How to Grow Nasturtiums from Seed: Complete North American Guide

Last updated: July 12, 2026

Before You Grow Nasturtiums

Nasturtiums (Tropaeolum majus) break almost every rule of ornamental gardening. Most annuals reward rich soil, regular fertilizer, and prompt deadheading; nasturtiums reward the opposite — poor soil, no fertilizer, and being left alone. Amend a bed generously and side-dress with balanced feed, and you get a spectacular mound of round, water-repellent leaves with almost no flowers. Nitrogen-rich soil sends nasturtiums entirely into leafy growth, because the biological trigger for flowering is mild nutrient stress. Poor soil produces flowers; rich soil produces foliage — the single principle everything else in this guide builds on.

Nasturtiums also do three jobs at once. As an ornamental, they are among the fastest-blooming annuals available — 35–52 days from direct sowing to open flower — which makes them as practical in a Zone 3 prairie garden as in a Zone 9 coastal one. As an edible, every part is usable: flowers in salads, peppery leaves in wraps, and unripe green seeds pickled as a caper substitute. As a companion plant, they act as a true aphid trap crop, one of the most effective biological pest tools a home gardener has. Understanding all three turns nasturtiums from a cheerful filler into an intentional, productive part of the garden.

Nasturtium Varieties: Bush, Trailing & Climbing Types

Growth habit matters more for nasturtiums than seed packets usually make clear. Bush and compact types form a tidy, rounded mound that stays within its space — ideal for containers, the front of a border, or anywhere you want coverage without sprawl. Tom Thumb is the classic compact type: genuinely small at 25–30 cm and one of the fastest to bloom in the category. Alaska Mix adds value beyond flower colour — its leaves are variegated with cream-white marbling, giving interest even before bloom. Trailing types are a different plant in practice: they don’t climb by tendrils the way morning glory does but sprawl and scramble, sending stems 90–180 cm in every direction. That makes them the choice for running through a vegetable bed, trailing over a basket edge, or draping a fence base. They are also the most effective type for companion planting, because the greater spread radiates volatile compounds and the trap-crop effect across a wider area.

Double-flowered nasturtiums — Gleam Mix, Whirlybird, and their relatives — sit between compact and trailing in both height and habit. Their distinction is bloom form: where standard nasturtiums carry five petals in a symmetrical ring, double types layer extra petals into the centre for a fuller, ruffled flower that holds up well when cut. Whirlybird types also have no nectar spur, which opens them to short-tongued bees and a broader range of pollinators than spurred types, which limit nectar mostly to bumblebees and hummingbirds. All three growth habits are open-pollinated, so saved seed reproduces true to habit — though flower colour mixes freely wherever several colours grow together.

What Nasturtiums Need to Flower

Nasturtiums flower best in average to poor, well-drained soil that is low in nitrogen and gets full sun. They evolved in the lean, rocky highlands of the Andes, and their needs still reflect it. The nitrogen relationship is the single most important fact about nasturtium culture: nitrogen drives vegetative growth, and in a plant primed to flower under mild stress, feeding it is the surest way to grow enormous leafy plants with almost no blooms. Don’t add compost to nasturtium beds. Don’t fertilize. Don’t plant them in the bed you spent three weekends amending with aged manure — a rich, deeply worked vegetable bed is exactly the wrong site for nasturtiums you want to flower. Plant them in the rougher parts of the garden instead: the edge of a path, a strip of lean soil along a fence, or a container of plain peat-perlite mix with no added feed.

Full sun is the preferred condition, but nasturtiums tolerate partial shade more gracefully than most sun-loving annuals — especially afternoon shade in hot climates, where it can extend the bloom window by easing heat stress on developing buds. In Zones 3–6, full sun all day is ideal and speeds the already-fast run to flower. Water needs are minimal once plants establish: nasturtiums are drought tolerant after the first two to three weeks, and overwatering during establishment causes more trouble than dry soil. In heavy clay with poor drainage, rot at the taproot is the most common early-season failure — fix the drainage rather than the fertility. In sandy soil they are almost impossible to kill. The whole growing philosophy fits in one line: treat them like a weed, and the less you do, the better they perform.

