Nasturtium

Nasturtium (Tropaeolum majus) is native to the Andean regions of South America, ranging from Bolivia and Peru to Colombia.

• First encountered by European explorers in the 16th century during Spanish expeditions to the New World
• Introduced to Europe in the late 16th century; by the 17th century it was widely cultivated in European gardens
• Spanish physician and botanist Nicolás Monardes wrote about the plant in 1569, describing it as a novel ornamental from Peru
• The double-flowered cultivar 'Hermine Grasshof' was among the most popular varieties in Victorian-era gardens
• Today, nasturtiums are cultivated on every continent except Antarctica, thriving in temperate to subtropical climates

Nasturtium is a bushy to trailing annual herbaceous plant, typically growing 30–60 cm tall in compact forms, with trailing varieties reaching up to 2–3 meters in length.

Stems:
• Succulent, fleshy, and round in cross-section
• Trailing or climbing varieties use their leaf petioles to twine around supports
• Stems are smooth, hairless, and pale green

Leaves:
• Peltate (shield-shaped), with the petiole attached near the center of the leaf blade rather than the margin
• 3–15 cm in diameter, round to slightly reniform
• Margins are entire and slightly wavy
• Upper surface is smooth and waxy, with prominent radiating veins
• Leaves display a distinctive water-beading property — water droplets form perfect spheres and roll off the surface (the "lotus effect")

Flowers:
• Solitary, borne on long peduncles arising from leaf axils
• 2.5–6 cm in diameter, with five petals arranged in bilateral symmetry
• Colors range from bright yellow through orange to deep scarlet and mahogany red
• The upper two petals are slightly smaller and often streaked; the lower three petals are larger and may have darker markings at the base
• A prominent nectar spur (calcar) extends from the back of the flower, 2–3 cm long, containing nectar to attract pollinators
• Flowers are protandrous — the male stage precedes the female stage, promoting cross-pollination

Fruit & Seeds:
• The fruit is a schizocarp that splits into three single-seeded segments (mericarps) at maturity
• Each mericarp is ~1–2 cm, pea-sized, and wrinkled when dry
• Seeds are large, round to ovoid, and pale brown
• A single plant can produce dozens of seeds per season

Nasturtiums thrive in warm, sunny conditions and are remarkably adaptable to poor soils, often blooming more prolifically in lean, sandy soils than in rich, heavily fertilized ground.

Light:
• Prefer full sun (6+ hours of direct sunlight per day)
• Can tolerate partial shade, but flowering is significantly reduced

Soil:
• Adaptable to a wide range of soil types, from sandy to clay
• Prefer well-drained soil with a pH of 6.0–7.5
• Excessively fertile soil promotes lush foliage at the expense of flowers

Pollination:
• Primarily pollinated by hummingbirds (in the Americas) and long-tongued bees
• The elongated nectar spur is an adaptation to bird and long-tongued insect pollinators
• Some varieties are self-fertile and will set seed without pollinators

Companion Planting & Pest Ecology:
• Widely used as a "trap crop" in organic gardening — aphids are strongly attracted to nasturtiums, drawing them away from more valuable crops
• The pungent compounds (mustard oil glucosinolates) released by the plant act as a natural deterrent to many herbivorous insects
• Attracts beneficial predatory insects such as hoverflies and ladybugs that feed on aphids
• Commonly planted alongside tomatoes, cucumbers, squash, and brassicas as a companion plant

All above-ground parts of the nasturtium plant — leaves, flowers, and seeds — are edible and nutritionally valuable.

• Leaves are exceptionally rich in vitamin C, containing approximately 130 mg per 100 g (comparable to parsley)
• Flowers contain the carotenoid pigment lutein, which supports eye health
• Both leaves and flowers contain glucotropaeolin, a glucosinolate that breaks down into benzyl isothiocyanate — a compound with documented antimicrobial properties
• Seeds are high in protein and contain erucic acid
• The peppery flavor is due to the same class of sulfur-containing compounds found in mustard, horseradish, and watercress

Nasturtium is generally considered non-toxic and safe for human consumption.

• The pungent compounds (isothiocyanates) may cause mild gastrointestinal irritation if consumed in very large quantities
• Individuals with kidney disorders or those on blood-thinning medications should exercise caution due to the high vitamin K content
• The plant is non-toxic to cats and dogs according to major animal poison control databases
• Some sources recommend avoiding excessive consumption during pregnancy due to the emmenagogue (menstruation-stimulating) properties traditionally attributed to the plant

Nasturtium is one of the easiest annual flowers to cultivate, requiring minimal care and rewarding gardeners with rapid, abundant blooms.

Light:
• Full sun is ideal (6–8 hours of direct sunlight)
• Partial shade is tolerated but reduces flowering

Soil:
• Well-drained, moderately poor to average soil
• Avoid heavy fertilization — too much nitrogen produces lush foliage but few flowers
• Suitable for containers, hanging baskets, raised beds, and ground cover

Watering:
• Moderate watering; allow soil to dry slightly between waterings
• Drought-tolerant once established, but prolonged dry spells reduce blooming
• Avoid waterlogged conditions, which can cause root rot

Temperature:
• Optimal germination temperature: 13–18°C
• Frost-sensitive; plant after the last frost date in spring
• Thrives in temperatures of 18–27°C
• Will die back with the first hard frost in autumn

Propagation:
• Direct sow seeds outdoors after the danger of frost has passed
• Seeds benefit from soaking in warm water for 12–24 hours before sowing to speed germination
• Sow seeds 1–2 cm deep, spaced 15–30 cm apart
• Germination occurs within 7–12 days
• Does not transplant well due to fragile, fleshy roots — direct sowing is strongly recommended

Common Problems:
• Aphids — the most common pest; can be managed with a strong spray of water or by encouraging natural predators
• Caterpillars of the cabbage white butterfly may feed on leaves
• Bacterial leaf spot in overly humid conditions
• Poor flowering — usually caused by over-fertilization or insufficient sunlight

Nasturtium is a remarkably versatile plant with applications spanning ornamental horticulture, culinary arts, and traditional medicine.

Ornamental Uses:
• Popular bedding plant for borders, containers, and hanging baskets
• Trailing varieties are excellent for covering fences, trellises, and embankments
• Used as ground cover in permaculture and food forest designs
• Attracts pollinators and beneficial insects to the garden

Culinary Uses:
• Flowers are used as edible garnishes in salads, appetizers, and cocktails
• Leaves add a peppery, watercress-like flavor to salads and sandwiches
• Unripe seed pods can be pickled in vinegar as a caper substitute ("poor man's capers")
• Flower buds can be used similarly to capers

Traditional & Medicinal Uses:
• Used in traditional Andean medicine as a remedy for urinary tract infections and respiratory ailments
• The antimicrobial compound benzyl isothiocyanate has been studied for its antibacterial and antifungal properties
• Historically used as a natural antibiotic and expectorant in European folk medicine
• Applied externally as a poultice for minor skin irritations and hair loss in some traditions