Nasturtium

The edible flower that earns two keeps: a peppery salad crop and the garden's best-known aphid trap crop, from a plant almost impossible to kill.

Direct sow the big seeds 1/2 inch deep after frost - they hate being transplanted - into lean soil and full sun.

Direct sowing is the only method worth bothering with: nasturtiums have brittle roots and sulk or die when transplanted. The seeds are large and easy to handle — poke them 1/2 inch deep, 10-12 inches apart, once frost has passed and soil has warmed to 55°F or more. Soaking them overnight first softens the tough coat and speeds a sometimes-slow, 7-14 day germination. They'll bloom in about six to eight weeks.

The one rule that trips people up: keep the soil lean. Rich, fertilized ground grows enormous leaves and hides the flowers. Full sun gives the most bloom, though they tolerate part shade (with fewer flowers) and even prefer it in hot climates.

Water moderately, never feed, harvest often, and let them do their pest-trapping work.

Care is mostly about restraint. Water evenly and moderately, letting the surface dry between; skip fertilizer entirely. Harvest leaves and flowers frequently — it keeps the plant tender and pushing new growth. Guide climbing types onto netting or a fence early; bush types need nothing.

Then let them be a trap crop. When aphids pile onto the nasturtiums (they will), that's the system working: the pests are on the decoy instead of your cabbages. Hose down or pull the worst-infested plants before the colony rebuilds and spreads, and encourage the ladybugs and hoverflies that the aphid buffet draws in.

Pick leaves and flowers all season for the plate; pickle the green seeds as capers.

Everything above ground is harvestable. Pick flowers fully open in the morning for salads and garnish; snip leaves young and tender for a peppery green (they toughen and go papery with age); and gather the plump green seedpods while still soft. Harvest often — the more you take, the more the plant makes.

The seeds are the sleeper crop: pickled green in vinegar and salt, they become poor man's capers, a sharp, briny substitute that's arguably better than the real thing. Leave the last flush of seeds to ripen and drop, and nasturtiums usually reseed themselves for next year.

Everything is best fresh - flowers wilt within a day; pickled seeds keep for months.

Nasturtium flowers are a same-day ingredient: they wilt within hours of picking and keep only a day or two refrigerated in a container with a damp paper towel. Leaves hold a few days like other tender greens. The one thing that stores well is the pickled seed — green pods packed in a hot brine of vinegar, salt, and spices keep for months in the fridge and are ready to eat after a few weeks. Dried ripe seed, kept cool and dark, stays viable for 2-3 years for replanting.

The easiest seed you'll ever save: big seeds that self-sow on their own or store for years.

Nasturtiums are a perfect beginner seed-saving crop. Each flower forms a cluster of three big, knobbly seeds that are impossible to lose. Let the last flush ripen on the plant until they fall away brown and dry, gather them off the ground, dry another week indoors, and store cool and dark — they keep 2-3 years. Open-pollinated types come true; even mixes give you a fun spread of colors.

Left alone, they self-sow reliably in mild climates, popping up as volunteers exactly where last year's plants dropped seed. In cold zones the frost kills the parents but the fallen seed often overwinters and sprouts on its own in spring.

A genuine leafy green: high in vitamin C, with the peppery mustard oils (glucosinolates) that give it both flavor and mild antimicrobial reputation.

Unlike most edible flowers, nasturtium is real food. The leaves are a legitimate leafy green — notably high in vitamin C (the old name 'Indian cress' and its watercress-like bite are both clues) — and rich in the same mustard-oil compounds (glucosinolates) found in cabbage and cress that give the peppery heat.

Those mustard oils are behind nasturtium's folk reputation as an antimicrobial and respiratory remedy. Eat it as the fresh, vitamin-rich green it is; the pepper concentrates in the leaves, mellows in the flowers, and peaks in the seeds. Moderation is sensible — a lot of raw mustard oil can upset a sensitive stomach.

Peppery leaves in salad, jewel-toned flowers as garnish or stuffed, green seeds pickled as capers.

Nasturtium is a working kitchen plant, not just a garnish. The flowers — brilliant orange, red, and yellow — go into salads whole, get stuffed with soft cheese, or top a plate for color and a mild pepper note. The leaves bring a sharp watercress bite to salads and blend into a peppery pesto that stands in for basil. The green seeds, pickled, become the famous poor-man's capers.

Pair the heat with something rich or sweet — goat cheese, buttered bread, ripe tomatoes. The whole plant is at its best raw and just-picked; cooking mutes both the color and the peppery character that make it worth growing.

A real folk remedy behind the flavor: the mustard oils have documented antimicrobial activity, though it's food first.

Nasturtium has a more credible herbal history than most edible flowers, and it traces to the same chemistry as its flavor. The glucosinolate-derived mustard oils (notably benzyl isothiocyanate) have measurable antibacterial and antifungal activity in the lab, and traditional European herbalism used nasturtium leaf and flower for respiratory and urinary infections — a use that still appears in some modern herbal preparations combined with horseradish.

Keep it in perspective: this is a nutritious peppery green with mild, evidence-supported antimicrobial compounds, not a treatment. Enjoy it as food that happens to carry a genuine kernel of its folklore, and eat it in normal culinary amounts.

No flowers means soil too rich; aphids are expected (that's the point); mildew comes from crowding.

Lush leaves, no flowers: the classic nasturtium problem — soil is too rich or over-fertilized. Stop feeding; poor soil is what triggers bloom. Aphids everywhere: expected, and often desirable — the plant is doing its trap-crop job; hose them off or remove the worst plants to protect the crops nearby. Chewed leaves: cabbage-white caterpillars, which also prefer nasturtium to your brassicas — pick them off. White powdery leaves (powdery mildew): crowding and age; thin, improve airflow, resow. Poor germination: the seed coat is tough — soak overnight and be patient. Wilting in heat: above ~90°F flowering stalls; give afternoon shade and water.

Brought from Peru to Europe in the 1500s, named for a Roman trophy pole, and a wartime pepper substitute.

Nasturtiums are native to the Andes of South America (Peru through Colombia), where the flowers were eaten long before Europeans arrived. Spanish explorers carried them home in the 1500s, and the plant spread through European gardens as both ornament and salad crop — the English called it 'Indian cress' for its cress-like bite.

The odd Latin name Tropaeolum comes from the Greek for 'trophy': the round leaves and helmet-shaped flowers reminded Linnaeus of the shields and helmets Romans hung on a trophy pole after a victory. During both World Wars, the peppery pickled seeds served as a home-garden substitute for hard-to-get capers and black pepper — the same trick worth reviving today.

A cool-season-loving annual: cold zones grow it all summer; hot zones grow it in the mild shoulders with shade.

Zones 3-6: a summer annual — direct sow after frost for bloom from early summer until the first fall freeze, which ends it; a second sowing in mid-summer refreshes the show for autumn. Zones 7-8: long seasons; spring-sown plants often fade in peak heat, so sow again in late summer for a strong fall flush. Zones 9-11: flip the calendar — nasturtiums are a cool-season (fall-through-spring) crop here, since heat and humidity above ~90°F stall flowering and invite mildew; give afternoon shade and grow them out of the worst summer months. In frost-free areas they can behave as short-lived perennials, but most gardeners treat them as reseeding annuals everywhere.