needed than of nitrogen. Excess nitrogen will result in a plant with many leaves but fewer flowers.
Pruning: If you don’t want your nasturtiums to become invasive and take over by reseeding, remove flowers before they mature and drop their seeds.
Pest(s): Nasturtiums will deter aphids, whiteflies, squash bugs, rabbits, and deer.
Deficiency(s): A lime deficiency may make nasturtiums more susceptible to attacks by insects, so if you are experiencing pest problems, test your soil for lime content.
Rotation: Alternating between nasturtium and beans or leafy greens can help keep disease down and soil nourished.
Companions: Grows well with cabbage, collards, kale, kohlrabi, broccoli, mustard, cucumbers, radishes, fruit trees, and herbs. Nasturtium is a helpful companion plant because it attracts some pests away from your other plants (acting as a trap crop), deters other pests (including caterpillars and squash bugs), and attracts predatory insects that prey on pests.
Harvest: Pick ripe, open flowers throughout the summer for culinary or decorative uses. Collect leaves at any time starting in early summer through the first frost, but don’t take more than 1/3 of the foliage in one harvest or you’ll risk stunting the plant’s growth. Gather young seed pods when they are still green and soft enough to be pricked with your fingernail. You can also wait and pick the mature brown seed pods for use as a pepper substitute.
Storage: Fresh leaves, flowers, and young seedpods will keep for up to 1 week in the refrigerator. Store dried seeds in a cool dark place for up to 1 year, grinding just before use for best results.
Fun Fact: The nasturtium originated in South America in the Andes mountains from Bolivia north to Colombia.
Preserve: You can pickle immature nasturtium seed pods either in a vinegar solution or lacto-fermented in brine. Mature seeds can also be dried and ground for use as a culinary spice. Leaves and flowers can be dried or ground into a paste and frozen mixed with oil or water. Flowers can also be steeped in vinegar to add some spicy flavor.
Prepare: Flowers and leaves are most often used to add a spicy flavor and wonderful color to salads. Young seedpods can be eaten raw but will have a very strong flavor. The pickled seedpods are used as a substitute for capers and can also be included in stir-fry recipes. Dried seedpods are ground and used as a black pepper alternative. You can find recipes for soups, main dishes, and desserts that incorporate the nasturtium plant.
Nutritional: Leave and flowers provide vitamin C and are a good source of antioxidants. The fiery tasting seeds are made up of 25% protein, though you probably won’t be eating much of them in one sitting.
Medicinal: All parts of the plant have medicinal uses. Leaves and flowers can be ground into a paste and used topically for treating minor wounds and skin irritation due to their antibacterial, antiseptic, and antifungal properties. It is also included in face washes and shampoos because it can help to rid your skin of pesky acne and make your hair grow faster and healthier. When leaves and flowers are consumed as a tea, you might expect benefits to respiratory, digestive, and urinary systems. Certain plant extracts are being studied for their anti-cancer properties.
Warnings: Flowers bought at a florist may have been treated with chemicals that you wouldn’t want to eat or put on your skin, so always grow your own!
Get out in the garden and pick some leaves and flowers for this Nasturtium and Tomato Salad with Dates and Pistacios