How to Grow Nasturtiums from Seed

Nasturtiums develop a pronounced taproot soon after germination, and that taproot is sensitive to disturbance. Where most annuals lose a week or two to transplant shock, nasturtium transplants often stall for three or more weeks while the damaged root re-establishes — and rarely catch up to a direct-sown neighbour in the same bed. For almost all of North America, direct sowing after last frost is both simpler and better. An indoor start begun four weeks early may still be recovering from transplant shock while the direct-sown plant is opening its first flower. The detailed seed germination guide covers soil-temperature management if you want the full mechanics.

Direct Sowing Nasturtium Seeds Outdoors

Direct sow nasturtium seeds outdoors after your last frost, once the soil has warmed to 10–15°C (50–60°F). Cold, wet spring soil rots the large seeds before they can sprout, so wait for genuine warmth rather than the calendar.

In early-spring sowings in Zones 5–6, covering the bed with black plastic for two weeks beforehand pulls soil temperature up to the germination threshold faster than air alone. In Zones 5–7, two sowings three weeks apart — May 1 and May 22, for example — send a rolling wave of fresh plants into bloom just as the earlier ones start to fade.

Starting Nasturtium Seeds Indoors in Short-Season Zones

Start nasturtiums indoors only in Zones 2–3, and only in biodegradable pots planted whole so the taproot is never disturbed. For everyone else the transplant stall cancels out the head start. The one real case is a Zone 2–3 gardener growing trailing varieties in a 90–110 day season, where every week counts.

The timing math is forgiving even at the cold edge. At 35–45 days to first bloom for bush types, a Zone 3 grower in central Manitoba who direct sows June 1 — after the ground has truly warmed — sees bush nasturtiums in full flower by mid-July, with continuous colour into early October before killing frost. That is a 10–12 week window from a single sowing.

Growing Nasturtiums in Cold, Humid & Arid Climates

Nasturtiums behave like three different plants depending on climate — a short-season prairie garden, a humid Mid-Atlantic summer, and a low-desert region where sowing “after last frost” drops seedlings straight into killing heat. Find your climate below and adjust timing to match.

Nasturtium Planting Calendar by Zone

Nasturtium sowing windows shift dramatically across North America. An early-June sowing is right for Zone 2 Saskatchewan but far too late for Zone 9 California, where the spring window opens in January and the fall planting is the primary season.

Caring for Nasturtiums Through the Growing Season

Watering & Feeding Nasturtiums

Water nasturtiums steadily only for the first 2–3 weeks after germination; once they flower, water only during extended dry spells. The early weeks matter most, while the taproot is establishing and the plant is most vulnerable. Water deeply once or twice a week during that period — enough to wet the soil to 15 cm (6 in) deep — then ease off as plants mature. Established plants in average soil usually need water only in dry stretches of 10–14 days without rain. In containers, check the top 2–3 cm every few days in summer and water when it is dry. In humid climates — the Southeast, Gulf Coast, and Pacific Northwest — water at the base rather than overhead, since wet foliage feeds the aphid colonies nasturtiums attract and promotes fungal leaf spot in warm, still air.

Do not fertilize nasturtiums during the season. The instinct to feed a plant producing only foliage is exactly wrong here — all-leaves-no-flowers almost always means excess nitrogen, from rich native soil, compost added at planting, or mid-season feed. Stop feeding entirely and let the soil nitrogen draw down; flowering usually resumes within two to three weeks. The only exception is containers, where nutrients leach quickly. Even then, use a dilute phosphorus-dominant feed (tomato food at one-quarter the label rate) no more than once a month — phosphorus supports flowering without the vegetative flush nitrogen triggers.

Deadheading & Pinching Nasturtiums

Deadhead spent blooms every 4–5 days to keep nasturtiums flowering into late season. Left alone, nasturtiums set seed prolifically and slow their flowering as energy shifts toward seed. Removing each spent flower along with the developing pod behind it, at the junction with the stem, delays seed set and holds the plant in continuous bloom. For the last two to four weeks of the season, stop deadheading and let pods mature — gathered when they turn from green to pale tan, those seeds store for next year or fall to self-seed in place. Pinching young plants helps too: remove the growing tip above the second or third leaf node when plants reach 15–20 cm (6–8 in) to force lateral branching and a bushier plant with more stems to flower, which is especially valuable for bush types in containers.

