Introduction & History

Nasturtium arrived in Europe from the Andes in the 16th century and promptly colonised every cottage garden it touched. Its round, water-repelling leaves inspired the Latin name — nasturtium means 'nose-twister,' a nod to the peppery kick that makes the leaves, flowers, and unripe seeds all edible. Monet grew cascades of them at Giverny; wartime gardeners pickled the green seeds as a caper substitute. Few plants deliver so much colour, flavour, and pest-trapping utility for so little effort.

History & Origin

Native to the Andes from Colombia to Bolivia, where wild species scramble through mountain scrub. Introduced to Spain in the 1560s and quickly spread through European gardens. Thomas Jefferson grew them at Monticello. The Incas used the leaves medicinally; European herbalists adopted similar uses. Tropaeolum majus is the most widely cultivated of about 80 species in the genus.

Botanical Description

Sprawling or climbing annual with peltate (shield-shaped) leaves on long petioles, giving the foliage a distinctive parasol look. Flowers are spurred, 3–6 cm across, in shades of cream, yellow, orange, red, and mahogany, often with contrasting throat markings. The entire plant is succulent, smooth, and slightly waxy. Dwarf cultivars form compact mounds to 30 cm; trailing types reach 2–3 metres.

Planting & Cultivation

Sow seeds 2 cm deep directly after the last frost date — the large seeds are easy to handle. Nick the seed coat with a file or soak overnight for faster germination (7–12 days). Space 25–30 cm apart. For climbing types, provide a trellis, fence, or let them scramble through shrubs. Nasturtiums resent transplanting; direct sowing is best.

Cultivation Details

The golden rule: poor soil and some neglect. Rich soil and heavy feeding produce a mountain of leaves with few flowers. Water only during extended dry spells. Nasturtiums actually flower best when slightly stressed. Pinch growing tips on trailing varieties to encourage branching. In hot climates, plants may flag by midsummer — a hard cut-back and a soak can trigger autumn regrowth.

Climate & Hardiness

Tender annual killed by frost. Thrives in zones 2–11 as a warm-season plant. Ideal growing temperature 15–25 °C. Above 30 °C flowering slows and aphid pressure increases. In frost-free zones 10–11 it may self-sow and persist year-round but often becomes leggy. Cool coastal climates suit it perfectly.

Seasonal Care

Spring: sow after last frost. Early summer: enjoy first flowers, begin harvesting leaves. Midsummer: monitor for aphids, pick flowers regularly to prolong bloom. If plants look heat-stressed, cut back to 15 cm. Autumn: collect ripe seeds (they drop when brown), pickle green seeds. First frost ends the show — pull spent plants to the compost.

Propagation

By seed only — nasturtiums do not root reliably from cuttings. Seeds are large and foolproof. Collect when they turn from green to tan and fall from the plant. Store dry; viability lasts 4–5 years. Self-sowing is common in sheltered gardens. Some double cultivars set less seed; save favourites deliberately.

Diseases & Pests

Aphids are the primary pest — nasturtiums are famous trap crops that lure blackfly away from beans and brassicas. Accept some aphid presence on the sacrificial plants or blast with water. Caterpillars of the large white butterfly may shred leaves. Leaf miners create winding tunnels in leaves but rarely kill plants. No serious diseases; excessive moisture can cause stem rot at the base.

Culinary Uses

Everything tastes of watercress with a mustardy bite. Toss leaves into salads, layer flowers on open sandwiches, stuff blossoms with herbed cream cheese, or scatter petals over pasta. Pickled green seeds substitute for capers in tartare sauce and salsa verde. The flowers freeze beautifully in ice cubes for summer drinks. A peppery pesto made from leaves is surprisingly good.

Medicinal & Aromatherapy

Rich in glucosinolates, the same compounds that give brassicas their cancer-fighting reputation. Traditional use includes treating urinary tract infections, coughs, and skin conditions. The plant contains a natural antibiotic substance (benzyl isothiocyanate). In Germany, a nasturtium-horseradish combination is a licensed herbal medicine for respiratory infections. Generally safe but avoid large medicinal doses during pregnancy.

Container & Companion Growing

Container Growing

Dwarf varieties like 'Alaska', 'Jewel Mix', and 'Empress of India' are perfect for pots and window boxes. Use a lean, well-drained mix — avoid rich compost. A 20 cm pot per plant is sufficient. Trailing types cascade beautifully from hanging baskets. Water when dry; feed sparingly or not at all.

Companion Planting

One of the best companion plants in any garden. Use as a trap crop for aphids near beans, cucumbers, and squash. The sprawling habit suppresses weeds as living mulch. Plant under apple trees to deter woolly aphids. Nasturtiums also attract beneficial hoverflies. Keep away from fennel, which inhibits many companions.

Common Mistakes to Avoid

Feeding too much — rich soil gives all leaf and no flower. Starting seeds indoors in tiny pots (they hate root disturbance). Ignoring aphids until the colony is massive — either accept them as trap-crop duty or intervene early. Planting climbing types without support, resulting in a ground-level tangle. Confusing ornamental Tagetes with nasturtiums.

Harvesting & Preservation

Leaves, flowers, and green seeds are all edible. Pick leaves young for the mildest flavour. Harvest flowers mid-morning for the best appearance. Green seed pods can be pickled in vinegar with salt as 'poor man's capers' — they keep for months in the fridge. Flowers do not preserve well; use fresh. Seeds can also be dried and ground as a pepper substitute.

Frequently Asked Questions

Seasonal Care Calendar