Managing Trailing Nasturtiums & Self-Seeding

Trailing nasturtiums in vegetable beds need occasional direction rather than cutting back. Lift a stem heading the wrong way and lay it where you want it; pin a stem to the soil with a small stone or wire and it will root at the nodes, thickening ground-level cover. In a vegetable bed the goal is to run trailing stems along the edges and between larger crops, not to let them smother low plants like lettuce or radishes — keep them at the perimeter and redirect any that creep too far in. Self-seeding is one of the plant’s most useful habits in established gardens: allow a few plants to seed and volunteer seedlings reliably return the following spring, effectively making nasturtiums a self-perpetuating annual you never have to repurchase once established.

Companion Planting with Nasturtiums

Nasturtiums protect vegetables through two mechanisms: an aphid trap crop and a volatile pest repellent. The first is the trap crop effect — aphids are powerfully drawn to nasturtium foliage and colonize it in preference to most neighbouring vegetables. A ring of nasturtiums at the edge of a squash bed, along a cucumber row, or at the base of a brassica patch creates a concentrated aphid reservoir you can monitor and knock back with a water jet, rather than finding a dispersed infestation across the whole garden. The second mechanism is chemical: the volatile glucosinolates in nasturtium foliage directly repel cucumber beetles, squash bugs, and whiteflies, which works independently of the trap crop and lowers colonization pressure even where aphids aren’t the main concern. The strongest deployment uses both at once — trailing nasturtiums at the bed perimeter, releasing repellent compounds while pulling aphids away from the crops that matter. For the wider picture, the vegetable companion planting chart maps how every crop pairs across the garden.

Nasturtiums have no meaningful allelopathic effect — they don’t release root exudates that suppress neighbours — which makes them unusually flexible. They can be inter-planted in rows, tucked between crops, or grown as a dense border without chemical conflict. The two practical cautions are light (tall trailing stems can shade very low crops if planted on the south side) and late-season aphid spillover: as nasturtiums decline in fall, the aphids they’ve been hosting may move to nearby brassicas, so keep a 45–60 cm buffer between fading nasturtiums and fall kale, broccoli, or cabbage. Paired with French marigolds and calendula, nasturtiums round out a layered annual companion system covering aphids, beetles, nematodes, and pollinators at once.

Harvesting & Eating Nasturtiums

Harvesting Nasturtium Flowers & Leaves

Nasturtium flowers and leaves taste peppery and bright — like a sharper watercress — and hold their flavour in both raw and cooked dishes. The flowers carry a floral edge and are used regularly in restaurant kitchens because the flavour survives in a dish rather than fading. The leaves share the bite but stronger: young tip leaves are milder and good in salads, while mature leaves carry more heat and work in wraps, sandwiches, or as a watercress substitute. Both are high in vitamin C and contain glucosinolates with documented antimicrobial activity. Harvest flowers in the morning once dew has dried, picking fully open blooms rather than buds or wilting past-peak flowers. Rinse gently — the petals bruise easily — and, stored between layers of barely damp paper towel in the fridge, fresh flowers keep for two to three days.

Strip leaves from the stem at the petiole rather than cutting the stem, which preserves the branching. The round, water-repellent leaf makes an attractive platform for canapés as well as a salad green, and stuffed nasturtium flowers piped with a little cream cheese or herbed chèvre are a standard farm-to-table appetizer that takes about three minutes to assemble. Only harvest from plants that have not been treated with pesticides or synthetic fertilizers; if any spray has touched the garden, wait out the product’s stated re-entry interval before eating.

Cooking with Nasturtiums: Pesto & Infused Vinegar

Beyond salads, the two most useful ways to put a glut of nasturtiums to work are pesto and infused vinegar. For nasturtium pesto, blitz a packed cup or two of leaves and flowers in place of basil with garlic, toasted nuts (pine nuts, walnuts, or pumpkin seeds), hard cheese, and olive oil — the result is herbal with a distinct radish-like bite, and it goes onto pasta, toast, sandwiches, roasted vegetables, or a baked potato exactly where basil pesto would. Stems can go in too; they carry the same peppery flavour. For infused vinegar, pack a sterilized jar with flowers and leaves, warm white wine or cider vinegar until it steams (not boiling), pour it over to submerge them, and steep two weeks in a cool, dark spot before straining. The vinegar turns peppery and lightly coloured and lifts salad dressings, slaws, and anything that wants a sharp splash.

Pickling Nasturtium Seeds into Capers

The most underused nasturtium food is the green seed pickled as a caper substitute — the classic “poor man’s capers.” Pickled nasturtium seeds have a briny, peppery flavour comparable to imported Mediterranean capers, with a texture that holds in cooking and a sharper bite many cooks prefer. Timing is everything: harvest the seeds while green and still firm, about the size of a small pea, before they pale toward cream and develop the hard coat of a mature seed. The window lasts roughly a week per cluster, so pick frequently through midsummer as the plant sets seed continuously. Once seeds pale from green toward cream, they are too mature and turn unpleasantly hard when pickled.

The method is simple. Bring a brine of 120 ml (½ cup) white wine or cider vinegar, 1 teaspoon salt, and ½ teaspoon sugar to a boil. Rinse the green seeds, pack them into a small sterilized jar, pour the hot brine over to cover, tap out air bubbles, seal, and cool before refrigerating. Refrigerator-pickled nasturtium capers are ready in 5–7 days and keep up to three months; for shelf-stable jars, process in a boiling water bath for 10 minutes and they hold up to a year. Use them anywhere you’d use capers — pasta puttanesca, chicken piccata, smoked salmon, devilled eggs, or stirred into aioli.

Growing Nasturtium Microgreens Indoors

Nasturtium seeds grown as microgreens give a peppery, mustard-like shoot ready to cut in 14–16 days, indoors and year-round. The same open-pollinated seed you sow in the garden doubles as a fast winter crop on a windowsill, which makes a packet useful long after the outdoor season ends. Because the seeds are large and hard-coated, soak them 8–12 hours first, then sow them thickly across a tray of moist, plain potting mix and press in without burying. Keep the tray at room temperature — 18–21°C (65–70°F) — under a bright window or grow light, and mist to hold even moisture. The shoots emerge with the plant’s signature round leaves and are best cut with scissors at 5–8 cm (2–3 in), once the first true leaves open, for the fullest peppery flavour. Nasturtium microgreens carry the same vitamin C, iron, and glucosinolates as the mature plant and bring a broader, rounder heat than sharp radish shoots — excellent on salads, sandwiches, tacos, and as a garnish.

Saving Nasturtium Seeds

Let the three-lobed seed clusters ripen on the plant until they turn from green to pale tan and pull away easily by hand. Nasturtiums are among the easiest plants in the garden to save seed from. All types — bush, trailing, and double-flowered — are open-pollinated, and seed stores well with germination that holds for three to five years. Leave selected blooms well past their visual peak, until the petals dry and drop and the seed structure behind them feels slightly papery; the seeds separate freely from the plant when fully mature. Don’t rush it — seed gathered while still green won’t germinate reliably. Spread the harvest on a paper plate or screen for another one to two weeks of drying before storage.

The key point on fidelity is that growth habit saves true but flower colour does not. Seed from a trailing variety produces trailing plants and seed from a bush variety produces bush plants, but because nasturtiums are heavily insect-pollinated, bees mix colour freely wherever several colours grow together. Saved seed from one orange plant in a mixed bed will throw a range of oranges, yellows, reds, creams, and bi-colours next season — a pleasant result for most gardeners, since a self-seeding bed gradually settles into a shifting mixed-colour population that needs no further purchase. To keep a colour line true, isolate that variety at least 30–50 m (100–150 ft) from other nasturtium colours, or hand-pollinate and bag the blooms as they open. Store dried seed in labelled paper envelopes inside a sealed glass jar in a cool, dark place; viability holds well for three years and declines noticeably in years four and five.

Troubleshooting Nasturtium Problems

🌍 A Short History of Nasturtiums

The garden nasturtium travelled from the Andes to nearly every temperate garden on earth in a few short centuries, carried by its rare combination of beauty, edibility, and ease.

Nasturtium Growing FAQ

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